Chemical composition, antioxidant, and anti-diabetic activities of ethyl acetate fraction of Stachys riederi var. japonica (Miq.) in streptozotocin-induced type 2 diabetic mice

This work analysed the chemical composition, antioxidant, and enzyme inhibitory activities of solvent extract (SJ-ME) and fractions (SJ-HF, SJ-EAF, and SJ-MF) of the Stachys riederi var. japonica (Miq.) (SJ). Furthermore, the effect of SJ-EAF in STZ induced type 2 diabetic mice was examined. Among the samples, SJ-EAF exhibited a lower IC50 concentration of 64.2 +/- 0.48 mu g/mL for DPPH and 82.6 +/- 0.09 mu g/mL for ABTS(+). The SJ-EAF concentration of 2.89 +/- 0.03 mu g and 2.27 +/- 0.98 mu g was equivalent to 1 mu g of acarbose mediated enzyme inhibitory effect against alpha-amylase and alpha-glucosidase, respectively. The SJ-EAF did not show cytotoxicity (<80%) to NIH3T3 nor HepG2 cells but enhanced the glucose uptake in the IR-HepG2. LC-MS/MS of SJ-EAF showed the presence of a total of 16 compounds. Among the identified compounds, rosmarinic acid, caffeic acid, oleanolic acid, and ursolic acid showed high catalytic activity of alpha-amylase and alpha-glucosidase. The treatments of SJ-EAF restored the level of blood glucose, body weight, insulin, HDL and mRNA level of IRS1, GLUT2, GLUT4 and Akt whereas it reduced the excess elevation of total cholesterol, total triglycerides, LDL, AST, ALT, ALP, BUN, and creatinine in STZ induced diabetic mice. Overall, the present study concluded that the SJ-EAF exhibited promising antidiabetic activity.