An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera

An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera

SAJB-02522; No of Pages 13 South African Journal of Botany xxx (2019) xxx Contents lists available at ScienceDirect South African Journal of Botany ...

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SAJB-02522; No of Pages 13 South African Journal of Botany xxx (2019) xxx

Contents lists available at ScienceDirect

South African Journal of Botany journal homepage: www.elsevier.com/locate/sajb

An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera B. Padayachee ⁎, H. Baijnath School of Life Sciences, University of Kwa-Zulu Natal, Private Bag X 54001, Durban, South Africa

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Article history: Received 29 March 2019 Received in revised form 2 July 2019 Accepted 7 August 2019 Available online xxxx Edited by NE Madala Keywords: Moringa oleifera Medicinal benefits Pharmacological attributes Phytochemistry Recent advances

a b s t r a c t Moringa oleifera Lam, or the horse-radish tree as it is commonly called is a pan-tropical species that has now become naturalized in Afghanistan, Florida and East and West Africa. In addition to its exceptional nutritional value in various parts of the world, M. oleifera is well-known for the substantial medicinal benefits that it offers. Scientific studies over the past few decades have substantiated many of the traditional folklore claims of the medicinal uses of morphological parts of M. oleifera for various ailments such as heart complaints, fevers, inflammation, digestive disorders, headaches, asthma, intestinal complaints and rheumatism. Moringa oleifera possesses many pharmacological attributes such as analgesic, anti-inflammatory, diuretic, antihypertensive, antioxidant and anti-tumor activities. In addition, M. oleifera also contains several phytochemicals, some of which are of high interest because of their medicinal value. Every part of M. oleifera is said to have beneficial properties which contribute to its diversity and value as a medicinal plant. This review will present an updated compilation of the published scientific evidence on the medicinal attributes, phytochemical composition and recent advances in pharmacognosy of M. oleifera. © 2019 SAAB. Published by Elsevier B.V. All rights reserved.

1. Introduction In addition to its compelling water purifying powers and nutritional benefits, M. oleifera is highly valued for its medicinal properties. A number of medicinal properties have been ascribed to various parts of this highly esteemed tree (Table 1). Almost all parts of the tree: root, bark, gum, leaf, fruit (pods), flowers, seed and seed oil have been used for various ailments in the indigenous system of medicine (Anwar et al., 2007). The extensive medicinal properties as well as the multiple array of pharmacological activities that it possesses make M. oleifera enormously beneficial and provides a powerful tool to contribute to health and medicine as a panacea for various ailments. Moringa oleifera is the most widely distributed species of the monogeneric family M. oleiferaceae that includes 13 species of trees and shrubs distributed in sub-Himalayan ranges of India, Sri Lanka, North Eastern and South Western Africa and Madagascar (Padayachee and Baijnath, 2012). It is commonly known in various Indian languages and in many regions as Sajina (Bengali); Horseradish tree, drumstick tree (English); Sahinjan, (Hindi); Murinna, (Malyalam); Sevaga (Marathi); Sobhanjana, (Sanskrit) and Sehjan (Urdu) (Fahey, 2005). It is found wild and cultivated throughout the plains and thrives best in tropical climates, and is abundant near the sandy beds of rivers and streams. ⁎ Corresponding author. E-mail address: [email protected] (B. Padayachee).

Considered to be a “Miracle tree” and “Tree of life” by many due to the substantial beneficial effects that it has on health, nutrition, water sanitation and the environment, M. oleifera has shown its diversity and potential as a valuable entity in many ways. It has a multitude of uses in medicine in various parts of the world. Traditional folk remedies prescribe an infusion of the leaves to treat conjunctivitis and as a poultice on the abdomen to expel intestinal worms. The fresh leaves of M. oleifera are beneficial for pregnant and lactating mothers as they improve milk production and are prescribed for anemia (Fuglie, 1999). The leaf juice is used to stabilize blood pressure and control glucose levels in diabetic patients. The roots, leaves and flowers of M. oleifera are used in traditional medicine for the treatment of diarrhea and hypertension in many countries (Anwar et al., 2007). The root powder is used as an aphrodisiac and, when mixed with milk, it is useful against asthma, gout, rheumatism and enlarged spleen or liver. Moringa oleifera preparations have also been cited in scientific literature as having a broad range of pharmacological activities; antimicrobial, hypotensive, hypoglycemic, immunomodulatory and antiinflammatory activities. For example, the seeds possess significant antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa (Council of Scientific and Industrial Research, 1962). The leaves are known to be potential source of natural antioxidants such as flavonoids, quercetin, β-sitosterol and zeatin. Moringa oleifera roots and leaves have been reported to possess antispasmodic activity (Aney et al., 2009). Hot water infusions of the leaves, seeds, flowers, roots and bark displayed anti-inflammatory activity (Guevara et al.,

https://doi.org/10.1016/j.sajb.2019.08.021 0254-6299/© 2019 SAAB. Published by Elsevier B.V. All rights reserved.

Please cite this article as: B. Padayachee and H. Baijnath, An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.08.021

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Table 1 Common medicinal uses and phyto-chemical composition of morphological parts of the M. oleifera tree. Plant part

Medicinal use

Traditional method of preparation

Phytochemical constituent

References

Root

Used as a laxative, astringent, diuretic, cardiotonic, abortifacient and rubefacient. Treats toothaches, common colds, external sores, inflammations, stomatitis, piles, bronchitis, urinary discharges, obstinate asthma, rheumatism, epilepsy. Useful for lower back and kidney pain and constipation and as a stimulant for nervous debility, paralytic afflictions, hysteria and epilepsy. Useful for heart complaints, eye diseases, fevers, inflammation, dyspepsia and enlargement of spleen. Relieves earaches, toothaches. Treats sores, colds, digestive disorders, hysteria, headaches. Used as an aphrodisiac. Used as an astringent, rubefacient and abortifacient. Used to relieve toothaches, headaches, fevers, intestinal complaints, dysentery and asthma. Treats syphilis and rheumatism. Used as an anti-helminthic and aphrodisiac. Treats hypocholesteremia, diarrhea, colitis and rheumatism. Reduces glandular swelling and headaches. Used for piles, fevers, constipation, bronchitis, ear and eye infections, scurvy and catarrh. Promotes digestion and used as a poultice for sores. Treats inflammations, bacterial infections, common colds, external sores/ulcers, throat infections, muscle diseases, tumors and cholera. Used as a diuretic, aphrodisiac, and abortifacient. Folk remedies or tumors Used as a tonic and against helminthes and skin tumors. Treats diabetes and joint pains.

Prepared as decoctions

Benzylglucosinolate Aurantiamide acetate 1,3 dibenzyl urea

Kirtikar and Basu (1975), Caceres and Lopez (1991), Dayrit et al. (1990), Vaidyaratnam (1994), Padmarao et al. (1996), Ruckmani et al. (1998), Fuglie (1999), Bennett et al. (2003), Sashidhara et al. (2009)

Decoctions for creams or emollients

Alkaloids (moringine; moringinine) Vanillin β-sitosterol Otacosanoic acid

Kerharo (1969), Satyavati and Gupta (1987), Faizi et al. (1994), Fuglie (1999), Siddhuraju and Becker (2003)

Used to season food preparations

Arabinose Galactose Glucoronic acid Rhamnose Mannose Leucoanthocyanin

Battacharya et al. (1982), Khare et al. (1997), Fuglie (1999), Fuglie (2001)

The leaves are cooked and used like spinach. Leaves are also commonly dried and crushed into a powder, and used in soups and sauces.

Catechol tannins Steroids Triterpenoids Flavonoids Saponins Anthraquinones Alkaloids Glucosinolate Carotenoids Ascorbic acid Vitamins Isothiocyanates Tannins

Dayrit et al. (1990), Caceres and Lopez (1991), Makkar and Becker (1996), Fuglie (1999), Ghasi et al. (2000), Verma et al. (2009), Kasolo et al. (2010), Muhammad et al. (2016)

Bark

Gum

Leaf

Flower

Pod

Seed

Seed oil

Cures eye diseases and head complaints. Used for treatment of fevers, snake bites, scorpion stings and warts. Treats ulcers, gastritis, skin disorders, bladder infections, scurvy, abdominal tumors and schistosomes. Removes harmful bacteria. Used as a purgative. Useful in leprosy and ulcers. Treats rheumatism, gout, skin pathogens, lupus and bladder disorders. Improves prostate function.

Galactose Glucoronic acid Ascorbic Flower extracts are used for preparations to enhance taste and acid Tocopherols Kaempherol, Rhamnetin, Isoquercitrin color in dishes. Kaempferitrin

Caceres and Lopez (1991), Nath et al. (1992), Asres (1995), Faizi et al. (1998), Pramanik and Islam (1998), Fuglie (1999), Siddhuraju and Becker (2003), Sanchez-Machado et al. (2006)

Young pods are sliced and boiled in water with salt. Mature pods are twisted open, are removed and fried in oil or cooked like pea, fresh or dried Seeds are prepared green, roasted or powdered, steamed and extracted as an oil

Nitriles Isothiocyanates β-sitosterol Galactose D-galacturonic acid L-arabinose L-rhamnose

Faizi et al. (1995), Faizi et al. (1998), Bharali et al. (2003), Fuglie (1999); Roy et al. (2007)

Benzylglucosinate Di-oleic-triglyceride Mono-palmitic acid

Memon and Khatri (1987), Satyavati and Gupta (1987), Caceres and Lopez (1991), Akhtar and Ahmad (1995), Fuglie (1999), Bennett et al. (2003), McBurney et al. (2004)

Used in water treatment and purification

Tocopherols Palmitic acid Stearic acid Arachidic acid Phenylacetonitrile

Dayrit et al. (1990), Caceres and Lopez (1991), Fuglie (1999), Anwar and Bhanger (2003)

