Cucurbitane-type triterpenoids from the fruit of Momordica charantia

The structures of three new cucurbitane-type triterpenoids isolated from the methanol extract of the fruit of Japanese Momordica charantia were established as (19R,23E)-5 beta, 19-epoxy- 19-methoxycucurbita-6,23,25-trien-3 beta-ol (1), (23E)-3 beta-hydroxy-7 beta-methoxycucurbita-5,23,25-trien-19-al (2), and (23E)-3 beta-hydroxy-7 beta,25-dimethoxycueurbita-5,23-dien-19-al (3) on the basis of spectroscopic methods. These compounds were accompanied by the known (19R,23E)-5 beta,19-epoxy-19,25-dimethoxycueurbita-6,23-dien-3 beta-ol (4) and (19R,23E)-5 beta,19-epoxy-19-methoxycucurbita-6,23-diene-3 beta,25-diol (5). This is the first report of the isolation of tetracyclic triterpenoids possessing a Delta(23,25)-conjugated diene system, viz., 1 and 2, from a natural source.