Saponins from the traditional medicinal plant Momordica charantia stimulate insulin secretion in vitro

The antidiabetic activity of Momordica charantia (L.). Cucurbitaceae, a widely-used treatment for diabetes in a number of traditional medicine systems, was investigated in vitro. Antidiabetic activity has been reported for certain saponins isolated from M. charantia. In this study insulin secretion was measured in MIN6 beta-cells incubated with an ethanol extract, saponin-rich fraction, and five purified saponins and cucurbitane triterpenoids from M. charantia, 3 beta,7 beta,25-trihydroxycucurbita-5,23(E)-dien-19-al (1), momordicine I (2), momordicine II (3). 3-hydroxycucurbita-5,24-dien-19-al-7,23-di-O-beta-glucopyranoside (4), and kuguaglycoside G (5). Treatments were compared to incubation with high glucose (27 mM) and the insulin secretagogue, glipizide (50 mu M). At 125 mu g/ml, an LC-ToF-MS characterized saponin-rich fraction stimulated insulin secretion significantly more than the DMSO vehicle, p = 0.02. At concentrations 10 and 25 mu g/ml, compounds 3 and 5 also significantly stimulated insulin secretion as compared to the vehicle, p <= 0.007, and p = 0.002, respectively. This is the first report of a saponin-rich fraction, and isolated compounds from M. charantia, stimulating insulin secretion in an in vitro, static incubation assay. (C) 2011 Elsevier GmbH. All rights reserved.