To chemically characterise a phenolic-rich aqueous extract of Connarus suberosus Planch. (Connaraceae) leaves and evaluate its antihyperglycaemic, hypolipidaemic, antioxidant, and organ-protective effects in streptozotocin (STZ)-induced diabetic rats.

An infusion-type aqueous extract was characterized by UHPLC–HRMS, and total phenolic content was determined using the Folin–Ciocalteu assay. Male Wistar rats with STZ-induced diabetes received oral treatment for 28 days with C. suberosus extract (150 mg/kg/day), glibenclamide (10 mg/kg/day), or vehicle. Fasting blood glucose, body weight, serum lipid profile, hepatic and renal biochemical markers, oxidative stress parameters (TBARS, TEAC, and nitric oxide), and qualitative histopathological changes in the liver and pancreas were evaluated.

UHPLC–HRMS analysis revealed a phenolic-rich extract containing quercetin, quercitrin, kaempferol-3-O-rutinoside, olivil 4′-O-glucoside, and procyanidin A1 as major constituents. Treatment with C. suberosus significantly reduced fasting blood glucose (approximately 70% compared with untreated diabetic rats), normalized serum triglyceride levels, attenuated increases in AST activity, and preserved serum creatinine and urea within values comparable to non-diabetic controls. The extract also reduced nitric oxide overproduction, partially restored total antioxidant capacity, and was associated with qualitative preservation of pancreatic islet architecture and hepatic morphology.

The phenolic-rich aqueous extract of C. suberosus attenuated hyperglycaemia and improved several biochemical and histopathological alterations associated with STZ-induced diabetes. These findings support its potential as a source of bioactive compounds with antihyperglycaemic and organ-protective properties. However, because insulin secretion, insulin sensitivity, long-term glycaemic control, and molecular signaling pathways were not investigated, the underlying mechanisms remain to be elucidated in future studies.