Two new bioactive triterpenoids from Melia volkensii (Meliaceae)

Meliavolin ( 1 ), a new triterpene with an apotirucallane skeleton, and meliavolkin ( 2 ), a new tetranortriterpene, together with melianin A, a known compound, have been isolated from the root bark of Melia volkensii (Meliaceae) by using activity-directed fractionation with brine shrimp. The structures have been elucidated by spectral data. The relative and absolute stereochemistry of meliavolin ( 1 ) was determined by analysis of Mosher ester derivatives, 1e and 1f , and by X-ray crystallographic analysis of meliavolin diacetate, 1c. 1 and melianin A showed marginal cytotoxicities to certain human tumor cell lines, but 2 was significantly more cytotoxic, showing equivalent potency to adriamycin against the human breast tumor cell line (MCF-7).