Background M. aboensis has wide ethnopharmacological applications but very little has been done on the pharmacological basis for these indications. This study evaluated the antioxidant potentials of the leaf extracts of M. aboensis. Methods Total phenolic content of the extract and fractions was carried out using folin-ciocalteu method while in vivo site specific effect determined using carbon tetrachloride (CCl4)-induced liver oxidative damage. Chromatographic separations of the most active fraction led to the isolation of compounds 1 and 2 with their structures elucidated by a combination of 1D and 2D NMR and mass spectrometry. Inhibition of liver microsome lipid peroxidation was used to evaluate the antioxidant activities of these compounds while DPPH test was used to study their interaction. Results Ethyl acetate fraction had the highest phenolic content of 305.2 mgGAE/g with n-hexane fraction having the least (26.1 mgGAE/g). Structural elucidation revealed compound 1 as epicathechin-(2β→O→7, 4β→8)-cathechin and compound 2 as epicathechin-(2β→O→7, 4β→8)-epicathechin. Compounds 1 & 2 inhibited liver microsome lipid peroxidation with EC50 of 46 and 55 µg/mL respectively. Combination of the compounds produced synergic inhibition of DPPH radical with EC50 of 7 µg/mL against 9 µg/mL produced by ascorbic acid. Conclusion M. aboensis expressed strong antioxidant property which may explain its diverse ethnopharmacological uses.
Keywords: Millettia aboensis; free radicals; lipid peroxidation; oxidative stress; procyanidines.