<i>Pterocarpus soyauxii</i> Taub (<i>Papilionaceae</i>) Aqueous Stem Bark Extract Prevents Dexamethasone-induced Insulin Resistance and Oxidative Stress in Rat

Background: Data on safety degree and anti–type 1 diabetic effects of Pterocarpus soyauxii Taub are known, but not on type 2 diabetes yet. Objective: To evaluate preventive effects of P. soyauxii Taub aqueous stem bark extract on dexamethasone–induced insulin resistance and oxidative stress in rat. Materials and Methods: Glucose-overloaded normal Wistar rats were administered with P. soyauxii aqueous plant extract at various doses (38–300 mg.kg) in a single administration. Then, dexamethasone (Dex)–induced insulin-resistant rats received sub-chronic daily administration of the plant extract (38–300 mg/kg) for 21 days. Glibenclamide (10 mg/kg) and metformin (200 mg/kg) were respectively used in each test as standard treatments. Fasting blood glucose was followed for over 3 h in acute test. In sub-chronic test, body weight was followed weekly, glycemia before and at the end of treatment, and insulin sensitivity and serum and tissue biochemical parameters evaluated at the end of treatment. Results: Single administration of the plant extract significantly reduced (p<0.05) the serum glucose level increase of glucose-overloaded rats at lower doses, compared to hyperglycemic control. Its prolonged administration with dexamethasone in normal rats prevented insulin-resistance at all doses (p<0.001) similarly to metformin, without decreasing the body weight loss. The extract also prevented significantly (p<0.001) dexamethasone-induced increased serum creatinine, triglyceride, LDL-cholesterol, and transaminases, and decreased total proteins and HDL-cholesterol. Moreover, it improved significantly (p<0.05 – p<0.001) tissues oxidative stress parameters. Conclusion: P. soyauxii Taub aqueous stem bark extract can prevent the onset of type 2 diabetes.