Antioxidant activity of Cod (Gadus morhua) protein hydrolysates: in vitro assays and evaluation in 5% fish oil-in-water emulsion.

Cod protein hydrolysates were fractionated according to the molecular mass into three fractions of >5 kDa, 3-5 kDa and <3 kDa using an ultrafiltration membrane system. The antioxidative activity of the crude hydrolysates and the fractions were investigated, both in in vitro assays (DPPH radical scavenging activity, reducing power, Fe²âº chelating activity and inhibition of lipid oxidation in liposome model system), and in 5% fish oil-in-water emulsions. The <3 kDa fractions had very good radical scavenging activity, Fe²âº chelating activity and reducing power while the fraction 3-5 kDa resulted in higher protection against oxidation in the liposome model system. When tested in 5% oil-in-water emulsions, all the fractions, including the crude protein hydrolysate, were able to protect fish oil against oxidation in an iron induced oxidation system. However, none of the peptide fractions were effective in preventing tocopherol loss and showed no tocopherol sparing property. Volatile oxidation products showed an interaction between the aldehydes and the protein/peptides added in the emulsions, and this needs further investigation.

Cardioprotective effect of squalene on lipid profile in isoprenaline-induced myocardial infarction in rats.

We studied the cardioprotective effect of squalene on isoprenaline-induced myocardial infarction in male albino rats with respect to changes in the levels of lipid components in plasma and heart tissue. Prior administration of 2% squalene in feed for 45 days significantly reduced the isoprenaline-induced elevation in the levels of cholesterol, triglycerides, and free fatty acids in plasma and heart tissue of rats following myocardial infarction. It exerted an antilipidemic effect by reducing the level of low-density lipoprotein cholesterol with a parallel rise in the level of high-density lipoprotein cholesterol in plasma of experimental rats. A tendency to prevent the isoprenaline-induced depletion of phospholipids in the myocardium of experimental rats was also observed. In the present study, the pretreatment with squalene significantly counteracted the isoprenaline-induced lipid peroxidation and maintained the rats at near normal status. The results of the present study indicate that the overall cardioprotective effect of squalene is probably related to an inhibition of lipid accumulation by its hypolipidemic properties and/or its antioxidant properties.

Protective effect of taurine on myocardial antioxidant status in isoprenaline-induced myocardial infarction in rats.

We have examined the protective effect of taurine on the myocardial antioxidant defense system in isoprenaline (isoproterenol)-induced myocardial infarction in rats, an animal model of myocardial infarction in man. Levels of diagnostic marker enzymes in plasma, lipid peroxides and reduced glutathione, and the activity of glutathione-dependent antioxidant enzymes and anti-peroxidative enzymes in the heart tissue were determined. Intraperitoneal administration of taurine significantly prevented the isoprenaline-induced increases in the levels of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and creatine phosphokinase in the plasma of rats. Taurine exerted an antioxidant effect against isoprenaline-induced myocardial infarction by preventing the accumulation of lipid peroxides and by maintaining the level of reduced glutathione and the activity of glutathione peroxidase, glutathione-S-transferase, catalase and superoxide dismutase at near normality. The results indicated that the cardioprotective potential of taurine was probably due to the increase of the activity of the free radical enzymes, or to a counteraction of free radicals by its antioxidant nature, or to a strengthening of myocardial membrane by its membrane stabilizing property.