1999). The different parts of M. oleifera such as the roots, leaves, flowers, fruits and seeds are also known to be good sources of phytochemicals/secondary metabolites. It is reported to contain alkaloids, flavonoids, carotenoids, tannins, anthraquinones, anthocyanins and proanthocyanidins (Goyal et al., 2007). These phytochemicals contribute to the healing properties of M. oleifera. In the last few decades there has been an exponential growth in the field of herbal medicine. These herbal medicines have maintained their popularity for both historical and cultural reasons. An abundance of the population in many developing countries often depends on medicinal plants for its health requirements. Many of these developing countries are located in the tropical and sub-tropical regions of the world where M. oleifera grows and is cultivated. Moringa oleifera has great potential in providing affordable and easily accessible medicinal value to communities in developing countries who are in need of proper healthcare, especially in areas where western medicine is inaccessible. If validated by medical science, dietary consumption of this plant could be advocated in these and other countries as an inexpensive prophylactic strategy against many diseases. The present review will provide an updated

review of the traditional medicinal uses, phytochemical composition and the recent advances with regard to pharmacological studies involving M. oleifera. 2. Medicinal attributes For centuries, people all over the world, including traditional healers, have prescribed different parts of the M. oleifera tree as traditional medicine. The medicinal uses are numerous and have been long recognized in Ayurvedic and Unani systems of medicine (Kumar et al., 2010). Among the myriad of natural plants that are investigated for their pharmacological properties, M. oleifera is regarded as one of the most important and beneficial because it is both a medicinal and functional food. Various parts of the tree such as the leaves, roots, seeds, pods, fruits and flowers are being used for treating common ailments such as skin infections, anemia, asthma, cough, diarrhea, swelling, headaches, hysteria, cholera, respiratory disorders, scurvy, diabetes, sore throat and chest congestion in the indigenous system of medicine. The numerous ethnomedicinal uses, phytochemical

Please cite this article as: B. Padayachee and H. Baijnath, An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.08.021

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constituents and traditional methods of preparing various parts of M. oleifera are summarized in Table 1. 3. Phytochemical studies Phytochemicals are non-nutritive plant chemicals that have protective or disease preventive properties. The Moringa family is rich in a combination of phytochemicals such as zeatin, quercetin, β-sitosterol, caffeoylquinic acid, kaempferol, kaempferitrin, Isoquercitrin, rhamnetin, rhamnose and in a fairly unique group of compounds called the glucosinolates and isothiocyanates (Fahey, 2005). HPLC and MS analyses showed the presence of gallic acid, chlorogenic acid, ellagic acid, ferulic acid, kaempferol, quercetin and vanillin from the aqueous extracts of leaves, fruits and seeds of M. oleifera (Singh et al., 2009). Studies have also shown the presence of polyphenols in the leaves and fruits of M. oleifera, with its content more enriched in the butanol fraction of the leaves and in the aqueous fraction of the fruits (Prasanth et al., 2011). The leaves were also reported to contain niazirin, niazirinin, 4-[(4’-O-acetyl-Lrhamnosyloxy) benzyl] isothiocyanate, niaziminin A, 3-caffeoylquinic and 5-caffeoylquinic acid as well as carotenoids, epicatechin and o-coumaric acid (Muhammad et al., 2016). The leaves of M. oleifera have also been cited as important sources of vitamins. Fresh leaves were reported to contain more vitamin C than the content of traditional sources such as oranges (Leone et al., 2015). A high content such as this is of great significance because of the function of vitamin C in facilitating the conversion of cholesterol into bile acids, hence lowering blood cholesterol levels; it also has antioxidant properties, protecting the body from detrimental effects of free radicals, pollutants and toxins. Vitamin E, in particular α-tocopherol is present in the leaves in amounts similar to the amount present in nuts. Vitamin E mainly functions as an antioxidant agent but it is also involved in the modulation of gene expression, inhibition of cell proliferation, platelet aggregation, monocyte adhesion and regulation of bone mass. Few vitamins among the B group; thiamine, riboflavin and niacin are present in M. oleifera leaves. These vitamins mainly act as co-factors of many enzymes involved in the metabolism of nutrients and energy production (Leone et al., 2015). Chemical investigations of ethanolic extracts of the seeds of M. oleifera indicated sterols, carbohydrates, alkaloids, glycosides and tannins; sterols and amino acids were identified by thin layer chromatography (TLC) (Rageeb and Usman, 2012). Gifoni et al. (2012) reported on the isolation of a thermostable chitin-binding protein named NH2CPAIQRCCQQLRNIQPPCRCCQ (Mo-CBP3) from the seeds of M. oleifera which displayed in vitro antifungal activity against the phytopathogenic fungi Fusarium solani, Fusarium oxysporum, Colletotrichum musae and Colletotrichum gloesporioides. The seeds also contain moringyne, 4-(áL-rhamnosyloxy) benzyl isothiocyanate and several amino acids (Gupta, 2008). The composition of the sterols of M. oleifera seed oil mainly consists of campesterol, stigmasterol, â-sitosterol, clerosterol and small quantities of 24-methylenecholesterol, stigmastanol and 28isoavenasterol (Anwar et al., 2007). Roy et al. (2007) reported on the isolation of a water-soluble polysaccharide from the aqueous extract of pods M. oleifera, which contains D-galactose, 6-O-Me-D-galactose, D-galacturonicacid, L-arabinose, and L-rhamnose. The flowers of M. oleifera are rich in calcium, potassium and antioxidants (α- and γ-tocopherol) (Makkar and Becker, 1996; Sanchez-Machado et al., 2006) and also contain nine amino acids, sucrose, D-glucose, traces of alkaloids, wax, quercetin and kaempferat. They have also been reported to contain flavonoid pigments such as alkaloids, kaempherol, rhamnetin, isoquercitrin and kaempferitrin (Faizi et al., 1994; Siddhuraju and Becker, 2003). A precipitate protein (PP) fraction from the flowers contains a mixture of aspartic, cysteine, serine and Ca2+−dependent proteases which exhibited caseinolytic and milkclotting activities (Pontual et al., 2012). Rajanandh and Kavitha (2010) revealed the presence of flavonoids and significant amounts of β-sitosterol in hydroalcoholic

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extracts of the leaves of M. oleifera, which could be responsible for its hypolipidemic and antioxidant properties. This was in line with a study by Shanmugavel et al. (2018) which revealed the presence of alkaloids, triterpenoids, flavonoids, tannins, saponins, glycosides and carbohydrates as well as a high content of vitamin C, which are of high therapeutic value and have both nutritional and medicinal properties. Phytochemical investigations by Kasolo et al. (2010) showed that ether, ethanol and water extracts of the leaves contain catechol tannins, gallic tannins, steroids, triterpenoids, flavonoids, saponins, anthraquinones, alkaloids and reducing sugars which contribute to its pharmacological value. Nepolean et al. (2009) identified several phytochemicals in the leaves of which the major compounds were; hexadecanoic acid, ethyl palmitate, palmitic acid ethyl ester, 2, 6-dimethyl-1, 7-octadiene-3-ol, 2-hexanone and 3-cyclohexyliden-4-ethyl-E2-dodecenylacetate. The gum of M. oleifera contains aldotriouronic acid which is obtained from the acid hydrolysis of gum and is characterized as O-(β-D-glucopyranosyluronic acid) (1 → 6)-β-D-galactopyranosyl (1 → 6)-D-galactose (Ram et al., 2006). Glucosinolates are also found in the bark of M. oleifera with only 4-(alpha-lrhamnopyranosyloxy)-benzylglucosinolate being detected in the bark tissue (Bennett et al., 2003). The roots of M. oleifera contain high concentrations of both 4-(alpha-l-rhamnopyranosyloxy)benzylglucosinolate and benzyl glucosinolate (Bennett et al., 2003). Sashidhara et al. (2009) isolated and characterized compounds; aurantiamide acetate 4 and 1, 3-dibenzyl urea 5 from the roots of M. oleifera, which was done for the first time from this species. Protective phytochemicals; gallic tannins, catechol tennins, steroids and triterponoids, saponins, anthraquinones, alkaloids, and reducing sugars were identified in ether, ethanol and aqueous extracts of the roots (Kasolo et al., 2010). 4. Pharmacological studies Specific components of M. oleifera preparations also possess many pharmacological activities such as: anticancer (Parvathy and Umamaheshwari, 2007; Masood, 2010); antiallergic (Madaka and Tewtrakul, 2011); antioxidant (Moyo et al., 2012b); anti-inflammatory (Cheenpracha et al., 2010); immunomodulatory (Sudha et al., 2010); antidiabetic (Jaiswal et al., 2009); antifungal (Chuang et al., 2007); antibacterial (Moyo et al., 2012a) and hepatoprotective (Buraimoh et al., 2011). An updated review of some important pharmacological activities ascribed to various parts of M. oleifera is detailed below. 4.1. Anti-inflammatory activity Inflammation is a very common symptom of many chronic diseases. It is the normal protective response of the body to tissue injury caused by physical trauma, chemical or microbial agents. Anti-inflammatory agents are responsible for remedying pain and reducing inflammation, thereby promoting health. Non-steroidal anti-inflammatory drugs are commonly used for the management of inflammatory conditions, but these are associated with many unwanted side effects such as gastric irritation, ulcers etc. The utilization of medicinal plants as antiinflammatory agents is considered to be a viable and logical alternative due to their safety and effectiveness (Alhakmani et al., 2013). There are reportedly 36 anti-inflammatory compounds all naturally occurring in the M. oleifera tree. Aqueous root extracts of M. oleifera (750 mg/kg) were shown to display anti-inflammatory activity by inhibiting carrageenan-induced edema in rats to a similar extent as the potent anti-inflammatory drug indomethacin (Ndiaye et al., 2002). The crude ethanolic extracts of the seeds reduced 85% of inflammation against carrageenan-induced hind paw edema in mice at a dose of 3 mg/kg body weight, while the mature seeds reduced edema by 77% of the same dose. Hot water infusions of the leaves, seeds, flowers, roots and bark also displayed similar activity

