Dyscusins A-C, three new steroids from the leaves of Dysoxylum cumingianum

Three new steroids dyscusins A-C (1-3), including a stigmastane-type sterol and two pregnanes, together with two known steroids were isolated from the leaves of Dysoxylum cumingianum (Meliaceae). Their structures were elucidated on the basis of extensive spectroscopic analyses. In a cytotoxicity assay, compound 1 showed ten-fold enhanced cytotoxicity against multi-drug resistant cancer cells (KB-C2) in the presence of 2.5 μM colchicine as compared with the absence of colchicine. This notable finding indicated that 1 possessed a multi-drug resistant reversal effect.