摘要：Fourteen compounds were isolated from the flowers of Inula japonica THUNB. ( Asteraceae ), including two new compounds, (1 S ,2 S ,4 S ,5 S ,8 S ,10 R )-2-acetoxy-4,3-dihydroxy-pseudoguai-7(11)-en-12,8-olide ( 1 ) and (1 S ,2 S ,4 S ,5 S ,8 S ,10 R )-2,4,13-trihydroxy-pseudoguai-7(11)-en-12,8-olide ( 2 ), and twelve known compounds, budlein B ( 3 ), 6β-hydroxytomentosin ( 4 ), 6-deacetoxybritanin ( 5 ), 4-epipulchellin ( 6 ), britanin ( 7 ), tomentosin ( 8 ), (+)-dihydroquercetin ( 9 ), (−)-syringaresinol ( 10 ), quercetagetin 3,4′-dimethyl ether ( 11 ), luteolin ( 12 ), britanin G ( 13 ) and inuchinenolide C ( 14 ). Structures of 1 and 2 were determined based on one and two dimensional (1D)- and (2D)-NMR data and Mosher’s esterification method. Compounds 9 and 12 showed inhibitory activities toward DNA topoisomerase I with IC50 values of 55.7 and 37.0 µM, respectively, compared to camptothecin (CPT) with an IC50 of 24.5 µM. Compounds 7 – 9 and 11 – 14 exhibited more potent inhibitory activity against topoisomerases II with IC50 values of 6.9, 3.8, 3.0, 6.9, 10.0, 14.7 and 13.8 µM, respectively, than that of etoposide (VP-16) with an IC50 of 26.9 µM. Compounds 4 – 7 and 10 – 14 exhibited weak cytotoxicities to the selected cancer cell lines.
关键词：Inula japonica;topoisomerase I;topoisomerase II
