Clerodane diterpenoids from the vine stems of Fibraurea recisa Pierre and their hepatic gluconeogenesis inhibitory activity

Fibraurea recisa Pierre is a vine plant and its vine stems are used as a traditional Chinese medicine to treat heat toxin, constipation, diarrhea, sore throat, eye inflammation, carbuncles, and skin ulcers. The alkaloid chemical composition of this plant has been extensively studied; however, investigations into non-alkaloid components remain limited. In this study, phytochemical studies of the vine stems of F. recisa were conducted, leading to the isolation and identification of twenty highly oxidized clerodane diterpenoids, including ten previously undescribed compounds, designated fibrecins A-J (1–10). The structures and absolute configurations of 1–10 were determined through comprehensive spectroscopic methods (IR, HRESIMS, 1D and 2D NMR), electronic circular dichroism data, and single-crystal X-ray diffraction. Notably, compounds 1 and 2 are rare 18-nor-clerodane diterpenoids. Excessive hepatic gluconeogenesis is an important cause of hyperglycemia and type 2 diabetes mellitus. Herein, compounds 1, 9, 14, and 15 were found to exhibit moderate hepatic gluconeogenesis inhibitory activity in primary mouse hepatocytes, suggesting that these compounds might have potential effect on ameliorating the hyperglycaemia.