Topoisomerase I and II Inhibitory Constituents from the Bark of Tilia amurensis

Two coumarins (1 and 6), one flavan-3-ol (2), one fatty acid (3), and two lignan glycosides (4 and 5) were isolated from the EtOAc and CH2Cl2 extract of the bark of Tilia amurensis. Their chemical structures were identified by comparing their physicochemical and spectral data with those of published in literatures. Compounds 4, 5, and 6 were isolated from Tilia genus for the first time. Compounds 2 and 3 showed potent inhibitory activity against both DNA topoisomerase I (IC50 values; 49 mu M and 4 mu M, respectively, with 18 mu M of positive control compound, comptothecin) and DNA topoisomerase II (IC50 values; 13 mu M and 3 mu M, respectively, with 50 mu M of positive control compound, etoposide). However, all compounds did not showed cytotoxicity against the human colon adenocarcinoma cell line (HT-29), the human breast adenocarcinoma cell line (MCF-7), and human liver hepatoblastoma cell line (HepG-2).