Antioxidants and Antidiabetic Potential of Polyphenolic Fractions and Crude Extracts of Rhus typhina Fruit, Punica granatum L. Peel, and Terminalia catappa L. Leaves: In Vitro and In Vivo Evaluation.

Rhus typhina (sumac) fruit, Punica granatum (pomegranate) peel, and Terminalia catappa (Indian almond) leaves' extracts and their anthocyanin and non-anthocyanin fractions were assessed in vitro for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing power (FRAP), human salivary amylase (HAS), and dipeptidyl peptidase IV (DPP-IV) inhibitory potentials, as well as for their in vivo antidiabetic effects on high-sugar high-fat diet (HSHFD) + streptozotocin (STZ) induced diabetic rats (8-weeks study), by assessing fasting blood sugar, 1 h- and 2 h-oral glucose tolerance tests, serum insulin, homeostatic model assessment (HOMA) analyses, serum creatinine, urea, and blood urea nitrogen. Phytochemical analysis revealed that sumac extract had the highest total phenolic content, total flavonoid content, and total anthocyanin content followed by pomegranate peel and almond leaves. All extracts and fractions showed antioxidant (DPPH and FRAP) and enzyme (HAS and DPP-IV) inhibition activities and also suppressed STZ effects in diabetic mice by increasing superoxide dismutase, glutathione S-transferase, and insulin, as well as by decreasing HOMA2-IR, urea, and creatinine, with sumac extract showing benefits even when administered prior to STZ. In addition, in vivo results showed that sumac fruit extract significantly improved glycemic control by reducing fasting blood sugar, enhancing insulin secretion, and improving insulin resistance. These findings suggest that all tested extracts, particularly sumac, possess significant antioxidant, phytochemical, and antidiabetic potential.