Fresh coconut kernel contains 5% protein. The coconut kernel protein (CKP) has been reported to be of good nutritional quality. Our studies on solubility and precipitation showed that 70-80% of the coconut kernel proteins are globulins. The globulin of the coconut kernel is a good protein from the point of digestibility and biological value. Individual amino acid analysis of coconut kernel protein using HPLC revealed that coconut kernel protein has a much higher amount of glutamic acid (27.7%) and L-arginine (17.8%). Studies showed that the biologically important functions of coconut kernel proteins are due to the presence of L-arginine.
Studies showed that rats fed coconut kernel protein; increased hepatic degradation of cholesterol to bile acids, increased hepatic cholesterol biosynthesis, and decreased esterification of free cholesterol. But, in the intestine, cholesterogenesis was decreased. The kernel protein also caused decreased lipogenesis in the liver and intestine. In addition, the synthesis and secretion of VLDL decreased in hepatocytes isolated from rats fed coconut kernel protein. These beneficial effects of the kernel protein are attributed to its very low lysine/arginine ratio. Coconut kernel protein caused reduction in lipid peroxidation in rats fed PUFA rich sunflower oil as the dietary fat.
It was found that coconut kernel has cardioprotective effect against isoproterenol induced myocardial infarction in rats, which may be attributed to the high content of L-arginine present in it. Recently, it was found that dietary supplementation of CKP might have greater significance in reducing the extent of oxidative stress and inflammatory responses associated with myocardial infarction by modulating nitric oxide pathway, and by its ability to inhibit NF-κB and TNF-α activation. Influence of coconut kernel protein on lipid metabolism in alcohol fed rats were also studied. It was found that coconut protein increased the concentration of hepatic bile acids and fecal excretion of neutral sterols and bile acids.
Our studies indicated that CKP has potential antidiabetic activity which may be mediated through arginine-NO pathway. In another study, we showed that CKP has potential effect in lowering oxidative stress associated with diabetes. This beneficial effect of CKP is due to the higher amount of L-arginine present in it. CKP feeding attenuated the increase in glucose and decrease in insulin levels in diabetic rats. Glycogen levels in the liver and the activities of carbohydrate metabolizing enzymes in the serum of diabetic rats treated with CKP were reverted back to the normal levels. CKP also alleviated the inflammatory responses associated with diabetic condition by beneficially modulating the Nfkb pathway. Studies demonstrated that coconut protein is able to reduce hyperlipidemia and peroxidative damage induced by high cholesterol containing diet.