Functional and Antioxidant Properties of Protein Hydrolysates from Grey Triggerfish Muscle and in vivo Evaluation of Hypoglycemic and Hypolipidemic Activities

Abstract

Functional properties and antioxidant activities in vitro and hypoglycaemic and hypolipidemic activities in vivo of protein hydrolysates prepared from muscle of grey triggerfish (Balistes capriscus) were investigated. Baliste protein hydrolysates (BPHs) were obtained by treatment with crude enzyme preparations from Bacillus mojavensis A21 (BPH-A21), crude enzyme extract from sardinelle (Sardinella aurita) viscera (BPH-S) and crude enzyme extract from Zebra blenny (Slaria basilisca) viscera (BPH-Z). The protein hydrolysate BPH-A21, BPH-S and BPH-Z contained high protein content 87.61%, 74.53% and 54.18%, respectively. The protein hydrolysates had an excellent solubility and possessed interfacial properties, which were governed by their concentrations. Analysis of amino acid composition revealed that Baliste capriscus protein hydrolysates (BPHs) were valuable sources of essential amino acids and rich in lysine and Arginine, which is one of the active ingredients for blood glucose control by inducing insulin release in both rats and humans. Treatment of alloxan-induced diabetic rats (AIDR) with BPHs revealed a significant inhibition of α -amylase activity in serum, as well as a reduction of blood glucose and glycated hemoglobin (HbA1c) levels in diabetic rats. Further, BPHs also decreased significantly the triglyceride (TG), totalcholesterol (TC) and LDL-cholesterol (LDL-c) levels in the serum and liver of diabetic rats, while they increased the HDL-cholesterol (HDL-c) level, which helped to maintain the homeostasis of blood lipids. Furthermore, BPHs exhibited potent protective effects against heart attack markers by reversing myocardial enzyme serum back to normal levels. BCPHs may also a marked decrease in the level of serum bilirubin as well as in the activities of alanine aminotransferase (ALT), alkaline phosphatase (ALP), and gamma-glutamyl transpeptidase (GGT). These beneficial effects of BPHs were confirmed by histological findings in the hepatic and pancreatic tissues of diabetic rats. Indeed, they avoid lipid accumulation in the hepatocytes and protect the pancreatic β-cells from degeneration. Overall, the findings of the current study indicate that BPHs significantly attenuated hyperglycemia and hyperlipidemia in AIDR. The antioxidant activities of protein hydrolysates at different concentrations were evaluated using various in vitro antioxidant assays, including 1,1-diphenyl-2-picrylhydrazyl (DPPH.) radical method, reducing power assay, chelating activity, β-carotene bleaching and DNA nicking assay. All protein hydrolysates showed varying degrees of antioxidant activity. BPH-Z had the highest DPPH radical scavengingactivity (95% at 40 mg/ml) and higher ability to prevent bleaching of β-carotene than BPH-S and BPH-A21 (p<0.05). However, BPH-S exhibited the highest metal chelating activity (76,24% at 0,4 mg/ml) and the strongest protection against hydroxyl radical induced DNA breakage (p<0.05).