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Two new 27-norcucurbitane triterpenoids, 27-nor-3beta-hydroxy-7beta-methoxycucurbita-5,23(E)-dien-25-one (1) and 27-nor-3beta-hydroxy-5beta,19-epoxycucurbita-6,23(E)-dien-25-one (2), together with two known cucurbitane triterpenes, 23(E)-7beta-methoxycucurbita-5,23,25-trien-3beta-ol (3) and 5beta,19-epoxy-25-methoxycucurbita-6,23(E)-dien-3beta-ol (4), were isolated from the fruits of Momordica charantia var. abbreviata. Their structures were determined by analysis of spectroscopic data and comparison with the data of known analogues.

Insulin resistance is a causative factor for type 2 diabetes, whereas the development of insulin resistance is closely related to chronic inflammation induced by factors such as tumor necrosis factor-α (TNF-α). Momordica charantia, also known as bitter melon, has been used as an herbal medicine and reported to ameliorate inflammation and hyperglycemia. Previously, a triterpene 5β,19-epoxy-25-methoxy-cucurbita-6,23-diene-3β,19-diol (EMCD), purified from M. charantia L. wild variant WB24, was found to activate AMP-activated protein kinase (AMPK) and have a hypoglycaemic effect in TNF-α-treated FL83B cells. AMPK has been a target for developing anti-diabetic medicine and suggested to play a role in anti-inflammation. The current study aims to investigate if EMCD might repress TNF-α-induced inflammation via AMPK. TNF-α-induced inflammation in FL83B cells was characterized using Western blotting and reverse transcriptase-polymerase chain reaction. Consequently, the expression of inflammatory markers including inducible nitric oxide synthase (iNOS), the p65 subunit of nuclear factor-κB (NF-κB), protein-tyrosine phosphatase-1B, TNF-α and interleukin-1β were significantly elevated by TNF-α in the cell, and EMCD obviously suppressed the TNF-α-induced expression of these markers. When the effect of EMCD was tested simultaneously with epigallocatechin-3-gallate (EGCG), a catechin from green tea reported to be anti-inflammatory, EMCD showed a more obvious anti-inflammatory activity than EGCG did. Investigation of the underlying mechanism suggested that EMCD inhibited the activation of the IκB kinase (IKK) complex and the NF-κB pathway, and the effect was likely independent of AMPK. Collectively, the multiple functions of EMCD suggest it to be a potential agent in treating diabetic complications and other inflammation-related disorders., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Two novel pentanorcucurbitane triterpenes, 22-hydroxy-23,24,25,26,27-pentanorcucurbit-5-en-3-one (1) and 3,7-dioxo-23,24,25,26,27-pentanorcucurbit-5-en-22-oic acid (2) together with a new trinorcucurbitane triterpene, 25,26,27-trinorcucurbit-5-ene-3,7,23-trione (3) were isolated from the methyl alcohol extract of the stems of Momordica charantia. The structures of the new compounds were elucidated by spectroscopic methods. Compounds 2 and 3 showed potent cytoprotective activity in tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity of HepG2 cells.

Four novel octanorcucurbitane triterpenes, octanorcucurbitacins A-D (1-4), together with one known octanorcucurbitane triterpene, kuguacin M (5), were isolated from the methyl alcohol extract of the stems of Momordica charantia. Their structures were elucidated on the basis of extensive spectroscopic analyses. Compound 3 inhibited tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity against HepG2 cells.

Four new cucurbitane-type triterpenes, cucurbita-5,23(E)-diene-3beta,7beta,25-triol (1), 3beta-acetoxy-7beta-methoxycucurbita-5,23(E)-dien-25-ol (2), cucurbita-5(10),6,23(E)-triene-3beta,25-diol (5), and cucurbita-5,24-diene-3,7,23-trione (6), together with four known triterpenes, 3beta,25-dihydroxy-7beta-methoxycucurbita-5,23(E)-diene (3), 3beta-hydroxy-7beta,25-dimethoxycucurbita-5,23(E)-diene (4), 3beta,7beta,25-trihydroxycucurbita-5,23(E)-dien-19-al (7), and 25-methoxy-3beta,7beta-dihydroxycucurbita-5,23(E)-dien-19-al (8), were isolated from the methyl alcohol extract of the stems of Momordica charantia. The structures of the new compounds were elucidated by spectroscopic methods.

Five new cucurbitane-type triterpenes, (23E)-25-methoxycucurbit-23-ene-3beta,7beta-diol (1), (23E)-cucurbita-5,23,25-triene-3beta,7beta-diol (2), (23E)-25-hydroxycucurbita-5,23-diene-3,7-dione (3), (23E)-cucurbita-5,23,25-triene-3,7-dione (4), and (23E)-5beta,19-epoxycucurbita-6,23-diene-3beta,25-diol (5), together with one known triterpene, (23E)-5beta,19-epoxy-25-methoxycucurbita-6,23-dien-3beta-ol (6), have been isolated from the methanol extract of the stems of Momordica charantia. The structures of the new compounds were elucidated by spectroscopic methods.