A new DNA-intercalative cytotoxic allylic xanthone from Swertia corymbosa.

Phytochemical investigation of the CHCl3 fraction of Swertia corymbosa resulted in the isolation of a new 3-allyl-2,8-dihydroxy-1,6-dimethoxy-9H-xanthen-9-one (1), along with four known xanthones, gentiacaulein (3), norswertianin (4), 1,3,6,8-tetrahydroxyxanthone (5), and 1,3-dihydroxyxanthone (6). Structure of compound 1 was elucidated with the aid of IR, UV, NMR, and MS data, and chemical transformation via new allyloxy xanthone derivative (2). Compounds 1-6 exhibited various levels of antioxidant and anti-α-glucosidase activities. Absorption and fluorescence spectroscopic studies on 1-6 indicated that these compounds could interact with calf thymus DNA (CT-DNA) through intercalation and with bovine serum albumin (BSA) in a static quenching process. Compound 1 was found to be significantly cytotoxic against human cancer cell lines HeLa, HCT116, and AGS, and weakly active against normal NIH 3T3 cell line.