Cytotoxic flavonoids from two Lonchocarpus species.

A new isoflavone, 4'-prenyloxyvigvexin A ( 1 ) and a new pterocarpan, (6a R ,11a R )-3,8-dimethoxybitucarpin B ( 2 ) were isolated from the leaves of Lonchocarpus bussei and the stem bark of Lonchocarpus eriocalyx , respectively. The extract of L. bussei 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 R ,11a R )-maackiain and (6a R ,11a R )-edunol. (6a R ,11a R )-Edunol was also isolated from the stem bark of L. eriocalyx . 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 IC50 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/ BCRP cells and resistant gliobastoma U87MG . Δ EGFR cells.