Plant Foods and Their Phytochemicals as DPP IV and PTP1B Inhibitors for Blood Glucose Regulation: A Review

The increasing prevalence of diabetes has led to reducing hyperglycemia through mechanisms other than the conventional mechanism, such as α-amylase and α-glucosidase inhibition. In recent years, medicinal drugs focusing on inhibiting dipeptidyl peptidase IV (DPP IV) and protein tyrosine phosphatase 1B (PTP1B) enzymes have emerged and are being used for type 2 diabetes management. DPP IV inhibitors reduce blood glucose levels by preventing the degradation of incretin hormones such as glucagon-like peptide and glucose-dependent insulinotropic polypeptide. PTP1B has also been known to play a crucial role in reducing insulin resistance and is one of the most promising targets for managing Type 2 diabetes. Inhibition of these two enzymes is also expected to benefit other metabolic conditions such as cancer, obesity, lowered immunity, etc. The existing synthetic DPP IV and PTP1B inhibitors have been known to cause side effects. Inhibitors from natural sources are expected to be safer. The search for PTP1B inhibitors is especially necessary since the primary treatment for type 2 diabetes is to reduce insulin resistance. None of the existing PTP1B inhibitors are clinically well-approved to date. Hence, searching for antihyperglycemic components from natural sources such as foods has become a pressing need. This review has attempted to collate and analyze the existing scientific evidence to identify plant foods and their phytochemicals with in vitro and in vivo DPP IV and PTP1B inhibitory activity comprehensively. With further scientific validation and safety studies, the identified phytochemicals could be used for pharmacological applications. The foods and their extracts could be advantageous in formulating functional foods and diets suitable for type 2 diabetes, along with other physiological benefits.