Abstract

Naturally nutritive and non-nutritive occurring antioxidants have been proven potent and safe for management of variety of diseases. This study investigated the antioxidant and free radical scavenging capacity of crude and refined Azadirachta indica (Neem tree) oil. The neem crude oil (NCO) was extracted from the seeds by mechanical press and degummed. The neem oil was de-pigmented with activated charcoal, and fractionated with silica gel in a capillary column. The ability of the oils to act as hydrogen/electrons donor were determined in-vitro using 2, 2-dipphenyl-1-picrylhydrazyl (DPPH), 2, 2-azinobis - (3-ethylbenzothiazolin - 6-sulfonic acid) diammonium salt (ABTS), lipid peroxyl (LP) and nitric oxide (NO) radicals scavenging assays, at different extract concentrations (0.1, 0.2, 0.3 and 0.4 mg/mL). The IC₅₀ of the NCO oil (1.50 ± 0.10 mg/mL) showed that antioxidant activity is comparable to vitamin C and beta-carotene (1.60 ± 0.10 and 1.27 ± 0.12 mg/mL respectively) in scavenging DPPH radical. The crude neem oil exhibited superior activity against NO radical, than the refined oil and vitamin C. Generally, in the four antioxidant assays, a significant correlation existed between concentrations of the oils and percentage inhibition of the four different radicals. GC/MS analyses identified monounsaturated and saturated fatty acids, aldehydes and pentanethiol as the major compounds in the oils, these may account for their antioxidant capacity.

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