Rare prenylated isoflavonoids from the young twigs of Millettia extensa and their cytotoxic activities

Three new isoflavonoids, millexatins N–P (1–3), along with seven known compounds (6–10), were isolated from the acetone extract of the young twigs of Millettia extensa. The structures were characterized by NMR spectroscopic and mass spectrometric analyses. Millexatin N (1) is an unusual geminal diisoprenylated isoflavone with a modified ring A. Millexatin P (3) is an unusual isoflavone with a cyclohexyl substituent on ring B, which is extremely rare in nature. The isolated metabolites (1, 2, and 6–10) were evaluated for cytotoxicities against MDA-MB231, Huh-7, KKU-100 and normal human dermal fibroblast (NHDF) cell lines. Only compounds 1, 6 and 8 showed cytotoxicities against all cell lines with IC(50) values ranging from 13.9 to 30.9 μM.