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Introduction. Several studies have reported that marine peptides have antioxidant effect. However, few have focused on their cholesterol-lowering effect. Objective. The purpose of this study was to evaluate the effects of sardine (Sardina pilchardus ) and sardinelle (Sardinella aurita) protein hydrolysates on reverse cholesterol transport, and antioxidant status, in rat fed a cholesterol-enriched diet. Materials and methods. Eighteen male Wistar rats (350±15g) were divided into three groups, and fed 20% casein and 1% cholesterol for 15 days. During this period, two groups received by gavage sardine protein hydrolysates (HPS) or sardinelle (HPA) solution. The 3rd group received water (GC). Results. Cholesterolemia was 1.7-fold lower in hydrolysates fed groups. The lecithin: cholesterol acyltransferase (LCAT) activity was respectively, 1.7- and 1.6-fold higher in HPS and HPA groups. Phospholipids values of high density lipoprotein (PL-HDL ) were 1.4-fold lower in HPS compared with GC group. Cholesteryl esters amounts of HDL (CE-HDL ) were respectively, 1.7- and 1.5-fold higher in HPS and HPA groups. Liver and muscle thiobarbituric acid reactive substances (TBARS) were respectively reduced by 68% and 29% in HPS and 48.5% and 63.6% in HPA group. Superoxide dismutase (SOD) activity was increased by 32% in liver and 78% in muscle of HPA. Conclusion. It seems that HPS and HPA act favorably on reverse cholesterol transport, and improve oxidative stress, in rat fed cholesterol- enriched diet.

The angiotensin I-converting enzyme (ACE) inhibitory activities and antioxidant properties of thornback ray gelatin hydrolysates (TRGHs) prepared by treatment with proteolytic proteases from Bacillus subtilis A26, Raja clavata crude alkaline protease extract, Alcalase and Neutrase were investigated. All gelatin hydrolysates showed different degrees of hydrolysis and hydrophobic/hydrophilic peptides ratio. Moreover, they possess high protein content (70.04 ± 0.55–74.14 ± 0.28%). The antioxidant activity was assayed using various in vitro tests. The highest antioxidant activity was observed with hydrolysate obtained by treatment with A26 proteases (TRGH-A26) which exhibited a 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity with a concentration that produces 50% of inhibition (IC50) of 1.98 ± 0.02 mg/ml of sample, reduced the ferric ions with an absorbance at 700 nm of 0.962 ± 0.07, prevents bleaching of β-carotene with 73.02 ± 1.90% inhibition and gave an antioxidative efficacy of 180 ± 0.08 µmol/ml α-tocopherol equivalents at 5 mg/ml in the phosphomolybdenum assay. However, gelatin hydrolysate treated with Alcalase (TRGH-Alcalase) was the most potent to prevent DNA oxidation. For the ACE inhibitory activity, all hydrolysates displayed ACE-inhibitory activity. TRGH-A26 and TRGH-Alcalase exhibited the highest activity with 85 ± 0.65 and 82 ± 0.49%, respectively, at 5 mg/ml. The results revealed that TRGHs could be used as ingredients to formulate functional foods.

Protein hydrolysates are of a significant interest, due to their potential application as a source of bioactive peptides in nutraceutical and pharmaceutical domains. The present study was focused on the effect of protein hydrolysate from smooth hound (Mustelus mustelus) (SHPH) in the regulation of components of the food intake control such as satiety. SHPH was produced by intestinal digestive proteases from the same species. The amino acid analysis by GC/MS showed that the hydrolysate was rich in leucine, alanine, glycine, threonine, serine, lysine and glutamate. The molecular weights of peptides in SHPH were estimated by ESI-MS to be between 200 and 2500 Da. Biological in vivo capacities of SHPH in rats were evaluated by determination of the CCK-like peptides and insulin content using a clinical human radioimmunoassay. The food intake and the body weight of rats were measured during the period of treatment. Rats treated with SHPH showed a significant decrease in body weight at the end of treatment, as well as a decrease of food intake. Our findings revealed a possible mechanism of the beneficial effects of SHPH in appetite regulation, and this might be important to prevent the risk of a number of medical conditions including type II diabetes.