Inhibition of DNA Topoisomerases I and II and Cytotoxicity by Lignans from Saururus chinensis

Thirteen lignans, erythro-austrobailignan-6 (1), meso-dihydroguaiaretic acid (2), sauchinone (3), 1'-epi-sauchinone (4), saucerneol D (5), manassantin B (6), manassantin A (7), nectandrin B (8), machilin D (9), saucerneol F (10), saucerneol G (11), saucerneol H (12) and saucerneol I (13), were isolated from the ethyl acetate extract of the roots of Saururus chinensis. Among these compounds, 5 showed potent inhibitory activities against DNA topoisomerase I and II, and 5, 6, 7 and 10 showed mild cytotoxicities against HT-29 (IC50 values; 13, 12, 11, and 10 mu M, respectively) and HepG2 cell lines (IC50 values; 16, 11, 12, and 11 mu M, respectively).