Cytotoxicity and DNA topoisomerases inhibitory activity of constituents from the sclerotium of Poria cocos.

The bioactivity-guided fractionation of the methylene chloride extract of the sclerotium of Poria cocos led to the isolation of (S)-(+)-turmerone (1), ergosterol peroxide (2), polyporenic acid C (3), dehydropachymic acid (4), pachymic acid (5), and tumulosic acid (6). Compounds 4-6 exhibited moderate cytotoxicities, with IC50 values of 20.5, 29.1, and 10.4 microM, respectively, against a human colon carcinoma cell line. However, 3-6 not only showed inhibitory activities as potent as etoposide used as a positive control on DNA topoisomerase II (36.1, 36.2, 43.9 and 66.7% inhibition at a concentration of 20 microM, respectively), but also inhibition of DNA topoisomerase I (55.8, 60.7, 43.5, and 83.3% inhibition at a concentration of 100 microM, respectively).