Please cite this article as: B. Padayachee and H. Baijnath, An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.08.021

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(Guevara et al., 1999). The anti-inflammatory activity was attributed to active compounds that are useful in the treatment of chronic and acute inflammatory conditions. Cheenpracha et al. (2010) reported on the anti-inflammatory activity of four phenolic glucosides from the ethyl acetate extract of M. oleifera fruits on the lipopolysaccharide (LPS)-induced murine macrophage RAW 264.7 cell line. Bacterial endotoxins such as LPS activate macrophages which cause the production of several molecules in the inflammatory process. One of these is nitric oxide (NO), known to be an important proinflammatory mediator in the activation of T lymphocytes and the increased vascular permeability observed in inflammatory processes. The results indicated that 4-[(2′-O-acetyl-α-L-rhamnosyloxy) benzyl]-isothiocyanate possessed potent nitric oxide inhibitory activity against LPS-induced nitric oxide release with an IC50 value of 1.67 μM; as well as 4-[(3′-O-acetyl-α-L-rhamnosyloxy)benzyl] isothiocyanate (IC50 = 2.66 μM); 4-[(4′-O- acetyl-α-L-rhamnosyloxy) benzyl] isothiocyanate (IC50 = 2.71 μM); followed by 4-[(α-L-rhamnosyloxy) benzyl] isothiocyanate (IC50 = 14.43 μM). The study indicated that the reported NO-inhibitory effect of M. oleifera fruits are attributed to these compounds (Cheenpracha et al., 2010). The M. oleifera seed extracts and lectins were evaluated for their in vitro anti-inflammatory activity using LPS-stimulated murine peritoneal macrophages (Araújo et al., 2013). Both lectins were able to reduce NO production by macrophages stimulated with LPS when compared with cells that had been exposed only to lipopolysaccharide. These results indicate that the in vitro anti-inflammatory activity of the aqueous seed extract and both lectins is due, at least in part, to the regulation of NO production. The aqueous seed and diluted seed extracts also significantly reduced (p b .05) the levels of TNF-α and IL-1β that were released by LPS-stimulated macrophages (Araújo et al., 2013). Another study on the seeds of M. oleifera examined its antiinflammatory activity on acetic acid-induced colitis in rats (Minaiyan et al., 2014). Low doses of M. oleifera seed hydro-alcoholic extracts (MSHE) and M. oleifera chloroform fractions were found to be effective in reducing inflammatory activity and were both effective in treating experimental colitis, which might be attributed to their similar major components, biophenols and flavonoids. They concluded that MSHE, even with low doses, could be considered as an alternative remedy for Irritable Bowel Disease (IBD) conditions and/or prevention of its recurrence. The flowers of M. oleifera were investigated by Alhakmani et al. (2013) for their anti-inflammatory activity using the protein denaturation method. Diclofenac sodium, a powerful non-steroidal antiinflammatory drug was used as a standard drug. The flower extracts (100–500 μg/mL) displayed a dose-dependent percentage inhibition of heat induced protein denaturation in fresh egg albumin which was comparable to the reference drug (100 and 200 μg/mL). 4.2. Antioxidant activity Antioxidants are molecules capable of supplying free atoms to the human body and inhibiting free radicals which damage cells and cause oxidative stress. They have also been shown to play a role in reducing the risk and progression of certain acute and chronic diseases such as cancer, heart diseases and stroke as well as in controlling the aging process. Medicinal plants are important sources of natural antioxidants. The drumstick leaves are reported to be a potential source of natural antioxidants such as flavonoids, quercetin, β-sitosterol and zeatin. Mature and tender leaf extracts were reported to have strong scavenging effects on free radicals, superoxide and nitric oxide radicals (Sreelatha and Padma, 2009). Methanolic extracts of the leaves showed good antioxidant activity (IC50 49.86 μg/mL) when compared to ascorbic acid (IC50 56.44 μg/mL), which is a well-known antioxidant (Sharma et al., 2012). The major bioactive compound of phenolics was found to be the dominant constituent of M. oleifera leaves that contribute to this activity (Pari et al., 2007). Methanolic extracts of the pods

also showed significant antioxidant activity against 2,2-diphenyl-1picrylhydrazyl (DPPH) free radicals and NO and was comparable to ascorbic acid (Mukeshbhai, 2011). Oil from the seeds showed antioxidant activity, higher than butylated hydroxyl toluene (BHT) and alpha-tocopherol (Lalas and Tsaknis, 2002). Luqman et al. (2012) reported on a comparative in vitro and in vivo analysis of the antioxidant activity of aqueous and ethanolic extracts of M. oleifera leaves and fruits. Their analysis of concentration and dose-dependent effects of the M. oleifera leaves and fruit were established on markers of oxidative stress, its safety profile in mice models, and correlation with antioxidant properties using in vitro and in vivo assays. They concluded that the ethanolic extract of the fruits showed the highest phenolic content, strong reducing power and free radical scavenging capacity. The antioxidant capacity of ethanolic extracts of both the fruits and leaves was higher in the in vitro assay compared to the aqueous extract which showed higher potential in vivo. Therefore, the aqueous extract appeared to be less effective when compared to the ethanolic extract, which could be attributed to the higher content of phenolics in the ethanolic extract of the leaves, and it is known that the higher polyphenols extraction yield corresponds with higher antioxidant activity, probably due to the combined action of the substances in variable concentrations and their high hydrogen atom donating abilities. Safety evaluation studies showed that ethanolic and aqueous extracts of both fruits and leaves were well tolerated by experimental animals with no toxicity of the extracts up to a dose of 100 mg/kg body weight (Luqman et al., 2012). Pakade et al. (2013) compared the antioxidant activity of the leaves and flowers of M. oleifera to that of selected vegetables in South Africa (cabbage, spinach, broccoli, cauliflower and peas). Total phenol content (TPC), total flavonoid content (TFC), reducing power and radical scavenging activity were examined using the DPPH method. The TPC of M. oleifera was shown to be almost twice that of the vegetables and the TFC was three times that of the selected vegetables. Reducing power and DPPH radical scavenging ability of M. oleifera leaves were also much higher than those of the selected vegetables. Pakade et al. (2013) concluded that M. oleifera is a better source of antioxidants than common vegetables. Antioxidant activities of M. oleifera leaf extracts with various solvents (methanol, ethyl acetate, dichloromethane, and n-hexane) were determined using DPPH and 2,2′-azino-bis 3-ethylbenzothiazoline-6sulphonic acid (ABTS) methods (Fitriana et al., 2016). Their findings were that the methanol extract showed the highest free radical scavenging activity (IC50 49.30 μg/mL) in the DPPH assay and IC50 11.73 μg/mL in the ABTS assay. 4.3. Antitumor and anticancer activity Medicinal plants have been well established as major sources of highly effective conventional drugs for the treatment of many forms of cancer. Plants are also widely used for the development of clinically useful antitumor compounds into anticancer agents (Kamuhabwa et al., 2000). One of the many advantages of using dietary or natural compounds as an adjuvant for cancer is that they display low toxicity and minimal adverse side effects. The aqueous leaf extract of M. oleifera showed potent anticancer activity by activating the apoptotic pathway in HeLa cells (Nair and Varalakshmi, 2011). Methanolic leaf extracts also showed cytotoxic activity against human multiple myeloma (U266B1) cells with an ID50 of 0.32 μg/mL (Parvathy and Umamaheshwari, 2007). Earlier studies have shown skin tumor prevention following ingestion of drumstick (M. oleifera seedpod) extracts, with a dramatic reduction in skin papillomas in a mouse model (Bharali et al., 2003). Singhal et al. (2012) evaluated the gum of M. oleifera as a carrier for colon specific drug delivery. The susceptibility of M. oleifera gum to colonic bacteria and drug release in the colon was also assessed using drug release studies with rat caecal contents. Their results showed that a formulation containing 30% and

Please cite this article as: B. Padayachee and H. Baijnath, An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.08.021

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40% of M. oleifera gum released a significant amount of the drug curcumin (45.89% and 34.79% respectively) into the environment of the colon. The 30% formulation was also susceptible to the enzymatic action of caecal content that caused better drug release (90.46%) in the presence of rat fecal contents Thus, M. oleifera gum extracts aid in the release of curcumin which allows more effectiveness in the treatment of colon cancer (Singhal et al., 2012). The in vitro antiproliferative activity of methanol and dichloromethane M. oleifera leaf extract on three types of human cancer cell lines; hepatocarcinoma (HepG2), colorectal adenocarcinoma (Caco-2) and breast adenocarcinoma (MCF-7) was evaluated using the 3-(4,5dimethylthiazol-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction assay. The in vitro cancer chemopreventive properties was also investigated using the established method, quinone reductase (QR) induction assay. In the MTT assay, the IC50 of the dichloromethane extracts varied from 112 to 133 μg/mL for HepG2, Caco-2 and MCF-7 cancer cells, but became more than 250 μg/mL for the methanol extract. Moringa oleifera extracts not only displayed antiproliferation on cancer cells, but also showed no toxicity towards normal cells. In the QR assay, the dichloromethane extract induced significant QR activity (CD value = 91.36 ± 1.26 μg/mL), while the methanol extract had no inductive effect. Both effects could be attributed to the presence of polyphenols and flavonoids (Charoensin, 2014). Jung (2014) also investigated the anticancer properties of the leaves of M. oleifera. Soluble cold distilled water extracts (300 mg/mL) were found to induce apoptosis, inhibit tumor cell growth, and lower the level of internal reactive oxygen species (ROS) in human lung cancer cells (A549) as well as other several types of cancer cells, suggesting that the treatment of cancer cells with M. oleifera leaves are able to significantly reduce cancer cell proliferation and invasion. They also displayed no toxicity towards normal cells. The research by Al Asmari et al. (2015) was the first of its kind to evaluate the antimalignant properties of M. oleifera, collected from the Saudi Arabia region, not only in leaves but also in bark and seed extracts. When analyzed against breast (MDA-MB-231) and colorectal (HCT-8) cancer cell lines for cell survival, apoptosis and cell cycle progression, the extracts of the leaves and bark showed remarkable anticancer properties while surprisingly, seed extracts exhibited hardly any activity. Their GC–MS analyses revealed numerous anticancer compounds present in the extracts of the leaves and bark, however no significant anticancer compounds in the seed extracts. Specific components of M. oleifera preparations have also shown to exhibit anticancer activity. It was suggested that flavonoid or alkaloid compounds similar to the anticancer compounds vincristine and vinblastine may be present in M. oleifera leaves that could be used in the herbal treatment of myeloma patients (Parvathy and Umamaheshwari, 2007). A recent study has shown that phenolics and flavonoids namely, quercetin and kaempferol present in the fractions of M. oleifera extracts may act as potential agents for cancer chemoprevention with respect to reduced proliferation of human carcinoma cancer through the induction of in vitro apoptosis (Sreelatha et al., 2011). In addition, quercetin and quercetin-50,8disulfonate were shown to possess strong antitumor activity against MCF-7 human breast cancer cells via a ROS-dependent apoptotic pathway, hence quercetin and its derivatives show promise as anticarcinogenic agents and have excellent potential to be developed into an antitumor precursor compound (Zhang et al., 2012). 4.3.1. Mechanisms of action of the anticancer activity of Moringa oleifera Sreelatha et al. (2011) conducted an in-depth study on the cytotoxic effects as well as induction of apoptosis of M. oleifera leaf extracts on cancerous KB cells. The leaf extracts significantly inhibited KB cell proliferation in a dose-dependent manner. Some of the morphological changes observed in treated cells were cytoplasmic membrane shrinkage, loss of contact with neighboring cells, membrane blebbing, and apoptotic body formation. Cells treated with 200 μg/mL of M. oleifera leaf extract were stained with Propidium iodide (PI) to detect any changes

