Amyrisins A-C, O-prenylated flavonoids from Amyris madrensis.

Three new O-prenylated flavonoids, amyrisins A-C (1-3), were isolated from the leaves and twigs of Amyris madrensis, along with the known compound polygamain (4). The structures of 1-3 were elucidated on the basis of the analysis of spectroscopic data interpretation. Amyrisins B (2) and C (3) showed moderate cytotoxicity against PC-3 and DU 145 prostate cancer cells with IC(50) values of 17.5 and 23 μM, respectively, while amyrisin A (1) did not show any cytotoxicity at the highest concentration tested, 50 μM. Polygamain (4) exhibited potent antiproliferative and microtubule-depolymerizing activities.