Cytotoxicity Study Of Antioxidant Flavonoids From Bauhinia Tomentosa Leaf Extract

A 1, 1-diphenyl-2-picrylhydrazyl (DPPH) activity-guided fractionation procedure was used to isolate the antioxidant constituents of a 50% ethanol dried leaf extract of Bauhinia tomentosa. Four flavonol glycosides: kaempferol-7-O-rhamnoside (1), kaempferol-3-O-glucoside (2), quercetin-3-O-glucoside (3) and quercetin-3-Orutinoside (4) were isolated by accelerated gradient chromatography (AGC) and Sephadex LH-20 column chromatography. Compounds 1-3 are reported for the first time from this species. The structures of the compounds were established by spectroscopic methods (1H NMR, 13C NMR and MS). A DPPH spectrophotometric assay was employed to evaluate the antioxidant activity of the isolated compounds. Compound 3 had higher antioxidant activity than L-ascorbic acid while 1 and 4 similarand 2 lower activities. Compounds 2-4 were non-cytotoxic, but kaempferol-7-O-rhamnoside (compound 1) displayed slight cytotoxicity to bovine dermal cells (LC50 = 116.58 μg/ml) in the tetrazolium (MTT) based assa