Abstract

The study aimed to identify the chemical constituents of Leucaeana leucocephala leaves and evaluate the antioxidant and antimicrobial activities of the extract and compounds. An acylated flavanol glycoside, quercetin -3-O-(2''-trans-p-coumaryl)-α-rhamnopyranosyl-(1'''→6'')-β-glucopyranoside (1) in addition to quercetin-3-O-α –rhamnopyranosyl-(1'''→2'')-β–glucopyranoside(2), quercetin-7-O-α–rhamnopyranosyl-(1'''→2'')-β–glucopyranoside(3),quercetin-3-O-α- rhamnopyranoside(4), quercetin-3-O-β–glucopyranoside(5) vitexin(6) isovitexin (7) and quercetin(8) were isolated for the first time from the Leucaeana leucocephala. The antioxidant activity of the extract and the isolated compounds 1, 3 & 4 were evaluated by Reducing Power, FRAP, DPPH, Metal chelating and ABTS assays. Compound (3) recorded the highest antioxidant activity in comparison with the extract and other compounds. The extract and compound 1, 2, 3 and 5 were studied for their antimicrobial activity. Both the extract and compound 1 have significant activity against gm-ve bacteria, moderate to gm +ve and Candida and inactive towards fungi. The structures of compounds were elucidated on the basis of spectral analysis. L. leucocephala possess good antioxidant, antibacterial properties and could serve as free radical inhibitors or scavengers, acting possibly as primary antioxidants and have to be investigated for anti-inflammatory and anticancer activities.

Key words: Leucaeana leucocephala, acylated flavonol glycoside, antioxidant activity, DPPH, ABTS, FRAP, antimicrobial