2. Materials and Methods
2.1. Collection of Plant Material. The fresh leaves of R. nasu- tus were collected from Tirumala Hills, Tirupati, Chittoo
districts of Andhra Pradesh from July to October 2009. The plant specimen was verified to be the correct species by Dr. Madhava Setty, a botanist from the Department of Botany, S. V. University, Tirupati, India.
2.2. Preparation of the Extract. Fresh leaves of R. nasutus (500 g) were shade-dried and milled into fine powder using a mechanical grinder (TTK Prestige, Chennai, India). The powdered plant material was macerated and shaken in methanol using a bath shaker (Thermo Scientific, Mumbai, India) for 48 h. The extract was then filtered with filter paper (Whatman no. 1) and evaporated to dryness under a vacuum with reduced pressure using a rotary evaporator at 40∘C. The concentrate was then placed on aluminum foil before freeze drying. The residual extract was dissolved in 1 mL of sterile water before use.
2.3. Chemicals. Streptozotocin (STZ) was purchased from Sigma (USA). All other chemicals and reagents used in this study were of analytical grade. Glibenclamide (Sugatrol, Hyderabad, India) was purchased from a local drug store.
2.4. Experimental Design. Adult male Wistar rats weighing between 150 and 180 g were obtained from Sri Venkateswara Enterprises, Bangalore, India. They were individually housed in clean, sterile polypropylene cages under standard con- ditions (12 h light/dark cycles) with free access to standard chow (Hindustan Lever Ltd., Bangalore, India) and water ad libitum. Before the commencement of experiments, the animals were allowed to acclimatize to laboratory condi- tions for one week. The animal experiments were designed and performed in accordance with the ethical standards approved by the local Ministry of Social Justices and Empowerment, Government of India, and the Institu- tional Animal Ethics Committee Guidelines (Resolution no. 05/(i)/a/CPCSEA/IAEC/SVU/MDN-PVR/dt.13.09.2010).
2.5. Induction of Experimental Diabetes. Diabetes was induced by a single intraperitoneal injection of a freshly prepared STZ solution (Sigma, no. 242-646-8) (50mg/kg in citrate buffer 0.01M, pH 4.5) to overnight-fasted rats. Diabetes was confirmed by the presence of polydipsia and polyurea as well as by measuring the nonfasting plasma glucose levels 48h after STZ injection. Only animals that were confirmed to have blood glucose levels greater than 250 mg/dL were included in the study. All the animals were allowed free access to tap water and pellet chow in accordance with the guidelines of the Institute Animal Ethics committee.
The rats were divided into five groups of six animals each as follows.
2.6. Acute Toxicity Test. R. nasutus (50–250mg/kg body weight) was orally administered to rats for acute toxicity stud- ies. Each group was observed individually for signs of toxicity and behavioral changes such as hyperactivity, grooming, con- vulsions, sedation, or hypothermia. These observations began 1 h after dosing and were continued at least once daily for 14 days. The mortality rate was also calculated.
2.7. Biochemical Measurements. At the end of the study (30 days), after an overnight fasting, the animals were sacrificed by cervical dislocation following anesthesia using isoflurane. The liver tissue was excised and washed with ice-cold saline and was immediately immersed in liquid nitrogen and stored at −80∘C for further biochemical analysis. Then, the measure- ments of liver enzyme activity and biochemical assays were performed.
AST and ALT activities were assayed using the method of Reitman and Frankel [28]. The total carbohydrate content was estimated based on the method established by Carroll et al. [29]. Glycogen content was determined as described by Saifter et al. [30]. The protein content was estimated by the method of Lowry et al. [31] with slight modifications. All enzymatic assays in this study were performed using crude liver homogenate.
2.8. Statistical Analysis. The results were expressed as the mean ± SD (