Effect of madecassoside in reducing oxidative stress and blood glucose in streptozotocin-nicotinamide-induced diabetes in rats.

OBJECTIVES: Madecassoside (MAD) is a triterpenoid constituent of Centella asiatica (L.) Urb., an ethnomedical tropical plant, extracts of which were shown to reduce blood glucose in experimental diabetes. This study examines MAD for its anti-hyperglycaemic effects and tests the hypothesis that it reduces the blood glucose in experimentally induced diabetic rats by protecting the ß-cells. METHODS: Diabetes was induced using streptozotocin (60 mg/kg, i.v.) followed by nicotinamide (210 mg/kg, intraperitoneal (i.p.)). MAD (50 mg/kg) was administered orally for 4 weeks, commencing 15 days after induction of diabetes; resveratrol (10 mg/kg) was used as a positive control. Fasting blood glucose, plasma insulin, HbA1c, liver and lipid parameters were measured, along with antioxidant enzymes and malondialdehyde as an index of lipid peroxidation; histological and immunohistochemical studies were also undertaken. KEY FINDINGS: MAD normalized the elevated fasting blood glucose levels. This was associated with increased plasma insulin concentrations. MAD alleviated oxidative stress by improving enzymatic antioxidants and reducing lipid peroxidation. Histopathological examination showed significant recovery of islet structural degeneration and an increased area of islets. Immunohistochemical staining showed increased insulin content in islets of MAD-treated rats. CONCLUSIONS: The results demonstrate an antidiabetic effect of MAD associated with preservation of ß-cell structure and function.

The Protective Action of the Aqueous Extract of Auricularia polytricha in Paracetamol Induced Hepatotoxicity in Rats.

Natural antioxidant products are increasingly being used to treat various pathological liver injuries considering the role of oxidative stress in their pathogenesis. Auricularia polytricha has been used as food or medicine due to its antioxidant activity. The aim of the study was to evaluate the protective effect of the aqueous extract of the fruiting bodies of A. polytricha against paracetamol-induced liver toxicity in rats. Liver toxicity was induced in Sprague-Dawley rats by oral administration of 2g/kg paracetamol on the 15th day after the administration of aqueous extract and silymarin 100 mg/kg. Aqueous extract of A. polytricha was administered orally at 250 and 500 mg/kg doses, daily for a period of 14 days. Aspartate aminotransferase (AST), Alanine transaminase (ALT) and Alkaline phosphatase (ALP), Lactate dehydrogenase (LDH), Total bilirubin (TB), Total protein (TP), Triglycerides (TG) and cholesterol were measured to assess the effect of the extract on paracetamol-induced hepatic damage. The patent on Auricularia Polytricha (EP0413052A1) assisted in selecting the extraction procedure. The study also included histopathological examination of liver sections to assess hepatoprotective activity. Paracetamol significantly (P<0.001) increased the serum AST, ALT, ALP, LDH, TB, TG and cholesterol and decreased TP levels. Extract treatment significantly (P<0.001 to P<0.05) attenuated the paracetamol induced increase in AST, ALT, ALP, LDH, TB, TG and cholesterol and increased the diminished TP in a dose dependent manner. The standard drug, silymarin produced significant (P<0.001) decrease in AST, ALT, ALP, LDH, TB, TG and cholesterol and increase in TP. Histopathological examination of animals treated with paracetamol showed large areas of centrilobular necrosis with congestion and dilatation in both central and portal veins. These results indicate that the aqueous extract of A. polytricha has significant protective effect against paracetamol-induced liver toxicity in rats, due to its potent antioxidant activity.