Garcixanthones B and C, new xanthones from the pericarps of Garcinia mangostana and their cytotoxic activity

Two new prenylated xanthones, garcixanthones B (1) and C (2) and six known metabolites: gartanin (3), 1,3,8- trihydroxy-2-(3-methyl-2-butenyl)-4-(3-hydroxy-3-methylbutanoyl)-xanthone (4), rubraxanthone (5), 1,3,6,7-tetrahydroxy-8-prenylxanthone (6), garcinone C (7), and xanthone I (9-hydroxycalabaxanthone) (8) were separated from the EtOAc-soluble fraction of the air-dried pericarps of Garcinia mangostana (Clusiaceae). Their structures were verified on the basis of spectroscopic data analysis as well as by comparison with the literature. The cytotoxic activity of the new compounds was assessed against MCF7, A549, and HCT116 cell lines using sulforhodamine B (SRB) assay. Compounds 1 and 2 showed significant cytotoxic potential against MCF7 (human breast adenocarcinoma) and A549 (lung carcinoma) cell lines with IC(50)s 4.27 and 2.65 and 3.08 and 3.91 mu M, respectively compared to doxorubicin (0.06 and 0.44 mu M, respectively). However, they exhibited moderate activity towards HCT116 (colon carcinoma) cell line.