International Journal of Drug Development and Research

Keywords

Alocasia indica, diabetes mellitus, hyperlipidemia Streptozotocin, Glibenclamide.

Introduction

Diabetes mellitus is characterized by hyperglycemia with disturbances of carbohydrate, lipid & protein metabolism. Obesity & lack of exercise plays an important role in diabetes.[1] According to world health organisation projections, around 3.2 million deaths every year worldwide are attributable to complications of diabetes, characterized by retinopathy, nephropathy, neuropathy, microangiopathy & diabetic ketoacidosis which leads to six deaths every minute.[2] Increased production of superoxides & lowered antioxidant enzyme activities compromising with body antioxidants defence systems in hyperglycemia is associated with the pathogenesis of diabetic dyslipidaemia, micro & macro vascular complications.[3] Currently available oral hypoglycaemic agents (sulphonylureas, biguanides etc.) have side effects and failure of response after prolonged use.[4] Though different type of hypoglycaemic agents are available along with insulin for the treatment of diabetes, there is an increase demand by patients to use natural products with antidiabetic activity. Plant based medicines are gaining prominence in the treatment of metabolic diseases like diabetes.[5] Many flavonoids containing plants serves as a hidden wealth of potentially useful natural product for diabetes control.[6]

Alocasia indica Schott. is a perennial herb with stout rootstock, found tropical and sub tropical regions of India. The Alocasia indica Schott. (Family- Araceae) commonly known as Giant Taro is a perennial herb found throughout greater part of India.[7] According to ayurvedic literature, different parts of this plant are traditionally used as hepatoprotective, antioxidant, analgesic, antiarthritic, antiinflammatory, antitumour & antipyretic.[8] It is also reported to use in the treatment of diabetes mellitus & piles.[9] Alcoholic extract of leaves were evaluated for antimicrobial[10], antidiarrhoeal[11], antioxidant[12], anti-inflammatory[12], & anthelminitic[13] properties. Seeds extract is reported for its antifungal activity. [14] Literature survey revealed that the plant contains flavonoids, alkaloids, cyanogenetic glycosides, steroids, gallic acid, succinic acid, ascorbic acid, amino acids, oxalic acid, [8] & alocasin. [15] It is evident that the plant has great potentials in treating various diseases where free radicals have been reported to the major factors contributing to the disorders. However literature indicates that there is no scientific data to support antidiabetic & hypolipidemic potential of leaves of Alocasia indica Schott. Thus, the present study investigates the action of alcoholic extract of leaves of Alocasia indica Schott. to ascertain the scientific basis for the use of this plant in the treatment of diabetes & hyperlipidemia.

MATERIALS & METHODS

Plant material

Fresh leaves of Alocasia indica Schott. were collected in the month of January 2011, from local areas of Ibrahimpatnam, Hyderabad and authenticated by Prof. B. Amarendhar Reddy, Sai Gouthami College, Ibrahimpatnam, R.R.Dist, A.P, India.

Preparation of test extracts

The plant material was dried under shade at room temperature and powdered to coarse particles. The powdered plant material was defatted with petroleum ether (60-80°C) in a Soxhlet extraction apparatus and marc was extracted with ethanol. The solvent was removed using rotary flash evaporator to get a residue of ethanol extract which was dried to constant weight under vacuum and stored in desiccator till further use.

Preliminary Phytochemical screening

Preliminary Phytochemical screening was carried out on alcoholic extract of Alocasia indica leaves for qualitative determination of phytoconstituents. [16]

Animals

Wistar rats of either sex, weighing between 150 -200 gm were used for the study. Animals were kept in standard polypropylene cage & maintained under standard laboratory conditions of temperature (25±1ºC), relative humidity (50±15%), 12 hour light dark cycles, standard diet & water ad libitum. All studies were conducted according to Institutional Animal Ethical Committee.

