Hypoglycemic and Hypolipidemic Effects of Watermelon ( Citrullus Vulgaris ) Seed Kernels on Male Albino Rats

The current investigation was planned to assess the hypoglycemic and hypolipidemic efficiency of watermelon seeds on male albino rats. Eight male albino rats weighing between 105-150g were randomly selected for the present experiment and were placed into two equal groups (n=4) designated as control and treated group. The control group received normal stock diet (20% protein, 5 % fat, 60 % carbohydrate). The treated group received a modified diet (90g Stock diet excluding groundnut oil + 9g watermelon seed kernel + 1g sugar). Percentages of protein, fat and carbohydrate in the modified diet were kept same as that of the stock diet. All animals were given water ad libitum. Rats were weighed at weekly intervals. After 28 days rats were anesthetized using chloroform anesthesia and blood samples were collected via cardiac puncture and serum was obtained for evaluation of some biochemical parameters. Result showed that serum glucose, triglyceride (TG) and very low density lipoprotein (VLDL) of the treated group were decreased significantly (p < 0.01, p < 0.05 and p < 0.05 respectively) compared to that of the control group. Liver glycogen, serum total cholesterol, low density lipoprotein (LDL) and AI (Atherogenic Index) were decreased (non-significant) whereas high density lipoprotein (HDL) increased (non-significant) in the treated group. Current Research in nutrition and Food Science Journal Website:www.foodandnutritionjournal.org ISSN: 2347-467X, Vol. 5, No. (3) 2017, Pg. 368-373 ContACt Reetapa Biswas biswasreetapa@gmail.com Department of Home Science, Food and Nutrition Division, University

introduction Dual burden of malnutrition exists in the Indian society.According to NFHS 3 (2005-2006) diabetes is highly prevalent in urban areas (1.374% women and 1.383% men) than in rural areas (0.641% women and 0.86% men).World Health Report 2002 speculated that cardiovascular diseases (CVDs) will be the largest cause of death and disability by 2020 in India.On the other hand the magnitude of the problem found to be even more serious while giving a glimpse on national nutrition data.According to NFHS 3 (2005-2006) 40.4% children of below 3 years were underweight.Among the adults 36% of women and 34% of men are undernourished, with a BMI less than 18.5.This indicates an alarming situation of nutritional deficiency.In this present scenario recently more attention has been focused to recover valuable components from neglected food parts (food "losses", "wastes", "by-products") and reintroduce them inside the food chain.Watermelon (Citrullus vulgaris) seed, whose cultivar name is Sugar baby is one of such component.

Sample description
Watermelon seeds are easily available during summer season.Though it is not an oilseed but researches have shown that these seeds contain about 52.6% oil 1 , so these are good source of energy (628k.cal).C. Gopalan has listed watermelon seeds under nuts and oilseeds.C. vulgaris seed kernel contains highest amount of protein (34.1g/100g) compared to that of any other oilseeds.It also contains considerable amount of Arginine (900 mg/g of N) and branched chain amino acids (leucine, isoleucine and valine) 1 .
Inspite of being highly nutritious and having some known medicinal values, these seeds have still not recognized and are less acceptable amongst the people as compared to other oilseeds.Previous work showed that watermelon seed kernel promotes growth due to the presence of good quality protein which was evidenced by significantly increased Protein Efficiency Ratio (PER) among the male albino rats, and therefore may be useful in prevention and treatment of Protein Energy Malnutrition (PEM) 2 .The nutritional importance of the seed kernels of C. vulgaris have been found in some discrete studies, but little work has been done on the effect of the seeds of C. vulgaris on different bodily systems of animals or humans.Hence the objectives of the present research are to: • prepare a modified diet of male albino rats by adding watermelon seed kernel to the stock diet instead of groundnut oil so that its protein, fat, carbohydrate and calorie content would be same as that of the stock diet.• study the effects of C. vulgaris seed kernels on serum glucose and liver glycogen of male albino rats.• study the effects of C. vulgaris seed kernels on serum lipid profile of male albino rats.

Collection of Seeds and preparation of Sample
Watermelons of specific species (C.vulgaris) were purchased during summer season (April to June) from local markets of Chetla and Rashbehari, Kolkata.The watermelons were cut with a clean, sharp knife, and the seeds were handpicked from them, washed thoroughly with tap water and then dried in shade at room temperature.Then the seeds were screened to remove the bad and immature ones.Finally the seeds were dehusked in a decorticator and the seed kernels were separated from the seed coat.The seed kernels were grounded in a mixer grinder and preserved in a dry, clean container for preparing the experimental diet.

