C-Glycosylated flavonoids from black gram husk: Protection against DNA and erythrocytes from oxidative damage and their cytotoxic effect on HeLa cells.

C-Glycosyl flavones are present in different plant tissues and they exhibit health benefits. In the present study, it was found that C-glycosyl flavones are distributed in different milled fractions of black gram and among these fractions, husk had the highest content of C-glycosyl flavones. Two C-glycosyl flavones from black gram husk were extracted and purified by preparative high-performance liquid chromatography (HPLC) column. The purity of each compound was assessed by analytical C18 column. The structure of each compound was confirmed by LC-MS/MS, NMR. The molecular mass of these compounds were found to be [M-H]-, m/z 431.36 and [M-H]-, m/z 431.35 and were identified as vitexin and isovitexin, respectively. Content of vitexin and isovitexin in aqueous ethanol extract was found to be 76 and 65 mg/g of extract, respectively. These C-glycosyl flavones protected DNA and erythrocytes from oxidative damage. The IC50 values for vitexin, isovitexin and quercetin for hemolysis were 6, 5.7 and 2.37 μg, respectively. These compounds also triggered the process of apoptosis in HeLa cells by downregulating Bcl-2 level with the simultaneous upregulation of Bax and caspase-3 protein expression. Thus, C-glycosyl flavones from black gram husk protected DNA and erythrocytes from oxidative damage and exhibited anticancer activity.