This study demonstrated that MJGT_F inhibited α-glucosidase in vitro and improved metabolic parameters in a dose-dependent manner in T2DM (type 2 diabetes mellitus) rats (reducing blood glucose, triglyceride, total cholesterol, low-density lipoprotein, insulin, and the homeostatic model assessment of insulin resistance; increasing high-density lipoprotein, insulin sensitivity index, and glucagon-like peptide-1). Here, GCG is linked to diabetes mellitus.