Cucurbitane-type glycosides from the fruits of Momordica charantia and their hypoglycaemic and cytotoxic activities

Eight new cucurbitane-type glycosides, kuguasaponins A-H (1-8), and six known compounds (9-14), were isolated by the bioassay-directed fractionation of the fruits of Momordica charantia. The structures of the compounds were established via spectroscopic analyses, including NMR, IR, and MS techniques. The stereochemistry of the isolated cucurbitanes was further determined using X-ray crystallographic analysis, NOESY experiments, and acid hydrolysis, as well as comparison with the cucurbitanes reported in the literature. The HPLC profiles of the active fraction by an ELSD detector were established and used to identify the 7 main peaks of the isolated cucurbitanes. Pharmacological studies on the anti-hyperglycaemic effects revealed that compounds 2, 3, 7, 8, and 13 exhibited strong bioactivities at 10 μM based on the glucose uptake assay. In addition, compounds 2-5, and 14 exhibited moderate cytotoxicity against MCF-7, Doay, HEp-2, and WiDr human tumour cell lines and no activity against the M10 cell line.