Plant material The root of this plant was collected from Rajshahi, Bangladesh, during the month of April 2010 and authenticated by expert Mr. Md. Arshed Hossain, Department of Botany, Rajshahi University. Voucher specimens, collection # 38, dated 10/30/2009 for P. pterocarpum kept in the Department of Botany, Rajshahi University, Rajshahi-6205, Bangladesh.
Preparation of extract Dried root of P. pterocarpum was pulverized in a ground mill. 100 g of powder was extracted three times by sonication for 30 min with methanol:ethyl acetate in the ratio of 1:9 (1000 ml) and then filtered. Here methanol:ethyl acetate in the ratio of 1:9 was used as a solvent to extract medium polar compounds from the plant part which are most often physiologically active. On the other hand, this solvent system does not allow the extraction of highly polar compounds like glycosydic glucose that are physiologically inactive and hence decrease the unwanted compounds in the test extract. Filtrate was concentrated by vacuum evaporator and dried. The extract was then preserved in the refrigerator for the experimental use.
Animals Male Swiss Albino mice (20 to 25 g) were collected from International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR, B) and housed in polypropylene cages under controlled conditions. The animals were exposed to alternative 12 h light and dark cycle. Animals were allowed free access to drinking water and pellet diet, collected from ICDDR, B; Dhaka. Mice were acclimatized for 7 days. All animal experiments were performed in accordance with NIH guidelines. The study protocol was approved by the animal Ethics Committee of the Institution.
Drugs Alloxan was purchased from Sisco Research Laboratories Pvt. Ltd. Mumbai, India and used for the induction of diabetes. The active drug, Metformin hydrochloride was collected from Square Pharmaceuticals Ltd., Pabna plant, Bangladesh. All other chemicals used were of analytical grade.
Preparation of dose Diabetes was induced with a single dose of freshly prepared alloxan (80 mg/kg b. w., i.p.) in sterile saline water. Two doses (200 and 300 mg/kg b. w.) of extract of P. pterocarpum root were used for testing antidiabetic activity and extract was administered intraperitoneally after dissolving in dimethyl sulfoxide (DMSO) vehicle. Standard drug metformin was injected in the same route at the dose of 150 mg/ kg b. w.
Effect of extract on glucose induced hyperglycemic mice For oral glucose tolerance test (OGTT), 25 more mice were divided into five groups (n = 5) from Group I to Group V. Group I and Group II were selected for normal control and diabetic control group respectively. After overnight fasting, a baseline blood glucose level (BGL) was estimated (0 min). Without delay, a glucose solution (2 g/kg b. w.) was administered by gavages from Group II to Group V. At the same time Group III received standard drug and the test groups (Group IV and Group V) received 200 and 300 mg/kg of plant extracts intraperitoneally. Five more readings were taken at 30, 60, 90, 150, 270 min after glucose and test sample administration.
Statistical analysis The experimental data were presented as the means ± SEM. The differences between the groups were considered as significant at *P<0.05 by student’s T-test and Tukey’s test using GraphPad Prism version 4.00 for Windows (GraphPad Software, San Diego, CA, USA, www.graphpad.com).