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to the nuclei of live and dead cells. These cells showed nuclear shrinkage, DNA condensation, and fragmentation, showing signs of apoptosis. They went a step further to quantify the apoptosis in the treated cells by determining the apoptotic index. Cells were treated with 4′,6diamidino-2-phenylindole (DAPI), which binds to the AT region of DNA to form a fluorescent complex and allows detection of abnormal nuclei, such as condensed or fragmented chromatin. The cells treated with the leaf extract showed the presence of nuclear apoptotic bodies and chromatin condensation, which confirmed the PI results. Agarose gel electrophoresis was also performed to determine if the DNA was compromised. Cells treated with the leaf extract had fragmented DNA and produced a smear of DNA fragments on the gel. It is probable that apoptosis was caused by an increase in reactive oxygen species (ROS) in the mitochondria. The levels of ROS in cells treated with the leaf extract were measured by the dichlorodihydrofluorescein diacetate (DCFH-DA) assay. Cells treated with 200 μg/mL of leaf extract showed a 350% increase in ROS compared to the negative control. Thus, this study confirmed the strong anticancer activity of leaf extracts of M. oleifera against KB cells and indicates that KB cell apoptosis is achieved by increasing ROS levels in the cell and fragmenting cellular DNA (Sreelatha et al., 2011; Khor et al., 2018). The mechanism of action of the anticancer activity of M. oleifera leaf extract on A549 lung cancer cells was evaluated by Madi et al. (2016). Different assays were conducted to investigate the mode of action and possible pathways which would cause anticancer cancer activity. The p-nitro-blue-tetrazolium salt assay showed a significant increase in ROS levels with increased concentration of the leaf extract. The adenosine triphosphate (ATP) bioluminescence assay was conducted which revealed a significant decrease in ATP levels with increasing M. oleifera leaf extract concentration. Glutathione (GSH) levels were significantly reduced with increasing extract concentration, as shown by the ApoGSH colorimetric test. The decrease of GSH together with the increase in ROS and decrease in ATP with increasing extract concentration suggests that the leaf extract compromises the mitochondrial pathway of the cell to induce cell death. The leaf extract was shown to induce mitochondrial membrane potential depolarization, measured using cellpermeable lipophilic JC-1 staining. Western blot analysis was then used by Madi et al. (2016) to determine if there were any changes in protein expression of the apoptotic markers; tumor protein p53, apoptotic inducible factor (AIF), cytochrome c, and SMAC/DIABLO (second mitochondria derived activator of caspases). All of these apoptotic markers showed increased expression in treated cells, which indicates higher levels of apoptosis in the cells. A549 cells treated with leaf extract also displayed elevated levels of lactate dehydrogenase (LDH), which indicates an increase in cell death. Apoptosis in cells was then measured using the FLICA assay, which is an immunofluorescent detection method that stains caspase proteins that are produced to activate apoptosis in cells. After 24 h of treatment, many cells fluoresced, indicating the presence of activated caspase and the activation of apoptosis in the cells. Hence, it was surmised that M. oleifera leaf extracts induces apoptosis in A549 cells via depolarization of the mitochondrial membrane, leading to a decrease in ATP, which in turn causes an increase in ROS levels and decrease in GSH levels, eventually causes the cells to undergo apoptosis (Madi et al., 2016; Khor et al., 2018). In another study, Berkovich et al. (2013) tested the effects of leaf extracts of M. oleifera on the pancreatic cancer cell lines Panc-1. The XTT assay showed that the extract had an inhibitory effect on cell proliferation. Flow cytometry analysis was done to evaluate the effects of the leaf extract on the cell cycle of treated cells. Treated and control cells were stained with PI to detect changes in the cell nucleus. Treated cells showed high proportions of cells in the sub-G1 phase, which increased with increasing concentration of leaf extract. Western blot analysis was then performed to detect levels of proteins p65, p-IkBα, and IkBα which are involved in the nuclear factor kappa B (NF-kB) signaling pathway. NF-kB is a proinflammatory transcription factor, and its signaling pathway plays a significant role in the resistance of pancreatic cancer cells to

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apoptosis-based chemotherapy. Cells treated with the leaf extract showed a significant reduction of the proteins compared to untreated cells, which indicates that the leaf extract can downregulate the NF-kB pathway in Panc-1 cells. Finally, the Panc-1 cells with M. oleifera leaf extract was treated in conjunction with a conventional anticancer drug, cisplatin, to determine if their interactions were additive, antagonistic, or synergistic. The Western blot results showed a synergistic effect and based on the results, it was concluded that M. oleifera extract was in fact, cytotoxic to Panc-1 cells and there is a possibility of using it in conjunction with cisplatin to greatly improve the effectiveness of the drug (Berkovich et al., 2013; Khor et al., 2018). 4.4. Antibacterial and antifungal activity Interest in medicinal plants with antimicrobial properties and microbial compounds has increased as a result of antimicrobial resistance. This resistance could be attributed to indiscriminate use of commercial drugs or undesirable side effects of certain antibiotics. The high cost of conventional drugs has also led to the increased use of plants as an alternative for treatment of infectious diseases. Plant extracts and phytochemicals with antimicrobial properties are of great importance in therapeutic treatments (Moyo et al., 2012a). Parts of M. oleifera have shown significant antimicrobial potential. Doughari et al. (2007) and Vinoth et al. (2012) showed that aqueous and ethanolic leaf extracts of M. oleifera displayed antibacterial activity against Salmonella spp. while the acetone leaf extracts at a concentration of 5 mg/ml displayed activities against Escherichia coli, Enterobacter cloacae, Proteus vulgaris, Staphylococcus aureus and Micrococcus kristinae with M. kristinae as the most susceptible since its growth was inhibited at 0.5 mg/mL (Moyo et al., 2012a). The antibacterial activity was attributed to the presence of saponins, tannins, phenols and alkaloid phytoconstituents. Napolean et al. (2009) reported Enterobactor spp, Staphlococcus aureus, Psuedomonas aeruginosa, Salmonella typhi and Escherichia coli to be sensitive to ethanol, chloroform and aqueous extracts of M. oleifera leaves at a concentration of 200 mg/L. Raj et al. (2011) showed that petroleum ether extracts of M. oleifera roots inhibit P. aeruginosa (13.1 ± 0.1 mm), S. aureus (16.0 ± 0.2 mm) and E. coli (10.2 ± 0.2 mm). Ethanol extracts showed activity against P. aeruginosa (12.1 ± 0.1 mm), S. aureus (11.0 ± 0.2 mm), E. coli (9.2 ± 0.2 mm) and Proteus mirabilis (8.1 ± 0.1 mm) while the chloroform and aqueous extracts were active against P. aeruginosa (12.2 ± 0.2 mm and 11.2 ± 0.2 mm) and E. coli (10.1 ± mm and 8.2 ± 0.3 mm). Vieira et al. (2010) reported efficient inhibitory effects on S. aureus (19–25 mm), Vibrio cholera (21–25 mm) and Escherichia coli (16–23 mm) by aqueous extracts of M. oleifera seeds. Rahman et al. (2009) showed that the fresh leaf juice, powder from fresh leaf juice and cold water extracts of the fresh leaf, displayed potential antibacterial activity against all the tested four Gram negative bacteria: Shigella shinga, Shigella sonnei, Pseudomonas aeruginosa, and Pseudomonas spp. and six Gram-positive bacteria: Staphylococcus aureus, Bacillus cereus, Streptococcus-B-haemolytica, Bacillus subtilis, Bacillus megaterium and Sarcina lutea. Antifungal activity was displayed by aqueous leaf extracts of M. oleifera against Penicillium spp., (13.0 ± 0.2 mm) and by petroleum ether extracts against Mucor spp., (12.0 ± 0.2 mm) at a concentration of 15 mg/ml. Ethanol extracts inhibited fungal pathogens Candida albicans (10.0 ± 0.1 mm), Penicillium spp., (9.1 ± 0.1 mm) and Mucor spp., (9.1 ± 0.3 mm). The phytochemical screening revealed the presence of alkaloids, flavonoids, saponins, terpenoids, steroids, tannins, cardioglycosides, amino acids and proteins which could serve as a natural source of antimicrobials (Raj et al., 2011). Ishnava et al. (2012) reported maximum antifungal activity of methanol extracts of M. oleifera (25 mm) against Trichoderma harzianum while Shukla et al. (2012) reported moderate to high antifungal activity ranging from 70% to 80% against an aflatoxin B1-producing strain of Aspergillus flavus by methanolic leaf extracts of M. oleifera.

