In recent years, considerable attention has been given to hypoglycaemic agents deriving from plants products, especially on potent antioxidant flavonoids showing positive effects in the management of diabetes mellitus, in improving glucose metabolism and in their action on targets involved in type 2 diabetes mellitus such as α-glycosidase and DPP-4 [242,243,244,245,246,247,248,249,250,251,252,253,254,255,256,257,258,259]. This evidence concerns the gene DPP4 and diabetes mellitus.