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

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. [Display omitted] •Three new, and a known iridoids were isolated from lyonia ovalifolia.•Compounds were identified as lyonofolin A (1), lyonofolin B (2), lyonofolin C (3), and gelsemiol (4).•Compounds 1, 2, and 4 were evaluated for their insulin secretion in mice pancreatic islets.•Compound 2 potentiated a glucose-induced insulin secretion, and thus identified as a new insulin secretagogue.