New iridoids from Lyonia ovalifolia and their anti-hyperglycemic effects in mice pancreatic islets

Abstract Phytochemical investigation on the aerial parts of Lyonia ovalifolia (Wall.) Drude led to the isolation of three new iridoids, lyonofolin A ( 1 ), lyonofolin B ( 2 ), and lyonofolin C ( 3 ), and a known iridoid, gelsemiol ( 4 ). Structures of compounds 1 – 4 were determined by extensive spectroscopic analyses, including EI-MS, HREI-MS, UV, IR, and 1D- and 2D-NMR (HMBC, HSQC, COSY, NOESY) spectroscopic methods. The effect of insulin secretion of compounds 1 , 2 , and 4 were evaluated in mice pancreatic islets cellular model. This insulin secretory assay demonstrated that compound 2 potentiates glucose-induced insulin secretion, and thus can serve as a new insulin secretagogue for the treatment of diabetes. The newly isolated compounds were further evaluated against normal 3 T3 cell lines for cytotoxicity, where they did not show any cytotoxicity.