Isolation and cytotoxicity evaluation of taxanes from the barks of Taxus wallichiana var. mairei

Fifteen taxanes (1-15) including a new taxane glucoside, 7β,9α,10β-triacetoxy-13α-hydroxy-5α-O-(β-d-glucopyranosyl)taxa-4(20),11-diene (1), were isolated from the barks of Taxus wallichiana var. mairei. Compounds 1-15 representing three sub-types of 6/8/6-taxane were evaluated in vitro for anti-proliferative activity against a panel of parental and drug-resistant Cancer cells. Potent compounds were found while several exhibited selective cytotoxicity. Especially, 3, 8, and 10 showed selective inhibition to breast carcinoma cell line MCF-7, while 13 selectively inhibited taxol resistant human ovarian carcinoma cell line A2780/TAX (IC50=0.19μM), being more potent than the clinical drugs taxol (IC50=4.4μM) and docetaxol (IC50=0.42μM), and less cytotoxic to mouse embryonic fibroblast cell line NIH-3T3, a cell line close to normal cell line. The possible P-glycoprotein evasion mechanism of 13 against A2780/TAX and the preliminary structure-activity relationships (SARs) of this group of compounds were also discussed.