Structural elucidation of two new ursane-type triterpenoids from Syzygium handelii by spectroscopic analyses and calculations

Two new ursane-type triterpenoids with a rare caffeoyl group at C-27, 3β-acetoxy-27-trans-caffeoyloxyurs-12-en-28-oic acid-methyl ester (1) and 3β-acetoxy-27-cis-caffeoyloxyurs-12-en-28-oic acid-methyl ester (2), together with three known triterpenoids (3-5), were isolated from the leaves and twigs of Syzygium handelii. Their structures were elucidated by detailed NMR, MS spectroscopic data interpretation, calculated NMR, and DP4+ methods. Anti-microbial and cytotoxic activities of new compounds were evaluated. Compounds 1 and 2 showed weak cytotoxicity against HepG2 cells with IC50 value of 81.3 and 72.1 μM, respectively. The optimal molecule docking results showed that compounds 1 and 2 could bind stably to COX-2 protein.