These findings suggest that the ability of M. oleifera extracts to inhibit the growth of some strains of bacteria and fungi is an indication of its potential to either block or circumvent resistance mechanisms against pathogens and thus improve treatment and eradication of microbial strains (Moyo et al., 2012a). 4.5. Immunomodulatory activity Immunomodulation using plants is of primary interest in scientific communities because it provides an alternative to conventional chemotherapy for a wide range of diseases. It is based on the ability of the plants to effectively modulate immune functions, thus being able to promote positive health and maintain the resistance of the body to infection. Both aspects of immunomodulation i.e. immunostimulation and immunosuppression are equally important to regulate normal immunological functioning (Padayachee et al., 2012). The immunomodulatory action of the methanolic extract of M. oleifera leaves was evaluated in an experimental model of cellular and humoral immunity in mice (Sudha et al., 2010). The administration of two doses of the extracts (250 and 750 mg/kg, po) significantly increased the levels of serum immunoglobulins and also prevented the mortality induced by bovine Pasteurella multocida in mice. They also significantly elevated circulating antibody levels in the indirect hemagglunation test. Moreover, M. oleifera extracts produced a significant increase in adhesion of neutrophils, attenuation of cyclophosphamide-induced neutropenia and an increase in phagocytic index in the carbon clearance assay. It was surmised that methanolic extracts of M. oleifera are able to stimulate both the cellular and humoral immune response in mice and that low doses of the extracts were found to be more effective than the high dose. This could be due to the presence of compounds such as isothiocyanate and glycoside cyanides (Sudha et al., 2010). Research by Rachmawati and Rifa'I (2014) assessed the effects of aqueous extracts of M. oleifera leaves on the population of T cells (CD4+ and CD8+) and B cells (B220+) in Mus musculus mice in vitro. The aqueous extracts showed immunostimulatory activity as a result of its increase in the number of CD4+ (T helper cells), CD8+ (T cytotoxic cells) and B220+ cells at different doses. The highest cell proliferation of CD4+ and CD8+ cells was exerted by the lowest dose (0,1 μg/mL), while proliferation of B220+ cells was exerted by the highest dose (10 μg/mL). Immunostimulatory activity found by the increasing number of CD4+, CD8+ and B220+ was due to the active substances such as saponins and flavonoids in M. oleifera. Cell proliferation induced by lymphocyte responses can be caused by exogenous stimuli in the form of the active compounds of plants which act as immunostimulators. This immunostimulatory activity was attributed to the active compounds saponins and flavonoids found in M. oleifera which act as MAPK (mitogen-activated protein kinase), stimulating T- and B cell proliferation through the expression of Interleukin-2 and also stimulating antibody synthesis. Flavonoids exert an antioxidant effect which stimulates the immune system through an inflammatory reaction while saponin increases the production of immune mediators which plays a role in the immune system (Rachmawati and Rifa'I (2014)). Gupta et al. (2010) reported that ethanolic leaf extracts of M. oleifera showed immunomodulatory activity on mice by causing a significant reduction in cyclophosphamide-induced immunosuppression. Their results indicated a significant increase in the WBC count, phagocytic index, percent neutrophils and weight of the thymus and spleen in normal mice after chronic administration of the extracts. Both humoral and cell-mediated immunity were stimulated by the extracts, of which the exact mechanism of action is not clear, but may be due to an enhanced production of growth factors. The phytochemical constituents present in significant amounts in M. oleifera may be responsible for its immunomodulatory activity (Gupta et al., 2010). Thus, it was shown that M. oleifera extracts may alleviate the myelosuppression and subsequent leucopenia induced by cylophosphamide in mice.

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These results were validated by the work of Banji et al. (2012) who also showed a substantial elevation in neutrophil adhesion and phagocytic activity in mice following treatment with ethanolic extracts (200 mg/kg) and hydro-alcoholic extracts (100 and 200 mg/kg) of the leaves of M. oleifera. An increase in humoral antibody levels and in total leukocytes was observed. The hydro-alcoholic extracts (200 mg/kg) also produced a significant increase in delayed type hypersensivity response in rats. Anudeep et al. (2016) evaluated the immunomodulatory effects of soluble dietary fiber, from the seeds of M. oleifera, characterized as a resistant protein (MSRP). Immunostimulatory activity of MSRP was assessed by murine splenocyte proliferation and production of NO from macrophages. MSRP at low concentrations (0.01 μg/well) significantly increased the proliferation of splenocytes and induced a 6-fold increase in NO production when compared to the control, indicating the activation of macrophages. A polysaccharide isolated from the aqueous extracts of mature pods of M. oleifera showed immunoenhancing properties by increasing macrophage activity through the release of nitric oxide on a mouse monocyte cell line (J7441). It also demonstrated immunomodulatory activity in the rohu fish (Labeo rohita) by increasing total serum proteins, albumins and globulins when compared to the control fish (Mondal et al., 2004). Research by Kurokawa et al. (2016) examined the antiherpetic action of aqueous extracts of leaves of M. oleifera. In this study, they evaluated the alleviation of herpetic skin lesions by the aqueous extract (AqMOL) and assessed the mode of its antiherpetic action in a murine cutaneous herpes simplex virus type 1 (HSV-1) infection model. The extracts (300 mg/kg) was administered orally to HSV-1-infected mice three times daily on days 0–5 after infection. It was found that M. oleifera extracts significantly limited the development of herpetic skin lesions and reduced virus titers in the brain on day 4 without toxicity. Infected mice that were administered the extract also displayed a strong delayed-type hypersensitivity (DTH) response to inactivated HSV-1 antigen, and elevated interferon (IFN)-γ production by HSV-1 antigen at 4 days post-infection. The extracts were also effective in elevating the ratio of CD11b+ and CD49b+ subpopulations of splenocytes in infected mice (Kurokawa et al., 2016). 4.6. Antidiabetic activity Diabetes mellitus is the most common metabolic disorder worldwide and is a major public health problem. It results in hyperglycemia which later develops into microvascular and macrovascular complications, often leading to death. Synthetic oral agents and insulin therapy are used to treat hyperglycemia however, these agents produce detrimental side effects and are very expensive for impoverished populations, especially in developing countries. Hence, there will always be the need to search for cost-effective and efficient hypoglycemic agents with fewer side effects. Herbal preparations have been used for centuries for the treatment of diabetes in different societies and, scientific research has substantiated the antidiabetic properties of some medicinal plants (Edoga et al., 2013). A survey conducted by Dieye et al. (2008) on the use of medicinal plants for the treatment of diabetes in Senegal revealed that, of 41 plant species used by patients to treat diabetes, M. oleifera was the most frequently cited plant. The antidiabetic activity of the fruits, leaves and pods of M. oleifera has been previously recorded in literature (Rana et al., 1999) Many studies have evaluated the antidiabetic activity of M. oleifera in experimental animals. The powder, aqueous, ethanol and methanol extracts of M. oleifera seeds, roots and stem bark were shown to provide good glycemic control in diabetic animal and human models (Muhammad et al., 2016). Gupta et al. (2012) reported on the antidiabetic effects of methanol extracts of M. oleifera pods (MOMtE) in streptozotocin (STZ)-induced diabetic albino rats. After treatment of the rats with 150 or 300 mg/kg MOMtE for 21 days, the

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progression of diabetes was significantly reduced as indicated by the reduction in serum glucose and nitric oxide as well as concomitant increases in serum insulin and protein levels. Edoga et al. (2013) investigated the antidiabetic activity of the leaves of M. oleifera on albino rats. Hyperglycemia was induced in rats using alloxan (120 mg/kg body weight), intraperitioneally. Normoglycemic and hyperglycemic rats were treated with three different doses of the aqueous extracts as well as tolbutamide (positive control) and normal saline (negative control). The aqueous extract produced a dose-dependent reduction in blood sugar levels of normoglycemic and hyperglycemic rats. In normoglycemic rats, the aqueous extract of M. oleifera (100, 200 and 300 mg/kg) exhibited 23.14%, 27.05% and 33.18% reduction of the blood glucose levels within 6 h of administration respectively, while tolbutamide (200 mg/kg) showed 33.29% reduction. In hyperglycemic rats, the aqueous extract (100, 200, 300 mg/kg) displayed 33.29%, 40.69% and 44.06% reduction of blood glucose concentration within 6 h of administration respectively, while tolbutamide (200 mg/kg,) caused 46.75% reduction. Hence the antidiabetic activity is comparable with that of the reference drug (Edoga et al., 2013). Sunilkumar (2011) investigated the antidiabetic activity of hydroalcoholic extracts of M. oleifera flowers on streptozotocin (65 mg/kg)-induced Type 1 diabetic and alloxan (120 mg/kg)-induced Type 2 diabetic rats. It was found that the extracts constantly maintained significant reduction of glucose levels in the streptozotocinand alloxan-mediated diabetic rats throughout the experimental period, suggesting its antihyperglycemic properties. The extracts also increased the body weight of diabetic rats when compared to control rats, which may be due to the protective effects of the extracts in causing the reversal of gluconeogenesis. Phytochemical screening revealed the presence of flavonoids and tannins in the extracts which may be attributed to the observed antidiabetic activity (Sunilkumar, 2011). Al-Malki and El Rabey (2015) evaluated the antidiabetic activity of two low doses of M. oleifera seed powder (50 and 100 mg/kg body weight, in the diet) on streptozotocin-induced diabetes (Type I) in male rats. Lipid peroxide levels were significantly reduced in the diabetic rats when compared to the positive control group, with the lower dose of M. oleifera seeds having a more pronounced effect. Immunoglobin (Ig) A, Ig G, Interleukin (IL)-6 as well as Hemoglobin A1c levels were also reduced, with the higher dose of M. oleifera being more effective than the lower dose in all parameters. Fasting blood sugar levels were also reduced although being higher than the negative control values. They concluded that treating the diabetic rats with both doses of M. oleifera powder ameliorated the levels of all these parameters approaching the negative control values and restored the normal histology of both the kidney and pancreas compared with that of the diabetic positive control group. It was also found that the antidiabetic activity of the higher dose (100 mg/kg b.w.) was more efficient than that the lower dose (50 mg/kg b.w.) Jaiswal et al. (2009) assessed the antidiabetic activity of the aqueous leaf extracts of M. oleifera (200 mg/kg) in streptozotocin (STZ)-induced sub, mild and severely diabetic rats. The dose of 200 mg/kg decreased blood glucose levels (BGL) of normal animals by 26.7% and 29.9% during fasting blood glucose (FBG) and oral glucose tolerance test (OGTT) studies respectively. In sub and mild diabetic animals, the extracts produced a maximum decrease of 31.1% and 32.8% respectively, during OGTT studies. In the diabetic animals FBG and post prandial glucose (PPG) levels were reduced by 69.2% and 51.2% whereas, total protein, body weight and hemoglobin were increased by 11.3%, 10.5% and 10.9% respectively after 21 days of treatment. Significant reduction was also found in urine sugar and urine protein levels. Hence, it was shown that the leaves of M. oleifera have significant hypoglycemic and antidiabetic potential and warrant further investigation into the pharmacological and biochemical properties to elucidate the mechanism of action (Jaiswal et al., 2009). A few studies have evaluated the antidiabetic activity of M. oleifera in humans. Kumari (2010) reported the hypoglycemic effect of M. oleifera

