Topoisomerase Ⅰ and Ⅱ Inhibitory Activities and Cytotoxic Constituents from the Barks of Tilia amurnesis

Eight compounds, squalene (1), friedelin (2), β-sitosterol (3), β-sitosterol-3-O-glucoside (4), -tocopherol (5), betulinic acid (6), trilinolein (7) and 1-O-(9Z,12Z-Octadecadienoyl)-3-nonadecanoyl glycerol (8), were isolated from the barks of Tilia amurensis. Their chemical structures were identified by comparing their physicochemical and spectral data with those published in the literature. These isolated compounds were examined for their inhibitory activities against topoisomerase Ⅰ and Ⅱ. Compound 7 showed significant inhibition of DNA topoisomerase Ⅰ and Ⅱ activities, with percent decreases in activity of 87 and 95%, respectively at a concentration of 100 μM. Compound 6 exhibited cytotoxicity against the human colon adenocarcinoma cell line (HT-29), the human breast adenocarcinoma cell line (MCF-7) and the human liver hepatoblastoma cell line (HepG-2), with IC∧50 values of 20, 59 and 16 μM, respectively.