Cucurbitane-type Triterpenoids Research Articles

Cucurbitacins from Cayaponia racemosa: isolation and total assignment of 1H and 13C NMR spectra

Two new cucurbitane-type triterpenoids, 2beta,3beta,16alpha,20(R),25-pentahydroxy-9-methyl-19-norlanost-5-en-7,22-dione and 2beta,3beta,16alpha,20(R),25-pentahydroxy-9-methyl-19-norlanost-5-en-7,11,22-trione, were isolated from fruits of Cayaponia racemosa. The total (1)H and (13)C chemical shift assignment of these two closely related compounds is described, making use of one- and two-dimensional NMR techniques.

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)-5beta,19-epoxy-19-methoxycucurbita-6,23,25-trien-3beta-ol (1), (23E)-3beta-hydroxy-7beta-methoxycucurbita-5,23,25-trien-19-al (2), and (23E)-3beta-hydroxy-7beta,25-dimethoxycucurbita-5,23-dien-19-al (3) on the basis of spectroscopic methods. These compounds were accompanied by the known (19R,23E)-5beta,19-epoxy-19,25-dimethoxycucurbita-6,23-dien-3beta-ol (4) and (19R,23E)-5beta,19-epoxy-19-methoxycucurbita-6,23-diene-3beta,25-diol (5). This is the first report of the isolation of tetracyclic triterpenoids possessing a delta23,25-conjugated diene system, viz., 1 and 2, from a natural source.