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 $IC_{50}$ values of 20.5, 29.1, and $10.4{\;}\mu\textrm{m}$, 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 $20{\;}\mu\textrm{m}$, respectively), but also inhibition of DNA topoisomerase I (55.8, 60.7, 43.5, and 83.3％ inhibition at a concentration of $100{\;}\mu\textrm{m}$, respec-tively).