Cytotoxic activities of xanthochymol and isoxanthochymol substantiated by LC-MS/MS

The methanol extract of the fruit rinds of Garcinia indica showed potent cytotoxic activity against three human cancer cell lines, colon (COLO-320-DM), breast (MCF-7) and liver (WRL-68), as determined by the MTT assay. Fractionation of the methanol extract into hexane-, chloroform- and ethyl acetate-soluble fractions and evaluation of cytotoxic activity of each of the fractions revealed that the ethyl acetate fraction was the most effective as compared to the two other fractions. Two polyisoprenylated benzophenones, xanthochymol and isoxanthochymol, were isolated from the ethyl acetate fraction. Both xanthochymol and isoxanthochymol as a single pure entity did not turn out to be as effective as the ethyl acetate extract from which they have been isolated. The concentrations of xanthochymol and isoxanthochymol in four different extracts--methanol, hexane, chloroform and ethyl acetate--were determined with the help of LC-MS/MS. On the basis of the LC-MS/MS data, combinations of xanthochymol and isoxanthochymol in different ratios were tested in the MTT assay and were found to be effective. Moreover, it was established from the LC-MS/MS data that the combination of xanthochymol and isoxanthochymol in a ratio of 1 : 2 showed maximal cytotoxicity.