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leaf dietary consumption over a 40-day period in untreated Type 2 diabetes patients, between the ages of 30–60 years. The experimental group included 46 subjects, 32 men, and 14 women and the control group included 9 subjects, 4 men and 5 women. The experimental group received a daily dose of 8 g M. oleifera leaf powder. Daily meals among both groups were comparable in terms of relative content of food types, nutrients and calories received. Results showed that fasting plasma glucose (FPG) levels and post prandial blood glucose (PPPG) levels did not vary much from baseline in the control group, however, they were significantly reduced in the experimental group (FPG: −28%; PPPG: −26%). Ghiridhari et al. (2011) studied the hypoglycemic effect of M. oleifera leaf tablets on a group of 60 Type 2 diabetes patients, age 40–58 years, treated with sulfonylurea medication and on a standardized calorierestricted diet. Moringa oleifera leaf powder constituted 98% of the tablet content. Patients in the experimental group received two M. oleifera leaf tablets/day, one after breakfast and one after dinner for 90 days. Blood glycated hemoglobin (HbA1c) was measured before and after the treatments. In the control group, HbA1c and PPPG levels reduced over time but with no significant change. In the experimental group, relative to the baseline, HbA1c decreased by 0.4% (from 7.8 ± 0.5 to 7.4 ± 0.6 mg/dL). PPPG levels in the experimental group progressively decreased with treatment duration, by 9% after 30 days, 17% after 60 days, and 29% after 90 days, indicating that M. oleifera treatments can induce better glucose tolerance over time. 4.7. Hepatoprotective activity The liver, a vital organ performs a wide range of important functions including detoxification and protein synthesis, and if these functions are compromised by many substances we are exposed to, the consequences can be life threatening. Liver disease is a worldwide problem. Many of the drugs used conventionally to treat liver diseases are inadequate and have serious detrimental effects. The search for effective hepatoprotective drugs often focuses on medicinal plants which play a role in the management of various liver disorders (Buraimoh et al., 2011). Buraimoh et al. (2011) investigated the hepatoprotective effect of the ethanolic leaf extract of M. oleifera on the histology of paracetamol-induced liver damage. Wistar rats treated with 500 mg/kg of the extracts showed reduced necrotic cell damage and wider sinusoidal spaces when compared to the negative control group that showed marked distorted hepatic cords, necrotic cells and obliterated sinusoids. Kumar et al. (2010) examined the hepatoprotective activity of methanolic extracts of the leaves and flowers of M. oleifera against carbon tetrachloride (CTL)-induced hepatotoxicity in rats using histopathological parameters. The extract at an oral dose of 250 mg/kg exhibited a significant protective effect by lowering the serum levels of bilirubin, glutamate pyruvate transferase (SGPT), glutamate oxaloacetate transferase (SGOT), alkaline transferase and lysosomal enzymes. The liver section of the extract-treated groups also showed normalization of the cellular degeneration caused by CTL and was also comparable to that of silymarin, a known hepatoprotective agent. The coumarin fraction of the methanolic extract also showed significant hepatoprotective activity by normalizing changes in biochemical hepatic enzymes produced by CTL and also normalizing levels of lysosomal enzymes in the blood. Kumar et al. (2010) suggested that a hepatoprotective action may be due to the ability of the coumrin fraction to inhibit inflammatory mediators and prevent cellular injury. Various concentrations of crude aqueous and ethanolic extracts of M. oleifera were examined on carbon tetrachloride (CCl4) hepatocyte induced injury in rats and compared with the standard drug silymarin at concentrations of 0.001, 0.005 and 0.01 mg/mL (Rameshvar et al., 2010). Results showed that the extract was effective in reducing CCl4induced enhanced activities of glutamic oxaloacetic transaminase (GOT), glutamate pyruvate transaminase (GPT), lipid peroxidation and % viability. Low concentrations (0.01 mg/L) of the ethanolic extract

had significant hepatoprotective activity while that of aqueous extracts were effective at higher concentrations (0.1 mg/L) of the drug. The recovery of hepatocellular injury by pretreatment with the crude extract of the leaves, suggest that it shows prominent hepatoprotective activity as compared to the standard drug. Toppo et al. (2015) examined the hepatoprotective activity of M. oleifera leaves against cadmium-induced toxicity in Wistar albino rats. Control group rats received oral doses of cadmium chloride and experimental rats were co-treated with M. oleifera extracts (500 mg/kg) and cadmium chloride for 28 days. Treatment with M. oleifera significantly decreased the elevated aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), lipid peroxidation (LPO) and increased superoxide dismutase (SOD) levels. The reversal of elevated serum intracellular enzyme levels by the M. oleifera extract may be attributed to the stabilizing ability of the cell membrane preventing enzyme leakages also to hepatoprotective properties of the plant, possibly attributed to the presence of flavonoids such as quercetin and kaempferol, vitamin A and ascorbic acid in M. oleifera (Toppo et al., 2015). Based on research conducted by Fakurazi et al. (2008), the hepatoprotective properties of M. oleifera leaf extracts were elucidated against a single high dose of acetaminophen (APAP) induced hepatotoxicity in Sprague Dawley rats. The rats were treated with APAP (3000 mg kg−1bw) to induce hepatocellular damage and were pretreated with M. oleifera extracts (200 and 800 mg kg−1). Treated rats showed a reduction of liver enzymes (ALT, AST and ALP) and also the restoration of glutathione levels. The biochemical results showed a parallel finding with the histopathological analysis in which, liver sections that were obtained from rats and pretreated with MO displayed a reduction in damage. They concluded that M. oleifera has promising potential by enabling protection of the liver against APAP-induced liver injury via the restoration and elevation of glutathione levels. 4.8. Cardiovascular activity Cardiovascular disease (CVD) is a wide spectrum of diseases and conditions involving the heart and blood vessels, and is the first cause of mortality worldwide. Medicinal plants have been used for the treatment of CVD for millennia. This may be attributed to their ability to act as antioxidants, vasodilators, adrenoceptor and platelet activating factor (PAF) antagonists. Many therapeutic treatments for the cardiovascular activities of some of these plants have been explored in patients with hypertension, hyperlipidemia, thromboembolism, coronary heart disease, congestive heart failure, angina pectoris, atherosclerosis, cerebral insufficiency, venous insufficiency, arrhythmia, etc. Hence, there is an increasing need to consider plant-based treatment modalities because of their potential benefits. Several studies in animal and human models will be reviewed. Chumark et al. (2008) examined the therapeutic potential of M. oleifera leaves on dyslipidemia induced in rabbits on a highcholesterol (5%) diet (HCD) for 12 weeks. After the treatment regimen, the HCD-fed rabbits experienced elevations in the plasma levels of total cholesterol (TC), high density lipoprotein (HDL-C), low density lipoprotein (LDL-C), and triglycerides (TG). The diet also caused extensive plaque formation in carotid arteries. HCD rabbits that were administered with M. oleifera aqueous extract at a daily dose of 100 mg/kg b.w. for the duration of the protocol displayed a reduction in the above-mentioned elevations: TC by 50%, lipoprotein-cholesterol by 50%, TG by 75%, and plaque formation by 97%. This protective effect was comparable to that of the anticholesterol drug simvastatin, given at a daily dose of 5 mg/kg b.w. Similar results were also achieved by Mehta et al. (2003) when HCD rabbits were administered with aqueous extracts of M. oleifera fruits and by Jain et al. (2010) when HFD albino rats were administered methanolic extracts of M. oleifera leaves. Obesity is defined as abnormal or excessive fat accumulation triggered by disproportion in energy intake and expenditure and has

