Calaxanthones A-C, three new xanthones from the roots of <i>Calophyllum calaba</i> and the cytotoxicity

<p>Three new xanthones, named calaxanthones A<b>-</b>C (<b>1</b>–<b>3</b>), along with 17 known xanthones (<b>4</b>–<b>20</b>) were isolated from the roots of <i>Calophyllum calaba</i>. Their structures were determined by spectroscopic analysis. All isolated compounds were evaluated for their cytotoxicity against five cancer cell lines (KB, HeLa S-3, HT-29, MCF-7 and HepG-2). Compound <b>3</b> showed potent cytotoxicity against all the five cancer cell lines with IC₅₀ values in the range of 0.82–5.04 μM. Furthermore, compound <b>6</b> showed potent cytotoxicity against KB, HeLa S-3 and HepG2 cells with IC₅₀ values of 7.06, 5.27 and 9.64 μM, respectively. Additionally, compound <b>7</b> showed potent cytotoxicity against KB cell with an IC₅₀ value of 4.62 μM.