ADDITIONAL BIOACTIVE TRITERPENOIDS FROM MELIA-VOLKENSII (MELIACEAE)

Meliavolen (1) and melianinone (2), new triterpenes with an apotirucallane skeleton, together with two known compounds, 3-episapelin A (5) and nimbolin B (6), have been isolated from the root bark of Melia volkensii (Meliaceae) by using brine shrimp lethality for bioactivity-directed fractionation. The structures have been elucidated by spectral data. The relative and absolute stereochemistries of 2 were determined by correlating 2 with melianin A (3). The stereochemistry of 3 was determined by X-ray crystallographic analysis and Mosher methodology. The stereochemistry of 5 was also determined by Mosher methodology. The four isolated compounds, meliavolen (1), melianinone (2), 3-episapelin (5), and nimbolin B (6), were all moderately active in the brine shrimp lethality test and were significantly cytotoxic among human solid tumor cell lines with noted selectivities toward the colon cell line (HT-29).