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Bitter melon, the fruit of Momordica charantia L. (Cucurbitaceae), is a widely-used treatment for diabetes in traditionalmedicine systems throughout the world. Various compounds have been shown to be responsible for this reputed activity, and, in particular, cucurbitane triterpenoids are thought to play a significant role. The objective of this study was to investigate the gastrointestinal transport of a triterpenoid-enriched n-butanol extract of M. charantia using a two-compartment transwell human intestinal epithelial cell Caco-2 monolayer system, simulating the intestinal barrier. Eleven triterpenoids in this extract were transported from the apical to basolateral direction across Caco-2 cellmonolayers, andwere identified or tentatively identified by HPLC-TOF-MS. Cucurbitane triterpenoids permeated to the baso-lateral sidewith apparent permeability coefficient (Papp) values for 3-β-7-β,25-trihydroxycucurbita 5,23(E)-dien-19-al and momordicines I and II at 9.02 x 10-6,8.12 x 10-6, and 1.68 x 10-6 cm/s, respectively. Also, small amounts of these triterpenoids were absorbed inside the Caco-2 cells. This is the first report of the transport of the reputed antidiabetic cucurbitane triterpenoids in human intestinal epithelial cell monolayers. Our findings, therefore, further support the hypothesis that cucurbitane triterpenoids from bitter melon may explain, at least in part, the antidiabetic activity of this plant in vivo. [ABSTRACT FROM AUTHOR]

One new cucurbitane-type triterpenoid glycoside, momordicoside U (1), together with five known cucurbitane-type triterpenoids and related glycosides, 3β,7β,25-trihydroxycucurbita-5,23(E)-dien-19-al (2), momordicine I (3), momordicine II (4), 3-hydroxycucurbita-5,24-dien-19-al-7,23-di-O-β-glucopyranoside (5), and kuguaglycoside G (6), were isolated from the whole plant of Momordica charantia. Their structures were determined by chemical and spectroscopic methods. Momordicoside U (1) was evaluated for insulin secretion activity in an in vitro insulin secretion assay and displayed moderate activity. [ABSTRACT FROM AUTHOR]