Evaluation of the Antihyperglycemic Activity of Ethanolic Extracts of Syzygium tamilnadense in Nicotinamide–Streptozotocin-Induced Type 2 Diabetic Rats

Diabetes mellitus is a chronic metabolic disorder characterized by persistent hyperglycemia resulting from impaired insulin secretion, insulin resistance, or both. Prolonged hyperglycemia is associated with oxidative stress, dyslipidemia, and progressive damage to vital organs, highlighting the need for safer and more effective therapeutic agents. Syzygium tamilnadense Rathakr. & Chitra, an endemic medicinal species of the Western Ghats, India, has been traditionally used for various therapeutic purposes; however, its antidiabetic potential has not been scientifically validated. To the best of our knowledge, this is the first scientific exploration of its medicinal potential. The present study aimed to evaluate the antihyperglycemic, antioxidant, and organ-protective effects of the ethanolic extract of S . tamilnadense in nicotinamide–streptozotocin-induced type 2 diabetic rats. Experimental diabetes was induced using nicotinamide and streptozotocin, followed by oral administration of different doses of the ethanolic extract for four weeks. Fasting blood glucose, oral glucose tolerance, glycated hemoglobin (HbA1c), serum insulin, hepatic glycogen, lipid profile, antioxidant enzymes, hepatic and renal function biomarkers, and histopathological changes in pancreatic and hepatic tissues were evaluated. Treatment with S. tamilnadense significantly reduced fasting blood glucose and HbA1c levels, improved glucose tolerance, restored serum insulin and hepatic glycogen levels, normalized serum lipid profiles, and enhanced body weight compared with diabetic controls. The extract also improved endogenous antioxidant defense, attenuated oxidative stress, and significantly ameliorated hepatic and renal dysfunction. Histopathological examination further demonstrated marked regeneration of pancreatic β-cells and restoration of normal hepatic architecture in treated animals. The higher-dose treatment exhibited therapeutic efficacy comparable to the standard antidiabetic drug. These findings demonstrate that the ethanolic extract of S. tamilnadense possesses significant antihyperglycemic, antioxidant, hepatoprotective, and nephroprotective activities, suggesting its potential as a promising natural therapeutic candidate for the management of type 2 diabetes mellitus. Further studies are warranted to isolate the bioactive constituents and elucidate the underlying molecular mechanisms.