Chemicals

Streptozotocin was purchased from Sigma-Aldrich, India. The streptozotocin solution was prepared by freshly dissolving in citrate buffer (0.01 M, pH 4.5). Total cholesterol, high density lipoprotein (HDL)- cholesterol and triglyceride (TC) standard kits were purchased from Erba Diagnostics Mannheim Gambh, Germany. All reagents used in study were analytical grade.

Acute toxicity studies

The acute oral toxicity study was carried out as per the guidelines set by Organization for Economic Cooperation and Development (OECD), the study was approved by the Institutional Animal Ethics Committee (IAEC). No mortality and no signs of toxicity were found even after administration of a limit dose of 2000 mg kg-1 b.w of extract; hence 1/10th of the dose was taken as effective dose. Two doses, 200 and 400 mg kg-1 were selected for the present study to evaluate antidiabetic and hypolipidemic activity. [17]

Induction of diabetes

The streptozotocin diabetic rat model was performed as per the method described by Kandur & Goyal. Rats were injected intraperitoneally with 60 mg kg-1 body weight. Streptozotocin dissolved in 0.1 M cold citrate buffer (pH 4.5). Fourty eight hours after streptozotocin administration, blood samples were drawn by retro orbital puncture and glucose levels were determined to confirm diabetes. The diabetic rats exhibiting blood glucose levels in the range 275 & 300mg/100ml were selected for the studies. [18]

Experimental design

All the diabetic animals were randomly divided into five groups with six animals each & treated once a day for 21 days as follows. Group I (normal control) received only vehicle (1% w/v CMC in water). Group II (diabetic control) received vehicle (1% w/v CMC in water). Group III & Group IV (extract treated) received alcoholic extract of Alocasia indica leaves at dose of 200 & 400 mg kg-1 b.w. for 21 days. Group V (standard) treated with Glibenclamide 10 mg kg-1 b.w. for 21 days. [19]

Estimation of blood glucose level

Blood glucose levels & body weights were measured on day 1, 7, 14 & 21 of the study. Finally on day 21, blood was drawn by retro-orbital puncture technique. Blood samples were collected, allowed to clot and then centrifuged at 2000 rpm for 10 minutes to obtain serum. [20] Blood glucose was estimated by single touch glucometer (one touch ultra, Johnson & Johnson Ltd.)

Biochemical analysis

All lipid profiles i.e. total cholesterol, triglycerides & HDL-cholesterol were estimated using commercial diagnostic kits. All estimations were done according to the kit manufacturer’s instructions.

Statistical Analysis

The results were expressed as mean ± SEM. The results obtained from the present study were analysed using One-way ANOVA followed by Dunnett’s multiple comparison test. Data was computed for statistical analysis using Graph Pad Prism software. Differences between the data were considered significant at P<0.05

RESULTS

Preliminary Phytochemical screening indicated the presence of phenolic compounds (flavonoids) & steroids.

Effect on body weight:

The body weight of diabetic control group significantly decreased compared with normal controls. During regular observation of test extract treated diabetic rats there were significant (P<0.05) weight gains on 21st day relative to initial day as shown in table 1.

Effect on blood glucose level:

There was a significant increase (P<0.05) in blood glucose level in diabetic rats when compared with normal control due to streptozotocin injection. In the study, daily oral administration of the test extracts for the period of 3 weeks led to a dose dependent fall in blood glucose levels & showed significant reduction (P<0.05) in blood glucose levels compared to diabetic control. At the end of experiment blood glucose level was 131.98±0.98 & 105.26±0.87 mg/dl at the doses of 200 & 400 mg kg-1 of alcoholic extract of Alocasia indica leaves respectively. The antidiabetic effect of test extract on blood glucose level in diabetic rats is shown in Table 2.

Effect on Lipid profile level

The results obtained reveal significant increased in serum cholesterol, triglycerides & decreased serum HDL-cholesterol in diabetic control group over a period of 21 days. The hypolipidemic profile observed with test extract was similar to that seen with reference drug, glibenclamide. The 21 days treatment with test extracts showed a significant reduction in cholesterol & triglycerides levels when compared with the diabetic control (P<0.05). HDL- cholesterol was significantly improved by treatment of extract. The reference drug at a dose of 10 mg kg-1 for 21 days also lowered serum cholesterols and triglycerides significantly & HDL- cholesterol was effectively increased than the normal group (Table 3).

