This study evaluated the in vitro antioxidant activity of water (VAWE) and ethanol (VAEE) extracts of the leaf of Vernonia amygdalina. The antioxidant activity of each extract was evaluated using various radicals or oxidation systems. The total phenolic or flavonoid contents and their correlation with total antioxidant activity were also evaluated. VAEE exhibited antioxidant scavenging potential comparable to butylated hydroxyanisole (BHA), but higher than butylated hydroxytoluene (BHT) or VAWE. The total antioxidant scavenging activity of the extracts measured as the millimolar (mM) equivalent of vitamin C gave VAEE a 10.09 ± 1.63, which is comparable to BHA with a 9.31 ± 1.17, but higher than VAWE with an 8.75 ± 1.28 or BHT with a 6.14 ± 2.01. Extracts inhibited bleaching of B-carotene, oxidation of linoleic acid and lipid peroxidation induced by Fe2+/ascorbate in a rat liver microsomal preparation. The total flavonoid and phenolic contents correlated positively with total antioxidant activity. The total flavonoid content also correlated well with total phenolic. Extracts of V. amygdalina contain natural antioxidants, have the potential to act as antioxidants against aqueous radicals and reactive species ions. The total phenolic content of the extracts is related to its total flavonoid, and it may be responsible for its total antioxidant activity.
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