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emerged as a major health problem and risk factor for various disorders worldwide. Obesity has been found to be associated with various disorders such as osteoarthritis, ischemic heart diseases, atherosclerosis, diabetes, and hypertension (Panico and Iannuzzi, 2004). Bais et al. (2014) studied the antiobesity activity of methanolic extracts of M. oleifera leaves (MEMOL) in high fat diet-induced obesity (HFD) in rats. HFD rats displayed hypercholesterolemia (116.2 ± 0.27 mg/dL), causing an elevation in body weight (225 g), TC (116.2 ± 0.271 mg/dL, TG, (263.0 ± 4.69 mg/dL) and LDL (61.68 ± 2.94 mg/dL) as well as in blood glucose (94.1 ± 4.9 mg/dL). Obese rats that were treated with MEMOL (200 mg/kg and 400 mg/kg) significantly attenuated the levels of TC (98.16 ± 0.52 mg/dL and 87.620 ± 0.543 mg/dL respectively), TG (246.5 ± 8.65 mg/dL and 242.92 ± 6.58 mg/dL), LDL (48.4 ± 5.5 mg/dL and 45.25 ± 5.2 mg/dL) and increased levels of HDL (35.76 ± 1.31 mg/dL 46.71 ± 2.381 mg/dL). Hence, treatment with MEMOL for 3 weeks reversed the hyperlipidemic effect produced by high-fat diet significantly and similar results were obtained with the standard drug. Treatment with MEMOL also reduced blood glucose levels and liver biomarkers and were able to prevent body weight gain, concomitantly helping in maintaining the current body weight. Further, the extracts significantly reduced the atherogenic index, which is regarded as a marker for various cardiovascular disorders, thus providing cardioprotection (Bais et al., 2014). Randriamboavonjy et al. (2016) assessed the cardiac effects of oral administration of M. oleifera seed powder in spontaneous hypertensive rats (SHR). SHR received food containing the powder (750 mg/day, 8 weeks) or normal food. In vivo measurements of hemodynamic parameters were then performed. The results showed that M. oleifera treatments did not modify blood pressure in SHR but reduced the nocturnal heart rate and improved cardiac diastolic function. Left ventricular (LV) anterior wall thickness, inter-septal thickness on diastole, and relative wall thickness were reduced after treatment as well. They also found a significant reduction of fibrosis in the left ventricle of M. oleifera treated SHR. They associated the afore-mentioned antihypertrophic and antifibrotic effect with increased expression of peroxisome proliferator-activated receptor (PPAR)-α and -δ, and an elevated level of plasmatic prostacyclins. The extracts also improved ejection volume and cardiac output in SHR. The authors suggested that the beneficial effects of M. oleifera seed powder on cardiac function in rats may be attributed to their effects on signaling pathways involved in pressure overload-induced LV hypertrophy, specifically, calcium handling mechanisms, and singled out the calmodulin-activated serine–threonine protein phosphatase calcineurin pathway as a potential target of M. oleifera. This could be due to the fact that calcineurin activity was shown to progressively increase with age in the heart of SHR and the inhibition of calcineurin reduces hypertrophy development. Their research validated the empirical use of the plant to treat cardiac complications due to blood pressure overload. In a study by Nambiar et al. (2010), the potential antidyslipidemic effects of M. oleifera was investigated in 35 hyperlipidemic human subjects involving 26 men and 9 women. The control and experimental groups consisted of 18 subjects and 17 subjects, respectively. The experimental group was administered a daily total of M. oleifera leaf tablets (550 mg) twice daily for 50 days. Plasma lipid levels were determined before and after the treatment. Compared to the control group, the experimental group displayed a 1.6% decrease in plasma TC and a 6.3% increase in HDL-C, with non-significant trends towards lower LDL-C, VLDL-C, and TG. The treatment was found to induce a lesser atherogenic lipid profile, exhibiting cardio-protective properties. A similar study examined the corrective effect of M. oleifera dietary leaves on dyslipidemia in Type 2 diabetic patients (Kumari, 2010). Compared to the control group, the experimental group which received 8 g of M. oleifera leaf powder daily for 40 days experienced a significant fall in the plasma levels of TC (−14%), LDL-C (−29%), VLDL-C (−15%), and TG (−14%) whilst HDL-C levels increased by 9% but the HDL-C/non-HDL-C ratio increased by 37%.

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4.9. Antifertility activity Although there is an abundance of contraceptive drugs and devices available in the market today, adverse drug reactions and safety for their long-term use will always be a major concern. Medicinal plants have been used historically by women to aid in child delivery, stimulate menstrual flow or reduce fertility (Bodhankar et al., 1974). These herbal remedies provide an especially valuable alternative to modern contraceptive options for women in rural communities in developing countries who lack access to healthcare and cannot afford the cost of these medicines. Moreover, there is an increasing need to study and evaluate the potency of medicinal plants as it can generate greater confidence and acceptability of herbal contraceptives especially in developing countries. Moringa oleifera is widely regarded for its various medicinal properties and has been studied in scientific literature for its anti-fertility properties. Previous studies have reported on the antifertility activity of aqueous extracts of M. oleifera roots (Shukla et al., 1988) and leaves (Nath et al., 1992) in rats where a defect in implantation was induced. The antifertility effect of alcoholic extracts of M. oleifera stem bark in female albino rats was reported by Zade and Dabhadkar (2015). Pregnant rats were randomized into four groups and were given laparotomies on the 10th day of pregnancy; live fetuses were observed in both the horns of the uterus. Rats in the control group were orally administered with 0.5 ml of distilled water once daily while those in the experimental group were administered 25, 50 and 100 mg/kg doses of M. oleifera stem bark respectively. The effect of alcoholic extracts of M. oleifera on estrogenic activity and estrous cycle was observed to confirm the anti-fertility activity. The alcoholic extract was found to significantly reduce the number of live fetuses, whereas the resorption index and post implantation losses increased significantly. The percentage abortion was found to be highest with the 100 mg/kg dose. In ovariectomized immature young rats, the extract showed significant estrogenic effect (vaginal opening, vaginal cornification and increased uterine weight) and also extended the estrous cycle and particularly diestrous phase in the experimental animals. They attributed the disruption of the extracts on the ovary through ovarian and extra ovarian hormones (Zade and Dabhadkar, 2015). A recent study examined the antifertility potential of ethanol extracts of leaves of M. oleifera in female Wistar rats (Agrawal et al., 2018). The extracts, at concentrations of 100, 250 and 500 mg/kg were evaluated on fertility, implantation, decidualization and local cytokine signaling in female Wistar rats with artificially induced decidualization. Artificial decidualization was induced by intraluminal injections and female rats were ovariectomized. Three groups of rats (6 in each group) were administered 100, 250 and 500 mg/kg ethanol extract and control group female rats received 0.5% gum acacia for 5– 9 days. Moringa oleifera at doses of 250 and 500 mg/kg led to defective implantation when compared to the control group which could be due to defective decidualization. Further, artificial decidualization studies revealed a dose-dependent reduction in weight gain, estradiol levels and progesterone levels, which led to the reduced expression of various local cytokines, cyclooxygenase-2 (COX-II), leukemia inhibitory factor (LIF), vascular endothelial growth factor (VEGF) and IL-11. These cytokines and their receptors in the uterus are involved in various aspects of implantation. The analysis of uterine tissue progesterone and estrogen levels showed a dose-dependent reduction in the treated group compared to control group. Hence it was found that M. oleifera extracts induced anti-fertility activity by interfering with implantation and the decidualization process perhaps through its antioestrogenic and antiprogestogenic effect. They suggested that further investigations were necessary to determine its potential contraceptive actions and to identify the active constituent responsible for the anti-implantation activity.

Please cite this article as: B. Padayachee and H. Baijnath, An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.08.021

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4.10. Central nervous system (CNS) activity The central nervous system (CNS) is a vital organ system of the human body. Degenerative nerve diseases such as Alzheimer's disease affect many of the body's activities, such as balance, movement, memory, mental functioning and heart function. These diseases are incurable and often life threatening. Drugs acting on the central nervous system are among the most widely used group of pharmacological agents. The mechanisms by which various drugs act on the CNS have not always been clearly elucidated. Many medicinal plants have been reported to display activity against CNS disorders and act as very useful remedies for the alleviation of pain and discomfort. It has become increasingly important to identify medicines which have shown improved effectiveness and less adverse effects to treat these conditions. Since there is a paucity of information in the scientific literature on this subject, there is an emerging need to explore and review some of the wellcontrolled studies that have documented the various CNS activities displayed by M. oleifera. Skeletal muscle relaxants are used to treat both muscle spasms and spasticity. Current antispasmodic drugs such as cyclobenzaprine and antispasticity agents such as dantrolene are used with caution due to their many side effects and contra-indications and are also used warily in elderly patients, children and patients with heart conditions Bhattacharya et al. (2014). The locomotor activity and muscle relaxant activity of ethanolic extracts of M. oleifera in albino rat models was evaluated by Bhattacharya et al. (2014). The CNS depressant action was studied in the actophotometer test and muscle relaxant activity by the rotarod test. The albino rats were divided into six groups of six rats each. The control group was administered normal saline solution orally (2 ml/kg), another group was given the standard drug Diazepam (10 mg/kg) and the experimental groups were given the extracts at doses of 50, 100, 200 and 400 mg/kg respectively. Results showed that ethanolic extracts of M. oleifera exhibited significant CNS depressant and muscle relaxant activity in a dose-dependent manner. They suggested that compounds present in the plant such as flavonoids and saponins, which can easily cross the blood–brain barrier and exert various effects on the CNS, like memory, cognition and neurodegeneration or, have an agonistic action on the gamma-aminobutyric (GABA) acid receptor complex, may be responsible for its CNS depressant and muscle relaxant activity. Bakre et al. (2013) examined the neuro-behavioral and anticonvulsant properties of the ethanol extract from the leaves of M. oleifera in mice. Neuro-behavioral properties were evaluated using the open field, hole board, Y-maze, elevated plus maze (EPM) and pentobarbitone-induced hypnosis. Pentylenetetrazol, picrotoxin and strychnine induced convulsion tests were used to investigate the anticonvulsive actions of M. oleifera. The result showed that the extract (250–2000 mg/kg) caused a significant dose-dependent decrease in rearing, grooming, head dips and locomotion. It also enhanced learning and memory and increased the anxiogenic effect. In addition, the extract (2000 mg/kg) protected mice against pentylenetetrazol induced convulsion, but had no effect on picrotoxin- and strychnine-induced convulsion. The effects of the extract in the various models were comparable to those of the standard drugs used. The authors concluded that the leaves possessed a CNS depressant and anticonvulsant properties, the action of which was possibly mediated through the enhancement of the central inhibitory mechanism involving the release of GABA acid. Ganguly and Guha (2008) determined the effects of chronic oral treatment of ethanolic extract of M. oleifera leaves on levels of brain monoamines (norepinephrine, dopamine and serotonin) in a rat model of Alzheimer's disease (AD). AD was induced in rats by intracerebroventricular (ICV) infusion of colchicine. Control rats were treated with saline (5 ml/kg) and experimental group rats were treated with M. oleifera leaf extract at doses of 50, 100, 150, 200, 250, 300 and 350 mg/kg respectively 14 days. In the first set of experiments, the effective dose of M. oleifera was standardized on rats by observing their performance in radial arm maze (RAM) task. Treatment with the extract

