Comparative <i>in-vitro</i> antioxidant studies of crude methanol extract and four solvent fractions of red cultivar <i>Allium cepa</i> l. bulbs

Oxidative stress-induced disease conditions are on the increase and there is need for natural sources of antioxidant for relieving stress. The crude extract of Allium cepa L. has been well published as a potential natural source of antioxidant. But there is inadequate information on the antioxidant activities of fractionated extracts of the plant. The in-vitro antioxidant capacity of crude extract of red cultivar A. cepa bulbs and its four solvent fractions were studied and compared using Nitric oxide radical inhibitory assay (NORIA), FRAP and DPPH antioxidant models. The results of the three models revealed that the crude methanol extract exhibited very good antioxidant activities. However, with the aid of DPPH, the crude methanol extract, ethyl acetate and methanol fractions exhibited excellent antioxidant activities in comparison with ascorbic acid. Serial extraction did not make any of the fractionated extracts better than the crude extract of the red cultivar A. cepa bulbs. These results also showed that red cultivar A. cepa bulbs is a natural source of antioxidants and could serve as therapeutic agent in the prevention or slowing down of oxidative stress. Further studies are currently underway to identify the active component responsible for the observed antioxidant properties.