<p>A new prenylated xanthone, mangostanaxanthone VIII (<b>7</b>) and six known metabolites: gartanin (<b>1</b>), 1,3,8-trihydroxy-2-(3-methyl-2-butenyl)-4-(3-hydroxy-3-methylbutanoyl)-xanthone (<b>2</b>), rubraxanthone (<b>3</b>), 1,3,6,7-tetrahydroxy-8-prenylxanthone (<b>4</b>), garcinone C (<b>5</b>), and xanthone I (9-hydroxycalabaxanthone) (<b>6</b>) were separated from the EtOAc-soluble fraction of the air-dried pericarps of <i>Garcinia mangostana</i> (Clusiaceae). Their structures have been verified on the basis of spectroscopic data analysis as well as comparison with the literature. The cytotoxic activity of <b>7</b> was assessed against MCF7, A549, and HCT116 cell lines using sulforhodamine B (SRB) assay. Compound <b>7</b> showed significant cytotoxic potential against MCF7 and A549 cell lines with IC<sub>50</sub>s 3.01 and 1.96 μM, respectively compared to doxorubicin (0.06 and 0.44 μM, respectively). However, it exhibited moderate activity towards HCT116 cell line.</p
