|Year : 2011 | Volume
| Issue : 2 | Page : 189-193
Antihyperglycemic effect of Coscinium fenestratum and Catharanthus roseus in alloxan-induced diabetic rats
Shanmugam Manoharan, S Umadevi, S Jayanthi, N Baskaran
Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Annamalainagar - 608 002, Tamil Nadu, India
|Date of Submission||08-Mar-2011|
|Date of Acceptance||16-Apr-2011|
|Date of Web Publication||23-Aug-2011|
Department of Biochemistry and Biotechnology, Annamalai University, Faculty of Science, Annamalainagar - 608 002, Tamil Nadu
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction : Diabetes mellitus, the life-threatening endocrine disorder, affects 170 million people worldwide every year. Statistical projections about India suggest that 57 million Indians will be affected by diabetes mellitus by the year 2025, making the country with highest number of diabetics in the world. Alloxan-induced diabetes mellitus in experimental animals is commonly used to evaluate the antidiabetic effect of medicinal plants and their constituents. The present study has investigated the antidiabetic efficacy of ethanolic extract of Coscinium fenestratum stem and Catharanthus roseus leaves in alloxan-induced diabetic rats. Materials and Methods: Diabetes mellitus was induced in overnight fasted (>8 hours) Wistar rats by single intraperitoneal injection of freshly prepared alloxan monohydrate (150 mg/kg bw) solution in physiological saline. The mechanistic pathway for the antidiabetic potential of these plants was evaluated by analyzing the status of glucose, insulin, C-peptide, glycosylated hemoglobin, activities of carbohydrate-metabolizing enzymes, and glycogen content. The antidiabetic effect of these plant products was also compared with the standard reference drug, glibenclamide. Results: The study revealed that the ethanolic extract of C. fenestratum stem and C. roseus leaves have potent antidiabetic efficacy in alloxan-induced diabetic rats. The antidiabetic efficacy was also much comparable with that of glibenclamide. Conclusions: The present study concludes that the ethanolic extract of C. fenestratum stem and C. roseus leaves have potent antihyperglycemic effect in alloxan-induced diabetic rats. C. fenestratum and C. roseus could therefore be used as an alternative remedy for diabetes mellitus and its complications.
Keywords: Alloxan, Coscinium fenestratum, Catharanthus roseus, diabetes mellitus
|How to cite this article:|
Manoharan S, Umadevi S, Jayanthi S, Baskaran N. Antihyperglycemic effect of Coscinium fenestratum and Catharanthus roseus in alloxan-induced diabetic rats. Int J Nutr Pharmacol Neurol Dis 2011;1:189-93
|How to cite this URL:|
Manoharan S, Umadevi S, Jayanthi S, Baskaran N. Antihyperglycemic effect of Coscinium fenestratum and Catharanthus roseus in alloxan-induced diabetic rats. Int J Nutr Pharmacol Neurol Dis [serial online] 2011 [cited 2020 Feb 28];1:189-93. Available from: http://www.ijnpnd.com/text.asp?2011/1/2/189/84213
| Introduction|| |
Diabetes mellitus is characterized mainly by abnormalities in carbohydrate, lipids, and protein metabolism, due to defect in insulin secretion from pancreatic β-cells and/or insulin action. The number of people with type I (Insulin-dependent diabetes) and type II (non-insulin-dependent diabetes) diabetes mellitus are dramatically increasing worldwide. Currently, diabetes is the sixth leading cause of death in the United States, and diabetic patients have twice the death rate than people without diabetes. It has been estimated that major increase in diabetic population will occur in Asia-Pacific region. In India, more than 30 million people are currently affected by diabetes mellitus. ,
Alloxan is by far the most frequently used drug to induce diabetes mellitus in experimental animals and the same model has been used for the study of multiple aspects of diabetes mellitus. Alloxan induces diabetes mellitus when administered parenterally, intravenously, intraperitoneally, or subcutaneously in experimental animals. The dose of alloxan required to induce diabetes mellitus depends on the animal species, route of administration, and nutritional status. Alloxan causes severe necrosis of pancreatic β-cells with consequent lack of insulin secretion, possibly through generating excess reactive oxygen species. ,
Plant-based medicines continue to play an essential role in the primary healthcare of 80% of the World's underdeveloped and developed countries. Medicinal plants are used for the treatment of diabetes mellitus throughout the world, especially in countries where access to the conventional treatment of diabetes mellitus is inadequate. More than 150 medicinal plants are presently used in folk medicine and traditional healing systems in India for the treatment and management of diabetes mellitus and its complications. Medicinal plants exert their antidiabetic effect by correcting the defect in carbohydrate metabolism, maintaining integrity and function of β-cells, enhancing glucose uptake, and improving antioxidant defense mechanism. , Although several medicinal plants were reported to have antidiabetic efficacy in experimental animal models, a large number of medicinal plants still need scientific validity for their antidiabetic potential.
