Primary Studies On Purification, Structural Identification And Inhibitory Activities Of Fat Deposition Of Triterpenoid Constituents From Momordica Charantia L.

Momordica charantia L. (Cucurbitaceae) is known as a kind of edible vegetable in Asian countries. It has also been extensively used in folk to treat obesity and diabetes. In the past, researches of chemical constituents and phytochemical activities mainly concerted on the fruits of M. charantia, however, resesrches on the stems and leaves of M. charantia were fewer. The triterpenoids were isolated from the stems and leaves of M. charantia in our study. Meanwhile, they were evaluated for the inhibitory activities of fat deposition.To further study the chemical constituent of novel structure and good biological activity, the triterpenoids were isolated from the stems and leaves of M. charantia from Xinjiang. The dried stems and leaves of M. charantia (20 kg) were ground into powder and extracted three times with MeOH and concentrated in vacuo to give a crude extract, which was then partitioned into petroleum ether, ethyl acetate and n-BuOH fractions. The ethyl acetate fraction (432 g) was chromatographed over HP-20 macroreticular resin column chromatography (CC) to afford four parts (MeOH/H2O:45%,60%,75%,85%).75% part was subjected to chromatographic purification using RP-18, and repeated by chromatographic column of silica gel, followed by semi-preparative HPLC, and finally yielded fifteen cucurbitane-type triterpenoids (1-15), including seven new compounds (1-7). The structures of new compounds were identified as cucurbita-6,24-dien-3β,23-diol-19,5β-olide (1), (19R)-5β,19-epoxy-19-methoxy-cucurbita-6,24-dien-3β,23-diol(2), (195)-5β,19-epoxy-19-methoxycucurbita-6,24-dien-3 (3,23-diol (3), (19R)-5β,19-epoxy-19-isopropoxycucurbita-6,24-dien-3β,23-diol(4),3β,23-dihydroxy-5-methoxycucurbita-6,24-dien-19-al (5), (19R)-7β,19-epoxy-19-methoxycucurbita-5,24-dien-3β,23-diol (6) and 7β-methoxy-cucurbita-6,24-dien-3β,9,23-triol (7), by extensive MS, 1D and 2D NMR spectroscopic technologies. This is the first discovery of the isolation of cucurbitane-type triterpenoids possessing a 7β,19-epoxy system, viz., (19R)-7β,19-epoxy-19-methoxycucurbita-5,24-dien-3β,23-diol (6), from Momordica charantia L. In order to find effective conponents of inhibitory activities of fat deposition, selected compounds were evaluated for the activities of reducing 3T3-L1 adipocyte fat deposition. The results showed that 6 displayed moderate inhibitory activity of fat deposition.