In vitro and in vivo antioxidant potentials of Alchornea floribunda leaf extract, fractions and isolated bioactive compounds

Objective: Alchornea floribunda leaves are widely used in ethnomedicine for the management of immuno-inflammatory disorders. We investigated the in vivo and in vitro antioxidant activity of the leaf extract, fractions and isolated compounds of A. floribunda. Materials and Methods: The ethyl acetate fraction of the methanol leaf extract was subjected to several chromatographic separations to isolate compounds 1-4. The structures of the isolated compounds were elucidated by a combination of 1D and 2D NMR and mass spectrometry. Oxidative stress was induced with carbon tetrachloride (CCl4). Further analysis on the isolated phenolic compounds were done using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and hydrogen peroxide scavenging activity tests. Results: The ethyl acetate fraction at 200 mg/kg produced significant (p<0.05) elevations of catalase enzyme activity and a significant (p<0.05) reduction in serum malondialdehyde. The chemical investigation of the ethyl acetate fraction led to the isolation of three flavans, (-) cathechin (1), (-) epicathechin (2), (+) epicathechin (3) and a flavanone, 2R, 3R dihydroquercitin (4). In hydrogen peroxide scavenging assay, (-) epicathechin exhibited an EC50 value of 8 μg/ml, similar to the standard ascorbic acid (EC50 = 8 μg/ml). (-) epicathechin showed scavenging of DPPH radical with EC50 value of 19 μg/ml while in the FRAP assay, it had EC50 value of 46 μg/ml which was lower than that of the standard, ascobic acid (EC50 = 66 μg/ml). Conclusion: The medicinal uses of A. floribunda may be due to the antioxidant activities of its phenolic compounds. Keywords