Natural peptides with antioxidant activity from Atlantic cod and Atlantic salmon residual material

Summary. Water-soluble peptides/proteins with molecular weight below 10 kDa were isolated from residual material of cod (liver, skin, and cod mix i.e. skin, frames, and viscera), and salmon (skin, and salmon mix i.e. skin, frames, and viscera) by cut-off filtration. Peptide motifs with reported bioactivity were identified in all samples by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) (Orbitrap), bioinformatics, and database search. Peptides with potential type 2 diabetes, cardio system, immunomodulation, prolyl endopeptidase (PEP), and antioxidant activity were detected. The potential antioxidant activity in the samples was confirmed by two antioxidant assays, namely hydroxyl radical scavenging activity (HRSA), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical cation decolorization assay. In these assays the salmon samples were found to possess higher antioxidant activity than the cod samples. All samples except the cod skin were found to have higher antioxidant activity than alanine-histidine (AH), a dipeptide with known antioxidant activity. Industrial relevance. Residual material from fisheries and aquaculture makes up large quantities of material. Although previously regarded as waste this material has valuable components that are of interest for the biotech industry. The fractionation process utilized in this work offers the possibility for simple isolation of interesting peptides with antioxidant activity. This method should be of interest for the food industry and biotech industry for product development