New iridoids from Patrinia scabiosaefolia and their hypoglycemic effects by activating PI3K/Akt signaling pathway

Growing in regions of Asia and North America, Patrinia scabiosaefolia is a wild vegetable and herb that has demonstrated health-promoting properties. Iridoids are one of the most bioactive phytochemicals in P. scabiosaefolia but the in-depth study is scarce. Herein we reported the separation and characterization of nine iridoids (compounds 1-9) from P. scabiosaefolia, and two compounds (2 and 6) were new. All the structures of the nine iridoids were characterized and confirmed with NMR (1D & 2D), HRMS, IR and UV. Compound 2 is a five-member ring iridoid, reminiscent of a broken C-1 and C-2 bond. Compound 6 has a typical monoene valerian iridoid, but the 5-deoxyglucose moiety at C-11 position is uncommon in this genus. The anti-diabetic evaluation of the isolated compounds revealed that compounds 1, 2, and 9 significantly increased the glucose absorption in 3 T3-L1 cells (P < 0.01). Further mechanism investigations have demonstrated that compound 1 promoted glucose uptake in dexamethasone-treated 3 T3-L1 adipocytes by activating PI3K/Akt signaling pathway. The expression of GLUT4 mRNA and protein was also upregulated. These results provide scientific references for the potential use of P. scabiosaefolia as a functional food to manage hyperglycemia.