Cytotoxicity and Structure-Activity Relationships of Xanthone Derivatives from Mesua beccariana, Mesua ferrea and Mesua congestiflora towards Nine Human Cancer Cell Lines

The cytotoxic structure-activity relationships among a series of xanthone derivatives from Mesua beccariana, Mesua ferrea and Mesua congestiflora were studied. Eleven xanthone derivatives identified as mesuarianone ( 1), mesuasinone ( 2), mesuaferrin A ( 3), mesuaferrin B ( 4), mesuaferrin C ( 5), 6-deoxyjacareubin ( 6), caloxanthone C ( 7), macluraxanthone ( 8), 1,5-dihydroxyxanthone ( 9), tovopyrifolin C ( 10) and α-mangostin ( 11) were isolated from the three Mesua species. The human cancer cell lines tested were Raji, SNU-1, K562, LS-174T, SK-MEL-28, IMR-32, HeLa, Hep G2 and NCI-H23. Mesuaferrin A ( 3), macluraxanthone ( 8) and α-mangostin ( 11) showed strong cytotoxicities as they possess significant inhibitory effects against all the cell lines. The structure-activity relationship (SAR) study revealed that the diprenyl, dipyrano and prenylated pyrano substituent groups of the xanthone derivatives contributed towards the cytotoxicities.