In vitro and in vivo anti-diabetic and anti-hyperlipidemic effects of protein hydrolysates from Octopus vulgaris in alloxanic rats.

This study aims to examine the effects of non-hydrolyzed octopus (Octopus vulgaris) muscle proteins (NHOPs) and their hydrolysates (OPHs) on alloxan induced diabetes in Wistar rats (AIDR). Animals were allocated into seven groups of six rats each: control group (C), diabetic group (D) and diabetic rats treated with acarbose (D + Acar), non-hydrolyzed octopus proteins (D + NHOPs) and octopus proteins hydrolysates (D + OPHs) groups. The diabetic rats presented a significant increase in glycemic status such as α-amylase activity (in plasma, pancreas and intestine), hepatic glycogen, blood glucose and glycated hemoglobin (HbA1c) levels, as well as a significant decrease in the levels of plasma insulin and total hemoglobin compared to control group. In addition, plasma and liver contents in total cholesterol, triglycerides and LDL-cholesterol significantly increased in AIDR compared to control group. However, the daily administration of OPHs for 30 days improved the glucose tolerance test, the glycemic status of diabetic rats and corrected the lipid profiles. Further, a significant increase in the activities of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and gamma-glutamyl transpeptidase as well as in the level of plasma bilirubin on diabetic status was observed, indicating considerable hepatocellular injury. OPHs treatment was found to attenuate the increased activities of the plasma enzymes produced by diabetes and caused a subsequent recovery towards normalization compared to the control group. By contrast, the NHOPs treatment was found to increase the glucose metabolic disorders in AIDR. These beneficial effects of OPHs were confirmed by histological findings in the hepatic and pancreatic tissues of diabetic treated rats. Indeed, they avoid lipid accumulation in the hepatocytes and protect the pancreatic ß-cells from degeneration. Our results thus suggest that OPHs may be helpful in the preventing from diabetic complications by reversing hepatotoxicity.

Octopus vulgaris protein hydrolysates: characterization, antioxidant and functional properties.

Composition, functional properties and in vitro antioxidant activities of octopus (Octopus vulgaris) protein hydrolysates (OPHs) were evaluated. OPHs were prepared by treatment with commercial Esperase (OPH-Esp), alkaline protease extract from Zebra blenny (Salaria basilica) (OPH-ZB) and enzyme preparation from Bacillus subtilis A26 (OPH-A26). OPHs showed different degrees of hydrolysis (DH from 17.6 to 21%), and hydrophobic/hydrophilic peptide ratio. The amino acid profiles of OPHs showed a high level of essential amino acids, and Lys was the most abundant amino acid. Enzymatic hydrolysis improved solubility significantly as well as emulsifying and foaming properties of octopus proteins. The emulsifying activity index of OPHs decreased with increasing concentrations. Conversely, the foaming abilities increased as the hydrolysate concentrations increased. For the antioxidant activities, five different in vitro assay systems were investigated. All hydrolysates displayed various degrees and dose dependant antioxidant activities. The highest DPPH scavenging activity and reducing power were achieved by OPH-A26. OPH-Esp displayed the highest ability to prevent the bleaching of ß-carotene, whereas OPH-ZB exhibited the highest protection against hydroxyl radical induced DNA breakage. The results suggested that OPHs could be used, as a promising source of functional peptides with antioxidant activities, to formulate functional foods.

In-vitro antioxidant and functional properties of protein hydrolysates from golden grey mullet prepared by commercial, microbial and visceral proteases.

Bioactive Liza aurata protein hydrolysates (LAPHs) were prepared by treatment with Trypsine (PH-TR), Esperase (PH-ES), enzyme preparations from Pseudomonas aeruginosa A2 (PH-A2), Bacillus subtilis A26 (PH-A26) and Liza aurata (PH-LA). Their functional properties and antioxidant activities were evaluated. The hydrolysates had degree of hydrolysis (DH) values ranging from 8.15 % to 13.05 %. Reverse-phase HPLC analyses of the LAPHs showed considerable variation in peptide composition. All hydrolysates had high protein content (83.14 %-86.43 %). Glutamic acid, Glutamine (Glx) and Lysine (Lys) were the most abundant amino acids. All protein hydrolysates had a good solubility emulsifying and foam properties were found to be considerably improved by enzymatic hydrolysis. In addition, all hydrolysates showed varying degrees of antioxidant activities evaluated by various in vitro tests. Further, all LAPHs did not show hemolytic activity towards human erythrocytes. The results thus revealed that protein hydrolysates from golden grey mullet could be used as food additives possessing both antioxidant activity and functional properties.

The influence of the extent of enzymatic hydrolysis on antioxidative properties and ACE-inhibitory activities of protein hydrolysates from goby (Zosterisessor ophiocephalus) muscle.

Antioxidant properties and angiotensin-converting enzyme (ACE) inhibitory activities of protein hydrolysates from goby (Zosterisessor ophiocephalus) muscle, with different degrees of hydrolysis (DH) from 5 to 25%, prepared by treatment with crude proteases extract from smooth hound intestines, were investigated. Goby protein hydrolysates (GPHs) are rich in Gly and Thr, which accounted for 14.1-15% and 11.6-13.2% of the total amino acids, respectively. The antioxidant activities of GPHs were investigated by using several in vitro assay systems. All GPHs exhibited significant metal chelating activity and DPPH free radical-scavenging activity, and inhibited linoleic acid peroxidation. For the ACE-inhibitory activity, as the DH increased, the activity of GPHs increased. The obtained results revealed that antioxidant and ACE-inhibitory activities of GPHs were influenced by the degree of hydrolysis. A medium degree of enzymatic hydrolysis was appropriate to obtain GPHs with good antioxidant activity, while small peptides were essential to obtain high ACE inhibitory activity.