Sesquiterpene esters from celastrus orbiculatus and their structure-activity relationship on the modulation of multidrug resistance

Abstract

Six new (1-6) and three known (7-9) sesquiterpene esters were isolated from the roots of Celastrus orbiculatus. The structures of the new compounds were elucidated as 1β-acetoxy-6α-furoyloxy-9α-benzoyloxydihydro-β- agarofuran (1), 1β-acetoxy-6α-benzoyloxy-9α-furoyloxydihydro-β-agarofuran (2), 1β-acetoxy-6α,9α-difuroyloxydihydro-β-agarofuran (3), 1β,2β- diacetoxy-6α-furoyloxy-9α-benzoyloxydihydro-β-agarofuran (4), 1β- acetoxy-2β,6α-difuroyloxy-9α-benzoyloxydihydro-β-agarofuran (5), and 1β- acetoxy-2β,6α,9α-tribenzoyloxydihydro-β-agarofuran (6). Compounds 4, 5, and 7-9 were shown to be more active than verapamil in reversing vinblastine resistance in multidrug-resistant KB-V1 cells.