Screening for metabolic syndrome application of a herring by-product hydrolysate after its separation by electrodialysis with ultrafiltration membrane and identification of novel anti-inflammatory peptides

The seafood industry is an important producer of by-products which can represent 50% of fish and contain valuable molecules for the human health. The search of bioactive peptides has increased since the last decades and marine organisms revealed a high richness. A herring milt hydrolysate has been separated by electrodialysis with ultrafiltration membrane (EDUF). Four fractions were collected: two anionic and two cationic, with respectively higher presence of acidic amino acids for the first ones and basic amino acids for the seconds. The higher migration rate was reported for the cationic, revealing the higher presence of cationic peptides and free basic amino acids in the initial milt herring hydrolysate. Both cationic fractions have decreased the inducible nitric oxide synthase (iNOS) activation in the macrophage cells at 1 ng/ml (−11.65% and −13.22%) and 100 pg/ml (−17.58% and 15.51%), demonstrating their in vitro anti-inflammatory effect. The oxygen radical absorbance capacity (ORAC) test revealed an antioxidant activity of 460.67 µmolTE/g for the initial hydrolysate, 386.20 µmolTE/g after EDUF separation and 343.49 µmolTE/g for the anionic fraction A50. No effects on the glucose uptake activity was reported for any fraction. In addition, two new cationic peptide sequences (IVPAS and FDKPVSPLL) from herring milt hydrolysate were identified and demonstrated an in vitro anti-inflammatory activity. This study highlighted the potential use of milt herring hydrolysate for prevention of the metabolic syndrome.