A Pair of New Apotirucallane Triterpenes, Meliavolkensins A and B, from Melia volkensii (Meliaceae).

Abstract Two new bioactive apotirucallane triterpenes, meliavolkensins A ( 1 ) and B ( 2 ), were isolated from the root bark of Melia volkensii (Meliaceae). These two compounds have a new type of substituted tetrahydropyran ring side chain, and their structures have been elucidated by spectroscopic analyses. 1 and 2 also show cytotoxic selectivities to a hyman colon tumor cell line (H-29).