Cytotoxic flavonoids from two <i>Lonchocarpus</i> species

<p>A new isoflavone, 4′-prenyloxyvigvexin A (<b>1</b>) and a new pterocarpan, (6a<i>R</i>,11a<i>R</i>)-3,8-dimethoxybitucarpin B (<b>2</b>) were isolated from the leaves of <i>Lonchocarpus bussei</i> and the stem bark of <i>Lonchocarpus eriocalyx</i>, respectively. The extract of <i>L. bussei</i> also gave four known isoflavones, maximaisoflavone H, 7,2′-dimethoxy-3′,4′-methylenedioxyisoflavone, 6,7,3′-trimethoxy-4′,5′-methylenedioxyisoflavone, durmillone; a chalcone, 4-hydroxylonchocarpin; a geranylated phenylpropanol, colenemol; and two known pterocarpans, (6a<i>R</i>,11a<i>R</i>)-maackiain and (6a<i>R</i>,11a<i>R</i>)-edunol. (6a<i>R</i>,11a<i>R</i>)-Edunol was also isolated from the stem bark of <i>L. eriocalyx</i>. The structures of the isolated compounds were elucidated by spectroscopy. The cytotoxicity of the compounds was tested by resazurin assay using drug-sensitive and multidrug-resistant cancer cell lines. Significant antiproliferative effects with IC<sub>50</sub> values below 10 μM were observed for the isoflavones 6,7,3′-trimethoxy-4′,5′-methylenedioxyisoflavone and durmillone against leukemia CCRF-CEM cells; for the chalcone, 4-hydroxylonchocarpin and durmillone against its resistant counterpart CEM/ADR5000 cells; as well as for durmillone against the resistant breast adenocarcinoma MDA-MB231/<i>BCRP</i> cells and resistant gliobastoma U87MG<i>.</i>Δ<i>EGFR</i> cells.</p>