Rhinacanthus nasutus has traditionally been used in the treatment of various disorders including diabetes mellitus. Rhinacanthins-rich extract (RRE) is a semipurified R. nasutus leaf extract that contains 60% w/w of rhinacanthin-C (RC) obtained by a green extraction process. The purpose of this study was to investigate the anti-hyperglycemic and anti-hyperlipidemic activity of RRE (15 mg/kg equivalent to RC content) in comparison to its marker compound RC (15 mg/kg) and the standard drug glibenclamide (Glb) (600 μg/kg) in nicotinamide-streptozotocin induced diabetic rats for 28 days. In addition, the in silico pharmacokinetic and toxicity analysis of RC was also performed. RRE, RC and Glb significantly reduced the FBG, HbA1c and food/water intake while increasing the insulin level and body weight in diabetic rats without affecting the normal rats. The serum lipid, liver and kidney biomarkers were markedly normalized by RRE, RC and Glb in diabetic rats without affecting the normal rats. Moreover, the histopathology of the pancreas revealed that RRE, RC and Glb evidently restored the islets of Langerhans in diabetic rats. The overall results indicated that RRE has equivalent antidiabetic potential to that of RC. Moreover, the in silico pharmacokinetic and toxicity analysis predicts that RC is orally non-toxic, non-carcinogenic and non-mutagenic with a decent bioavailability. The undertaken study suggests that RRE could be used as an effective natural remedy in the treatment of diabetes.