Animal Experiment
Eight male albino rats weighing between 105-150g were used for the experiment with due approval of the Institutional Animal Ethical Committee (IAEC).They were assigned into 2 groups, (n = 4), labeled as control and treated group.The control group received normal stock diet (20% protein, 5 % fat, 60 % carbohydrate) 3 .The experimental group received a modified diet (90g Stock diet excluding groundnut oil + 9g watermelon seed kernel + 1g sugar) and the percentages of protein, fat and carbohydrate were kept almost same as that of the stock diet.All the animals were given water ad libitum.The detail composition of the stock and the modified diet were as follows- The total experimental period was 28 days during which the rats were weighed at weekly intervals.After 28 days of feeding with the modified diet, the animals were anesthetized using chloroform anesthesia following ethical procedures.Blood samples were then collected via cardiac puncture and serum was separated for the analysis of glucose and lipid profile.Serum glucose, liver glycogen and lipid profile were analyzed by the following methods- liver glycogen was estimated by the standard method described in the book named "A Manual of laboratory techniques" of iCMR 3 The liver was taken out rapidly from the animal & the excess blood was removed by blotting between folds of filter paper.Immediately 1g of liver was cut and weighed in digital balance and put into test tubes containing 2 ml of 30% KOH with a tissue concentration 2 ml/g of liver.After that the tissue of different rats were digested in a boiling water bath for 1hour and then cooled in ice cold water.4 ml of 95% ethanol were then added & the mixture was heated just to boiling, taking care so that no spurting occurs during the process.It was then left to stand for overnight in the refrigerator.Next day the tubes were centrifuged and the supernatant was discarded.
The precipitate was dissolved in 10 ml of warm water.

Results and discussions
Serum glucose level decreased significantly (p < 0.01) among the treated group of animals than that of the control group but there was no significant difference in the liver glycogen content of the two groups of rats (Table -3).Type of fat intake, may be linked to insulin resistance, which can increase risk of developing type 2 diabetes and impaired postprandial lipid metabolism 9,10 .Previous studies showed that C. vulgaris seed kernel contained branched chain amino acids (BCAAs) i.e. leucine (400 mg/g of N), isoleucine (310mg/g of N) and valine  12 .It has also been showed that the post-prandial blood sugar levels were decreased in the vitamin E supplemented patients of the type I DM patients over 24 months and also in the type II DM patients.This decline was statistically significant only at the end of 24 months 13 .Therefore, presence of substantial amounts of BCAAs and Vitamin E are probably the causative agents of hypoglycemic function of this seed.
The results obtained from this study reveal that after consuming the modified diet containing watermelon seed, serum triglyceride (TG) and VLDL-C of the treated group were significantly decreased (p < 0.05 and p < 0.05 respectively) in comparison to that of the control group.Serum total cholesterol, LDL and AI (Atherogenic Index) were decreased whereas HDL (good cholesterol) increased in the treated group compared to that of the control group (Table -4).Arginine (900 mg/ g of N) present in watermelon seeds reported to have positive effect on serum lipid profile parameters.Endothelial nitric oxide synthase (eNOS) helps in the production of Nitric Oxide (NO) from l-arginine.NO plays an important role in regulation of endotheliumdependent vasodilatation 14 .59.64% of Linoleic acid is present in watermelon seed kernels 1 which can be metabolized into to gamma-linolenic acid (GLA) in the body.According to some preliminary evidence GLA, either alone or in combination with omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may help to reduce high blood pressure 15 .In mammalian metabolism Arachidonic acid (AA) is formed from Linoleic acid (LA) by subsequent ∆ 6 desaturation, chain elongation and Helvetic∆ 5 desaturation.In this metabolic pathway ∆ 6 desaturation step is ratelimiting and the step can be by-passed by dietary g -linolenic acid (GLA).Most of the GLA is elongated to dihomog-linolenic acid (DGLA) by the action of elongase and a small amount of GLA is desaturated by ∆ 5 desaturase into AA.The DGLA can enter into cycloxygenase pathway to form prostaglandins of the 1-series (PGE1) additionally or alternately it can enter into 15-lipoxygenase pathway to produce eicosatrienoic acid (15-HETrE).The PGE1 and 15HETrE have been proved to have suppressive effects on chronic inflammation, hypotensive effect through vasodilation and anti-atherosclerotic effect by retarding the vascular smooth muscle cell proliferation 16 .So, the presence of high amount of linoleic acid in watermelon seed kernels may be one of the possible reasons of improving lipid profile parameters.

Conclusion
Worldwide studies have been done to make use of herbal medicine.The proposed research work showed that consumption of watermelon seed kernel would improve lipid profile parameters, therefore may be useful in prevention and treatment of cardiovascular diseases.Presence of BCAAs and Vitamin-E in watermelon seed kernels are probably responsible for its hypoglycemic property.Thus, watermelon seed kernel may be used for the treatment of various ailments without any undesirable side effect, especially in those countries in which more classical therapeutic approach is not easily available.Still there is an ample scope of research to expose hitherto unknown bioactive ingredients and their mechanism of action responsible for the positive health benefits of these seeds.