DISCUSSION

Pancreas is the primary organ involved in sensing the organism’s dietary and energetic states via glucose concentration in the blood and in response to elevated blood glucose; insulin is secreted.[21] streptozotocin causes a massive reduction in insulin release by the destruction of N-cells of the islets of Langerhans. An insufficient release of insulin, that leads high blood glucose namely hyperglycemia. [22] Insulin deficiency leads to various metabolic alterations in the animals, viz. increased blood glucose, increased cholesterol and transaminases.[23] The fundamental mechanism underlying hyperglycemia in diabetes mellitus involves overproduction (excessive hepatic glycogenolysis and gluconeogenesis) and decreased utilization of glucose by the tissues.[24] In the present study the antidiabetic & hypolipidemic activity of alcoholic extract of Alocasia indica leaves was evaluated in streptozotocin induced diabetic rats. The activity exhibited was compared with the standard antidiabetic drug (Glibenclamide). Daily treatment with the test extracts for a period of 21 days showed a significant decrease (P<0.05) in the serum glucose level at 7th, 14th and 21st days and maximum reduction occurred at 21st day in diabetic rats. It is evident from these investigations that the alcoholic extract is effective in maintaining the serum glucose levels in streptozotocin induced diabetic rats. During the 21-day experimental period the body weight was reduced in diabetic rats, whereas there was a significant (P<0.05) gain of body weight in treated rats. The administration of test extracts check the loss in body weight and restored these levels significantly (P<0.05) towards normal. The ability of the test extract to restore body weight seems to be a result of its ability to reduce diabetes by increased glucose metabolism. [25] This may also be due to the protective effect of the extract in controlling muscle wasting i.e. reversal of gluconeogenesis. It is well known that in uncontrolled diabetes mellitus, there will be an increase in total cholesterol, triglycerides with decrease in HDL-cholesterol & contributes to coronary artery disease.[26] In the present study the total cholesterol & triglycerides were increased significantly (P<0.05) in diabetic control groups and these were significantly (P<0.05) reduced in 21 days treatment with test extract as well as the HDLcholesterol level was significantly increased (P<0.05). The hypolipidemic effect may be due to inhibition of fatty acid synthesis.[27] In normal metabolism insulin activates the enzyme lipoprotein lipase and hydrolyses triglycerides and the deficiency in insulin results in inactivation of these enzymes thereby causing hypertriglyceridemia. The significant reduction of serum lipid levels in diabetic rats after treatment with alcoholic extract of Alocasia indica may be directly attributed to improvements in insulin levels or the extract may inhibit the pathway of cholesterol synthesis.[28]

Insulin is the main regulator for glycogenesis in liver. The improvement of liver function and subsequent increase in uptake of blood glucose and its utilization may be another mechanism of action of the extract. Other possible mechanism includes the stimulation of N-cells and subsequent release of insulin and activation of the insulin receptors. Estimation of insulin level and insulin receptor may give more insight into the mechanism of the antidiabetic activity exhibited by the extract. The studies also reveal that steroids and flavonoids present in the plant extract known to possess antidiabetic activity.[29] In the present investigation also the observed antidiabetic potential of test extract may be due to presence of similar phytoconstitutes.

CONCLUSION

On the basis of the aforementioned results, we concluded that alcoholic extract of Alocasia indica leaves has beneficial effects on serum glucose levels as well as improving hypercholesterolemia and other metabolic aberrations as it lowers blood glucose level in diabetic rats. Therefore, Alocasia indica Schott. is considered to be effective and alternative treatment for diabetes. Further phytochemical & pharmacological investigations will clearly elucidate the specific phytoconstituents & mechanism of action responsible for such an effect and will be helpful in projecting this plant as a therapeutic target in diabetes research.

Conflict of Interest

NIL

Source of Support

NONE

Tables at a glance

Table 1 Table 2 Table 3

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