ISOLATION OF DIHYDROQUERCETIN GLYCOSIDE FROM THE ROOT BARK OF CALOTROPIS PROCERA AND ANTIOXIDANT AND CYTOTOXIC SCREENING OF THE CRUDE EXTRACTS.

The root bark of Calotropis procera (Family: Asclepiadaceae) was extracted with methanol. The methanolic extract was separated into hexane, chloroform, ethyl acetate, and water soluble fractions. The ethyl acetate fraction was subjected to bioassay-guided fractionation and final purification was achieved by column chromatography. The structure of the compound was elucidated by spectroscopic methods (ESI-MS, 1H and C NMR, COSY, HSQC, and HMBC) and the comparison of the data obtained with that reported in the literature. It was concluded that the compounds isolated was taxifolin 4’-O-β-D-glucopyranoside, a dihydroquercetin glycoside. The crude extracts of hexane, chloroform, ethylacetate, and water soluble fractions of methanol extract and the isolated compound were subjected to antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and brine shrimp lethality bioassay. The result shows that the maximum inhibitions in the DPPH assays were isolated compound (51.7 %), methanol (80.7 %), and water (29.2 %) fractions while ascorbic acid standard was (84.4 %). However, the results for hexane, chloroform and ethyl acetate fractions in the DPPH assays were poor and hence discarded. The results for the in vitro cytotoxicity activity shows that ethyl acetate and hexane fractions showed significant cytotoxicity with LC50 value of 1.0±0.2 and 2.4 ±0.1 respectively.