Coscinium fenestratum is popularly known as "Tree turmeric" in English. The stem of C. fenestratum is used by traditional practitioners of Indian traditional medicine for the treatment of several disorders including diabetes mellitus. The alcoholic extract of C. fenestratum stem has been reported to have antidiabetic and antioxidants properties. , Experimental studies have demonstrated its hypotensive and hepatoprotective action.  Catharanthus roseus (Vinca rosea) is popularly known as "Rose Periwinkle" in English. It is a perennial herb and grows to a height of 90 cm with a spread of 1 m. It is considered beneficial for its hypotensive, antispasmodic, and antitumor properties. Diverse pharmacological activities including anti-inflammatory, antibacterial, antitumor, antihyperglycemic, and antihypercholesterolemic effects have been reported. ,, Though very few experimental studies reported the antidiabetic potential of C. fenestratum and C. roseus in experimental diabetes, several biomarkers related to diabetes mellitus have not been assayed in these studies. The present study thus evaluated the antihyperglycemic effect of ethanolic extract of C. fenestratum stem and C. roseus leaves in alloxan-induced diabetic rats by analyzing the status of blood glucose, plasma insulin, C-peptide, glycosylated hemoglobin, activities of carbohydrate-metabolizing enzymes, and liver glycogen content.
| Materials and Methods|| |
Albino Wistar male rats 7 to 8 weeks old and weighing 150 to 200 g were used for the present study. The animals were obtained from Central Animal House, Rajah Muthiah Institute of Health Sciences, Annamalai University, India, and were maintained at 12 hours light and 12 hours dark cycles. The animals were randomized into control and experimental groups and were housed in polypropylene cages. Standard pellets obtained from Agro Corporation Private Limited, Bangalore, India, were used as a basal diet during the experimental period. The control and experimental animals were provided food and drinking water ad libitum.
Induction of diabetes mellitus
Diabetes mellitus was induced in overnight fasted (>8 hours) Wistar rats by single intraperitoneal injection of freshly prepared alloxan monohydrate (150 mg/kg bw) solution in physiological saline.  Animals that are having blood glucose level of >260 mg/dl were considered as diabetic and selected for the present study.
C. fenestratum stem and C. roseus leaves were collected in and around Chidambaram and were identified by Dr. K. Sivakumar, Reader, Department of Botany, Annamalai University, Annamalainagar. Voucher specimens were also deposited in the Department of Botany, Annamalai University, Annamalainagar.
Preparation of plant extracts
Ethanolic extract preparation
The ethanolic extract of C. fenestratum stem and C. roseus leaves was prepared separately according to the method of Hossain et al. (1992).  500 g of fresh plant products was dried, powdered, and then soaked in 1 500 ml of 95% of ethanol overnight. After filtration, the residue obtained was again resuspended in equal volume of 95% ethanol for 48 hours and filtered again. The above two filtrates were mixed and the solvent was evaporated in a rotavapor at 40°C to 50°C under reduced pressure. The yield of the ethanolic residual extract of C. fenestratum stem and C. roseus leaves are 16% and 14%, respectively. The ethanolic extract of the plant products was suspended in 2.0 ml distilled water and was orally administered to the animals by gastric intubation using a force-feeding needle during the experimental period.
The Institutional animal ethical committee (Registration number 160/1999/CPCSFA), Annamalai University, Annamalainagar, approved the experimental design. A total number of 42 rats were divided into seven groups and each group contained six rats.
Group I - Rats served as untreated control rats.
Group II - Rats were treated with single intraperitoneal injection of alloxan (150 mg/kg bw)
Group III - Diabetic rats were orally administered with ethanolic extract of C. fenestratum stem (300 mg/kg bw) daily for 45 days.
Group IV - Diabetic rats were orally administered with ethanolic extract of C. roseus leaves (300 mg/kg bw) daily for 45 days.
Group V - Diabetic rats were orally administered with glibenclamide (600 μg/kg bw) daily for 45 days.
Group VI - Rats were orally administered with ethanolic extract of C. fenestratum stem (300 mg/kg bw) alone daily for 45 days.
Group VII - Rats were orally administered with ethanolic extract of C. roseus leaves (300 mg/kg bw) alone daily for 45 days.
Biochemical studies were conducted in blood, plasma, and liver of control and experimental rats in each group. Plasma was separated from heparinized blood by centrifugation at 3 000 rpm for 15 minutes. Liver samples from control and experimental rats were weighed and homogenized using appropriate buffer in an all-glass homogenizer with Teflon pestle and then used for biochemical estimations.
