Vibsane diterpenoids from the leaves and flowers of Viburnum odoratissimum.

In addition to the five known compounds 5-epi-vibsanin H, vibsanins C, H, and G, and aldovibsanin B, four new diterpenes, 5-epi-vibsanin G (1), 18-O-methylvibsanin G (2), vibsanin M (3), and aldovibsanin C (4), were isolated from an acetone extract of the leaves and flowers of Viburnum odoratissimum by bioassay-directed fractionation. In addition, two acetyl derivatives 5 and 6 were obtained from the naturally occurring diterpenes. The structures of the new compounds were established on the basis of NMR spectral analysis, including COSY, HMQC, HMBC, and NOESY correlations. The compounds were evaluated for cytotoxicity against human nasopharyngeal carcinoma (HONE-1) tumor cells and human gastric cancer (NUGC-3) cells.