A pair of new tirucallane triterpenoid epimers from the stems of Picrasma quassioides

A pair of new tirucallane triterpenoid epimers, picraquassins M and N ( 1 and 2 ), were isolated from the stems of Picrasma quassioides (D. Don) Benn. Their structures were determined based on comprehensive spectroscopic and X-ray crystallographic analyses. In addition, their AChE inhibitory activity, cytotoxicity against five human tumour cell lines (SW480, MCF-7, HepG2, Hela, and PANC-1), and antimicrobial activity against two bacteria (Staphylococcus. aureus 209P and Escherichia coli ATCC0111) and two fungi (Candida albicans FIM709 and Aspergillus niger R330) were evaluated.