Isolation, Structure Elucidation and Antioxidant Screening of Secondary Metabolites from Rhynchosia pseudo-cajan

The phytochemical investigations on the chloroform and ethyl acetate soluble fractions of Rhynchosia pseudo-cajan Cambess. led to the isolation of eighteen compounds, namely; octadecane (1), triacontyl palmitate (2), heptatriacontyl benzoate (3), 1-hentriacontanol (4), 1-heptatriacontanol (5), 14,20-dimethyl-1-heptacosanol (6), icosyl-p-hydroxy benzoate (7), beta-sitosterol (8), stigmasterol (9), beta-amyrin (10), mupinensisone (11), alpinetin (12), and pinostrobin (13), 3-oxoleane-9(11), 12-diene-30-oic acid (14), 4',5,6-trihydroxy-7-methoxy-flavone (15), 2',4',5,7-tetrahydroxyisoflavone (16), beta-sitosterol glucoside (17) and naringin (18). Their structures were established by using UV, IR, mass (EI-MS, HR-EI-MS, FAB-MS, HR-FAB-MS), 1D NMR (H-1, C-13) and 2D NMR (HMQC, HMBC, COSY) and by comparison with the published data of the related compounds. Among these isolates (1-18), the compounds 2, 8, 9, 10 and 17 are known from this source while all others have been isolated for the first time from this source. All the isolates were screened for their antioxidant potential. The results revealed that the compounds 7, 12, 13, 15 and 16 exhibited significant antioxidant potential.