Medicinal uses of Neem tree
Neem is a fast-growing evergreen tree used in treatment of multiple diseases for more than 4000 years. It is one of the two species in the genus Azadirachta and is native to the Indian subcontinent i.e. India, Nepal, Pakistan, Bangladesh, Srilanka and the Maldives. It typically grows in tropical and semitropical regions. The tree also grows in islands located in the southern part of Iran and is indigenous to Southeast Asia and West Africa. Neem has been recently introduced in the Caribbean and several Central American countries including Mexico.
Neem was described by De Jussieuin 1830 and its taxonomic classification is as follows:
- Kingdom: Plantae
- Division: Magnoliophyta
- Class: Magnoliopsida
- Subclass: Rosidae
- Order: Sapindales
- Family: Meliaceae
- Genus: Azadirachta
- Species: Azadirachta indica
Component of the Neem Tree
To know the components of the Neem tree, a mixture of free fatty acids was analyzed by gas chromatography of the fatty acids. The latter showed that it contained nine fatty acids. The most abundant are 43.1% of Δ1-oleic acid, 19.4% of palmitic acid, 17.6% of Δ2linoleic acid, 16.4% of stearic acid, and 0.3% of arachidic acid; minor fatty acids include 0.6% of odeolidic acid, 0.3% of Δ3–α-linoleic acid, 0.2% of margaric acid, 0.2% of behenic acid, 0.2% of lignoceric acid, and 0.1% of Δ1–gadoleic acid (Gossé et al., 2005).
Azadirachtin, a complex tetranortriterpenoid limonoid from the Neem seed, is the main component responsible for both antifeedant and toxic effects in insects. Another limonoid and sulfur-containing compound with repellent, antiseptic, contraceptive, antipyretic, and antiparasitic properties are found elsewhere in the tree, e.g., leaves, flowers, bark, and roots (Mordue and Nisbet 2000). Limonoids, also denominated tetranortriterpenoids, are a group of highly oxygenated, heterocyclic compounds with alkoxy and hydroxyl groups, of which azadirachtin is the most well- known (Ospina-Salazár et al., 2015)
Neem has been found to be effective in treatment of malaria, tuberculosis, rheumatism, arthritis, jaundice, parasitic diseases as well as skin diseases. The extracts of various plant parts have also been found to be beneficial in cardiovascular diseases, hepatitis, fungal infection, psoriasis, eczema, lice, fungal infections and ulcers. Neem is also used in cosmetic products for treatment of acne and pimples and improving skin elasticity. Given below is a short discussion of the various therapeutic properties found in neem.
Activity of the bark, leaf, seed and fruit extracts of neem has been evaluated against bacteria isolated from oral cavity. Results have revealed that bark and leaf extracts possess activity against all the tested bacteria. Seed and fruit extracts have shown activity at higher concentrations only. Neem bark extract (NBE) has also been found to significantly block HSV-1 entry into cells at concentrations ranging from 50-100 mg/mL. Neem has also shown potential to be used in wound dressings.
Methanolic extract of neem leaves has shown virucidal activity against coxsackievirus virus B-4. The antiviral activity of neem leaves has been found to be due to the presence of flavonoids, triterpenoids and their glycosides. The minimal inhibitory concentrations (8000µg/mL) of the leaves extract has been found to have no toxicity against Vero (African green monkey kidney) cells
Antimalarial activity of neem leaf and stem bark extracts has been evaluated against Plasmodium berghei infected albino mice. The leaf and stem bark extracts have shown efficacy in reducing the level of parasitemia in infected mice to about 51-80% and 5687%, respectively. The effect of methanolic extracts of seed kernels of ripe and unripe fruits of neem have also been studied on early erythrocytic schizogony of P. berghei
NS2B-NS3 protease (NS2B-NS3 pro) of dengue virus (DENV) is the prime therapeutic target for the development of anti-dengue drugs to combat the DENV infection, which is currently an increasing health problem in many countries. An in silico study has reported the inhibitory potential of neem and its triterpenoids constituents viz. nimbin, desacetylnimbin, desacetylsalannin, azadirachtin and salannin against DENV NS2B-NS3 pro using molecular docking.
The in vitro antifungal activity of neem leaves and seed kernel have been evaluated against Monilinia fructicola, Penicillium expansum, Trichothecium roseum and Alternaria.The aqueous, ethanolic and ethyl acetate extracts of neem leaves have also shown significant activity against Aspergillus flavus, A. fumigatus, A. niger, A. terreus, Candida albicans and Microsporum gypseum. Ethyl acetate extract has shown the strongest antifungal activity and its HPLC analysis revealed the presence of nimonol. A recent study has shown that addition of neem powder to acrylic resin denture base materials reduces the adhesion of C. albicans which prevents denture stomatitis
A combination of the entomopathogenic fungus Metarhizium anisopliae with neem oil has been found to effectively increase the half-life and virulence of the fungus when tested against Aedes aegypti larvae, even under simulated field conditions. Neem oil has also been found to display a protective activity towards M. anisopliae from the damaging effects of ultraviolet radiation.
Neem has also been used in the treatment of peptic ulcers. Aqueous extract of neem leaves has been found to display a significant antiulcerative activity on Wistar rats at a dose of 600mg/kg. The effect of neem has also been evaluated against peptic ulcers in albino mice. The mechanism of antiulcer activity of neem leaves extract has also been determined.
The ethanolic extract of neem root bark has also been evaluated for antidiabetic activity. The neem root bark extract (NRE) showed statistically significant results at 800 mg/kg dose in an oral glucose tolerance test (OGTT). Neem extract at a dose of 250 mg/kg (single dose study) significantly reduced glucose levels (18%) in treated diabetic rats versus the control group as well as reduced cholesterol (15%), triglycerides (32%), urea (13%), creatinine (23%) and lipids (15%). Multiple doses administered over a 15 day period have also been shown to significantly lower the above blood parameters in the treated group. Azadirachtin, the active component of neem has also been found to display a protective action against pancreatic β-cells
A study has reported that a 4% infusion of neem leaves in fresh drinking water acts as a natural growth promoter and an immuno-stimulant in chickens contributing to an improved body weight gain, FCR feed conversion ratio, gross return, lower mortality and higher antibody titer against infectious bursal disease (IBD). Aqueous extract of neem has also been found to augment both specific (humoral and cell-mediated immunity) and nonspecific immune responses
Neem seed oil has been found to possess a powerful spermicidal as well as spermatogenesis inhibitory property. It has also been found to reduce sperm motility and count. Neem seed oil which is used as a powerful spermicidal and significantly inhibit spermatogenesis. It inhibits sperm motility and count and cessation of fertility. Neem also has antiimplantation and abortifacients properties. It has been found that spermatozoa of human and Rhesus monkeys die within 30 min of contact with neem seed oil using an intra vaginal dose of 1 mL
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Ospina-Salazár, D. I., Hoyos-Sánchez R. A., Orozco-Sánchez, F., Arango-Arteaga, M. and Gómez-Londoño, L. F. (2015). Antifungal activity of Neem (Azadirachta indica: Meliaceae) extracts against dermatophytes. Acta Biol. Colomb. 20(3): 201-207.
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