Isolation, structure elucidation and antioxidant screening of some natural products from Colebrookia oppositifolia

The phytochemical investigation on the chloroform and ethyl acetate soluble fractions of Colebrookia oppositifolia Smith. led to the isolation of four new-source compounds namely 1pentacosanol (1), stigmast-7-ene-3β-ol (2), p-hydroxybenzoic acid (3), ursolic acid (4) and seven known compounds namely triacontane (5), triacontanol (6), betulonic acid (7), negletein (8), 5,2′,6′-trihydroxy-7-methoxy flavone (9), quercetin (10) and 5,7,2′-trihydroxyflavone-2′-O-β-Dglucopyranoside (11). Their structures were established by using UV, IR, mass (EIMS, HREIMS, FABMS, HRFABMS), 1D NMR ( 1 H, 13 C) and 2D NMR (HMQC, HMBC, COSY) and by comparison with the published data of the related compounds. All the isolates (1-11) were studied for their antioxidant potential. Among these p-hydroxybenzoic acid (3), negletein (8), 5,2′,6′trihydroxy-7-methoxy flavone (9), quercetin (10) and 5,7,2′-trihydroxyflavone-2′-O-β-Dglucopyranoside (11) showed good antioxidant potential when compared with the BHT (butylated hydroxyl toluene, reference standard antioxidant)/blank..