New vibsane diterpenes and lupane triterpenes from Viburnum odoratissimum.

Bioassay-directed fractionation of the methanolic extract of the leaves and flowers of Viburnum odoratissimum resulted in the isolation of two new diterpenes, vibsanol A (1) and vibsanol B (2), together with two new triterpenoids, 6beta-hydroxylup-20(29)-en-3-oxo-27,28-dioic acid (3) and 6alpha-hydroxylup-20(29)-en-3-oxo-27,28-dioic acid (4). In addition, the known terpenoids vibsanins B and E, and 6alpha-hydroxylup-20(29)-en-3-oxo-28-oic acid, were also isolated. The structures of the new compounds were established by chemical and spectroscopic means. Vibsanol A (1) and compound 3 exhibited significant cytotoxicity against human gastric (NUGC) tumor cells.