Sesquiterpenes with quinone reductase-inducing activity from Liriodendron chinense.

Bioassay-directed separation of the methylene chloride extracts from the wood of Liriodendron chinense led to the isolation of six sesquiterpenes, tulipinolide (1), alpha-liriodenolide (2), beta-liriodenolide (3), lipiferolide (4), 11,13-dehydrolanuginolide (5), and tulipinolide diepoxide (6). Compounds 1-6 have not been found previously in L. chinense. The structures of the compounds were established on the basis of NMR spectroscopic data. All the compounds exhibited quinone reductase (QR)-inducing activity in Hepa lclc7 cells.