markedly increased the number of correct choices in a RAM task with variable alteration of brain monoamines and also helped to improve memory. Treatment with M. oleifera also showed an increase in beta wave frequency together with a significant decrease in the number of spike discharge suggesting a role in improving co-ordination and brain functioning. The authors suggested that M. oleifera may have a protective action on dopaminergic neurons in the cortical and hippocampal region and thus may support the memory process. Based on their research, Ganguly and Guha (2008) concluded that M. oleifera aids in providing some protection against Alzheimer's disease in rat models by causing an alteration in brain electrical activity and altering monoamine levels in discrete brain regions. Moringa oleifera has been used traditionally to treat migraines and has also been studied for this potential in scientific literature. Many theories have been established for understanding the mechanism of migraines, of these, one of the theories suggests the involvement of the serotonergic and dopaminergic systems. Upadhye et al. (2012) explored the antimigraine potential of alcoholic fractions of the leaf juice of M. oleifera in three animal models: Apomorphine-induced climbing behavior; l-5HTP-induced syndrome and MK 801-induced hyperactivity. It was found that the leaf juice significantly reduced all behavioral activity in a dose-dependent manner, which could be attributed to its action on dopaminergic and serotonergic receptors. It was concluded that M. oleifera may be effectively used in the treatment or management of migraines. Continuous stress or CNS neurochemical imbalances results in a constant state of depression. Oxidative stress (OS) is considered to be a major factor in causing psychiatric diseases such as anxiety and depression, and these CNS disorders appear to result from the imbalance in oxidation–reduction reactions. The leaves of M. oleifera have shown to possess significant antioxidant and anti-inflammatory properties, and have the potential to treat depression caused by OS or inflammation (Kaur et al., 2015). The acute and chronic behavioral and antidepressant effects of alcoholic extracts of M. oleifera leaves (MOE) were evaluated in standardized mouse models of depression (Kaur et al., 2015). Combination effects of MOE with the standard antidepressant drug fluoxetine were also assessed. Mice were exposed to the tail suspension test (TST), forced swim test (FST) and the locomotor activity test to induce depression. A significant increase in the locomotor activity was displayed by MOE-treated animals when compared to the vehicle controls as well as, a more pronounced increase in animals administered with a combination of MOE (200 mg/kg) and fluoxetine (10 mg/kg), suggesting an additive interaction between these two agents. This was attributed to its influence on noradrenergic and serotonergic transmission pathways which can induce antidepressant activity. They concluded that the combination MOE with low doses of fluoxetine or other SSRI drugs have a promising potential for the development of alternative therapies for treating depression (Kaur et al., 2015). 4.11. Antiasthmatic activity Asthma is a chronic respiratory disorder that affects a large proportion of populations throughout the world accounting for approximately 90% of cases in most surveys worldwide (Mahajan et al., 2009). Complementary and alternative medicine has been used to treat asthma for hundreds of years. The Ayurvedic system of medicine has gained greater recognition in this regard and many of the drugs from indigenous plant sources have been recommended for the treatment of bronchial asthma and have been largely successful in controlling the disease as well. Moringa oleifera in particular has been useful in the treatment of asthma. Mahajan et al. (2009) examined the effectiveness of n-butanol extracts of the seeds of M. oleifera (MONB) against ovalbumin-induced airway inflammation in guinea pigs. Their results indicated that MONB treatments showed protective effects against acetocholine-induced bronchoconstriction and airway inflammation by improving tidal volume and increasing respiration rate and total and differential cell counts

Please cite this article as: B. Padayachee and H. Baijnath, An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.08.021

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in blood and bronchoalveolar lavage fluid. They concluded that the antiasthmatic activities exhibited by MONB occurred through the modulation of Th1/Th2 cytokine imbalances (Mahajan et al., 2009). Agrawal and Mehta (2008) conducted a clinical study to investigate the efficacy of seed kernels of M. oleifera in the treatment of bronchial asthma. The dried seed kernels at a dose of 3 kg were administered to 20 patients with mild to moderate asthma for 3 weeks. The results showed that there was a marked decrease in the severity of symptoms of asthma and a simultaneous improvement in lung function parameters upon treatment with M. oleifera extracts. The majority of patients presented with a significant increase in hemoglobin (Hb) values and a decrease in erythrocyte sedimentation rate (ESR). There was also significant improvement in forced vital capacity, forced expiratory volume and peak expiratory flow rate values in asthmatic patients. None of the patients showed any unfavorable effects with M. oleifera. Hence, the seeds of M. oleifera were considered to be useful for treatment of patients with bronchial asthma (Agrawal and Mehta, 2008). 5. Conclusion Moringa oleifera is an impressive and outstanding tree due to its exceptional value, from a nutritional as well a therapeutic point of view. It has remarkable potential in providing an inexpensive and credible alternative to not only good nutrition, but also a positive contribution to health due to the vast medicinal properties that it offers. Although M. oleifera has been thoroughly investigated and utilized for its medicinal value, further studies are still required to explore its therapeutic and other possible benefits, and to also address many of the challenges that still remain with respect to scientific scrutiny of its medicinal uses. The multitude of pharmacological and phytochemical activities and traditional medicinal uses that M. oleifera possesses need to be analyzed more rigorously and comprehensively so that sound scientific inspection on the effectiveness of the documented literature can be further justified. Additional research is needed in this regard and furthermore, clinical trials should be performed to evaluate the adverse effects or toxicity of M. oleifera in human beings so that it can be used safely. The therapeutic potential of this miracle tree needs to be further discovered and critically evaluated so that the full benefits can be utilized and that communities in need can capitalize on its extraordinary value. Declaration of Competing Interest None. Acknowledgements The authors wish to thank the National Research Foundation (NRF), South Africa for their internship programme in 2012 as well as the University of Kwa-Zulu Natal (UKZN) for providing us with the facilities to carry out this research. References Agrawal, B., Mehta, A., 2008. Anti-asthmatic activity of Moringa oleifera Lam: a clinical study. Ind. J. Pharmacol. 40, 28–31. Agrawal, S.S., Vishal, D., Sumeet, G., Shekhar, C., Ashish, N., Parul, D., Ankita, S., Prakash, A., Prakash, T., Kumar, P., Varun, S., 2018. Antifertility activity of ethanol leaf extract of Moringa oleifera Lam in female wistar rats. Indian J. Pharm. Sci. 80, 565–570. Akhtar, A.H., Ahmad, K.U., 1995. Anti-ulcerogenic evaluation of the methanolic extracts of some indigenous medicinal plants of Pakistan in aspirin-ulcerated rats. J. Ethnopharmacol. 46, 1–6. Al Asmari, A.K., Albalawi, S.M., Athar, T., Khan, A.Q., Al-Shahrani, H., Islam, M., 2015. Moringa oleifera as an anti-cancer agent against breast and colorectal cancer cell lines. PLoS One 10, 1–14. Alhakmani, F., Kumar, S., Khan, S.A., 2013. Estimation of total phenolic content, in-vitro anti-oxidant and anti-inflammatory activity of flowers of Moringa oleifera. Asian Pac. J. Trop. Biomed. 3, 623–627. Al-Malki, A.L., El Rabey, H.A., 2015. The antidiabetic effect of low doses of Moringa oleifera Lam. seeds on streptozotocin induced diabetes and diabetic nephropathy in male rats. Biomed. Res. Int. 2015, 1–13.

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Aney, J.S., Tambe, R., Kulkarni, M., Bhise, K., 2009. Pharmacological and pharmaceutical potential of Moringa oleifera: a review. J. Pharm. Res. 2, 1424–1426. Anudeep, S., Prasanna, V.K., Adya, S.M., Radha, C., 2016. Characterization of soluble dietary fiber from Moringa oleifera seeds and its immunomodulatory effects. Int. J. Biol. Macromol. 91, 656–662. Anwar, F., Bhanger, M.I., 2003. Analytical characterization of Moringa oleifera seeds, part-I. The antibiotic compound and its deactivation in aqueous solution. Phillip. J. Sci. 51, 6558–6563. Anwar, F., Latif, S., Ashraf, M., Gilani, A.H., 2007. Moringa oleifera: a food plant with multiple medicinal uses. Phytother. Res. 21, 17–25. Araújo, L.C.C., Aguiar, J.S., Napoleão, T.H., Mota, F.V.B., Barros, A.L.S., Moura, M.C., Coriolano, M.C., Coelho, L.C.B.B., Silva, T.G., Paiv, P.M.G., 2013. Evaluation of cytotoxic and anti-inflammatory activities of extracts and lectins from Moringa oleifera seeds. PLoS One 8, e81973. Asres, K., 1995. 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Please cite this article as: B. Padayachee and H. Baijnath, An updated comprehensive review of the medicinal, phytochemical and pharmacological properties of Moringa oleifera..., South African Journal of Botany, https://doi.org/10.1016/j.sajb.2019.08.021