A new monoepoxylignan, dysosmarol (1), along with eight known compounds, podophyllotoxin (2), 4'-demethylpodophyllotoxin (3), deoxypodophyllotoxin (4), 4'-demethyldeoxypodophyllotoxin (5), diphyllin (6), kaempferol, quercetin, and beta-sitosterol, were isolated from the roots of Dysosma versipellis. The structure of 1 was elucidated by spectroscopic methods. Aryltetralin lignans 2-4 showed the most potent inhibitory activities against the growth of androgen-sensitive (LNCaP) and androgen-independent (PC-3) human prostate cancer cell lines, with IC50 values in the ranges 0.030-0.056 and 0.032-0.082 microM, respectively. A quantitative HPLC analysis showed that compound 2 occurred at the highest concentration in the plant (37.21 mg/g) followed by compound 4 (5.01 mg/g) and compound 3 (2.75 mg/g). Furthermore, D. versipellis roots contain a similar content of compound 2 as compared with the rhizomes and roots of Podophyllum hexandrum, a commercial source of the lignan. Thus, cultivation of D. versipellis in suitable locations may serve as an alternative source for podophyllotoxin (2) production.