An Isoflavone from Leiophyllum buxifolium and Its Antiproliferative Effect.

A new C-methylisoflavone, isosideroxylin (1), and a known C-methylflavone, sideroxylin (2), were isolated from the EtOAc extract of the leaves of Leiophyllum buxifolium. The two compounds were evaluated with the sulforhodamine B assay for their antiproliferative effects against ER(-) MDA-MB-231 and ER(+) MCF-7 breast cancer cell lines and the NIH3T3 mouse fibroblast cell line. Isosideroxylin (1) displayed a selective antiproliferative effect against MDA-MB-231 cells.