Solanum torvum Swartz. fruit containing phenolic compounds shows antidiabetic and antioxidant effects in streptozotocin induced diabetic rats Gopalsamy Rajiv Gandhi, Savarimuthu Ignacimuthu ⇑ , Michael Gabriel Paulraj Division of Ethnopharmacology, Entomology Research Institute, Loyola College, Chennai 600 034, India article info Article history: Received 20 June 2011 Accepted 4 August 2011 Available online 10 August 2011 Keywords: Solanum torvum Phenolic compounds Diabetes Antioxidant Histology Immunohistochemical abstract In this study, quantification of phenolic compounds and the investigation of antidiabetic and antioxidant activities of the fruit of Solanum torvum Swartz. are described. S. torvum fruit methanol extract (STMe) was administered orally at a dose of 200 and 400 mg/kg/day to streptozotocin induced diabetic rats for 30 days. The levels of glucose, insulin, total protein, hemoglobin, glycated hemoglobin, liver glycogen and marker enzymes of carbohydrate metabolism, hepatic function and antioxidants were analyzed. High-performance liquid chromatography (HPLC) analysis revealed that STMe contained high levels of phenolic compounds, mainly rutin (1.36% w/w), caffeic acid (12.03% w/w), gallic acid (4.78% w/w) and catechin (0.46% w/w). STMe at 200 and 400 mg/kg reduced blood glucose level by 17.04% and 42.10%, respectively in diabetic rats. The levels and/or activities of other biochemical parameters were restored significantly compared to diabetic control rats due to treatment with fruit extract. Histology of liver and pancreas in STMe treated groups substantiated the cytoprotective action of the drug. Immunohisto- chemical observation of islets in extract treated diabetic rats showed apparent b-cells regeneration. These findings suggest that S. torvum fruit containing phenolic compounds has great potential as a natural source of antidiabetic and antioxidant drug. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Diabetes mellitus is a metabolic disorder characterized by hyperglycemia and disturbances of carbohydrate, protein and fat metabolisms, secondary to an absolute or relative lack of insulin (Fatima et al., 2010). The World Health Organization (WHO) esti- mates that more than 220 million people worldwide have diabetes, and this number is liable to double by 2030 (WHO, 2009). Hyper- glycemia is known to produce reactive oxygen species (ROS) which plays a central role in complications of diabetes (Dewanjee et al., 2009). Antioxidants play a major role in protection against molec- ular oxidative damage (Evans, 2007). In integration to oxidative stress, insulin action is also impaired in diabetes, which leads to in- creased hepatic glucose production. Due to the side effects of the existing synthetic drugs, plant derived food drugs are in great de- mand in industrially developed countries as alternative approach to treat diabetes. The World Health Organization (WHO) expert committee has recommended that plants possessing hypoglycemic activity may provide a utilizable source of new oral antidiabetic drug for the development of pharmaceutical entities, or may act as simple dietary adjuncts to the existing therapies (WHO, 1980). Solanum torvum Swartz. (Solanaceae) is a small tree of about 4m tall, evergreen, branched with white flowers. It occurs commonly in the moist farms of India and is widely distributed in Malaya, China, Philippines and Tropical America. S. torvum possesses antimicrobial, antiviral, immunosecretory, analgesic and anti-inflammatory activities (Mohan et al., 2009). The fruits of S. torvum are edible and commonly available in the markets. They are utilized as a vegetable and regarded as an essential ingre- dient in the South Indian population’s diet. It possesses antioxidant (Sivapriya and Srinivas, 2007), cardiovascular and anti-platelet aggregation activities (Mohan et al., 2009). Phenolic constituents reported from S. torvum fruit include rutin, caffeic acid, gallic acid, pyrogallol and catechin (Kusirisin et al., 2009). Quantitative analy- sis of phenolic compounds of S. torvum fruit and their contribution to the antidiabetic and antioxidant properties have not been stud- ied in detail to date. The present study endeavors to identify a novel source from tra- ditional Indian medicines and presents a comprehensive quantifi- cation of phenolic compounds using high-performance liquid chromatography (HPLC) along with evaluation of antidiabetic and 0278-6915/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.fct.2011.08.005 Abbreviations: STMe, Solanum torvum fruit methanol extract; STZ, streptozoto- cin; ELISA, enzyme linked immunosorbent assay; Hb, hemoglobin; HbA1c, glycated hemoglobin; AST, aspartate aminotransferase; ALT, alanine aminotransferase; ALP, alkaline phosphatase; TBARS, thiobarbituric acid reactive substances; SOD, super- oxide dismutase; CAT, catalase; GPx, glutathione peroxidase. ⇑ Corresponding author. Tel.: +91 44 28178348; fax: +91 44 28175566. E-mail address: entolc@hotmail.com (S. Ignacimuthu). Food and Chemical Toxicology 49 (2011) 2725–2733 Contents lists available at SciVerse ScienceDirect Food and Chemical Toxicology journal homepage: www.elsevier.com/locate/foodchemtox