Blood glucose was determined by the method of Sasaki et al. (1972)  using O-toluidine reagent. Total hemoglobin and glycosylated hemoglobin were measured by the method of Drabkin and Austin (1932)  and Sudhakar Nayak and Pattabiraman (1981)  , respectively. Plasma insulin was estimated by ELISA method using Boehinger Mannheim GmbH Kit.  Plasma C-peptide was estimated by Enzyme linked immunosorbent assay (ELISA) technique by a commercial kit.  Liver glycogen content was measured by the method of Morales et al. (1973).  The protein content was estimated by the method of Lowry et al. (1951).  The activities of hexokinase, glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, fructose 1,6-bisphosphatase, and glycogen phosphorylase were estimated according to the methods of Brandstrup et al. (1957),  Koide and Oda (1959),  Ellis and Kirkman (1961),  Gancedo and Gancedo (1971)  , and Shull et al. (1956),  respectively.
| Results|| |
The status of blood glucose, plasma insulin, C-peptide, glycosylated hemoglobin, and liver glycogen content in control and experimental animals in each group is shown in [Table 1]. Blood glucose and glycosylated hemoglobin levels were significantly increased, whereas plasma insulin, C-peptide, total hemoglobin, and liver glycogen were decreased in alloxan-induced diabetic rats (group II) as compared with control rats (group I). Treatment of alloxan-induced diabetic rats with the ethanolic extract of C. fenestratum stem and C. roseus leaves for 45 days brought back the status of above-mentioned biochemical parameters to near-normal range. The effect of ethanolic extract of C. fenestratum stem and C. roseus leaves were also much comparable with that of glibenclamide. No significant differences were observed between control animals and plant extract alone-treated animals.
The activities of carbohydrate-metabolizing enzymes (hexokinase, glucose-6-phosphate dehydrogenase, glucose-6-phosphatase, fructose-1,6-bisphosphatase, and glycogen phosphorylase) in liver of control and experimental animals in each group is shown in [Table 2]. Glucose-6- phosphatase, glycogen phosphorylase, and fructose-1,6-bisphosphatase activities were significantly increased, whereas the activities of hexokinase and glucose-6-phosphate dehydrogenase were decreased in diabetic rats as compared with control rats. However, treatment of alloxan-induced diabetic rats with the ethanolic extract of C. fenestratum stem and C. roseus leaves for 45 days brought back the activities of carbohydrate-metabolizing enzymes to near-normal range in the liver. The effect of ethanolic extract of C. fenestratum stem and C. roseus leaves were also much comparable with that of glibenclamide. No significant differences were observed between control animals and plant extract alone-treated animals.
|Table 1: Status of blood glucose, plasma insulin, C-peptide, total and glycosylated hemoglobin, and liver glycogen content in control and experimental rats in each group|
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|Table 2: Activities of liver carbohydrate-metabolizing enzymes in control and experimental rats in each group|
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| Discussion|| |
Glycosylated hemoglobin is now considered as the most reliable marker of glycemic control in diabetes mellitus. Administration of C-peptide to diabetic patients or diabetic animals has been shown to increase glucose uptake in skeletal muscle.  The observed increase in glycosylated hemoglobin and decrease in total hemoglobin and C-peptide in diabetic rats indicate poor glycemic control mechanism.
Oral administration of the ethanolic extract of C. fenestratum stem and C. roseus leaves to diabetic rats for 45 days brought back the status of blood glucose, total and glycosylated hemoglobin, plasma insulin, C-peptide, and liver glycogen content to near-normal range. The present study thus suggests that the ethanolic extract of C. fenestratum stem and C. roseus leaves improved the glycemic control mechanism by stimulating insulin secretion from surviving pancreatic β-cells as well as enhanced the utilization of glucose by hepatic and extrahepatic tissues of diabetic rats. Phytochemical examination of C. fenestratum and C. roseus revealed the presence of antidiabetic principles such as alkaloids, flavonoids, flavones, and glycosides. , The antihyperglycemic effect of these plant products could also be due to the presence of such active principles and their synergistic effects.
Liver has an important function in maintaining blood glucose homeostasis and the hormone insulin regulates the glucose metabolism in the liver.  Decrease in hexokinase activity and increase in glycogen phosphorylase activity could be responsible for the depletion of liver glycogen in diabetic rats. Increase in glucose-6-phosphatase, glycogen phosphorylase, and fructose-1,6-bisphosphatase activities and decrease in glucose-6-phosphate dehydrogenase and hexokinase activities as well as liver glycogen content in diabetic rats could be due to insulin insufficiency or defect in insulin action. Treatment of alloxan-induced diabetic rats with the ethanolic extract of C. fenestratum stem and C. roseus leaves brought back the status of carbohydrate-metabolizing enzymes and liver glycogen content to near-normal range. The results thus suggest that the plant extract might have corrected the defect in carbohydrate metabolism occurred during diabetes mellitus, as evidenced by increased plasma insulin, C-peptide, and liver glycogen content and decrease in blood glucose level after treatment with the plant extract.
The antidiabetic effect of the ethanolic extract of C. fenestratum stem and C. roseus leaves in diabetic rats was much comparable with that of the reference drug, glibenclamide. The investigated medicinal plants could therefore be used as an alternative remedy for diabetes mellitus and its complications.
| Conclusions|| |
The present study concludes that the ethanolic extract of C. fenestratum stem and C. roseus leaves have potent antihyperglycemic effect in alloxan-induced diabetic rats. The present investigation has also opened avenues for further research, especially with reference to the development of potent phytomedicine for diabetes mellitus from these traditionally used antidiabetic medicinal plants.
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[Table 1], [Table 2]