Proteomic approaches to identify antioxidant peptides from the microalga Tetraselmis chuii after its simulated orogastric digestion

Over the last few years, the interest in bioactive peptides derived from microalgae has grown significantly due to their potential health benefits. Within the different microalgae species, the green microalga Tetraselmis chuii stands out for its protein profile composition and essential amino acids¹. The proteomic analyses of simulated gastric or gastrointestinal digestion phases, both in vitro and in silico, have become one of the most widely investigated strategies to evaluate bioactive peptides from microalgae proteins.

T. chuii biomass was pretreated with a combination of freeze–thaw cycles and ultrasounds. Proteomic analysis was carried out by HPLC coupled with tandem mass spectrometry. The functional analysis of the proteome was carried out with OmicsBox software. The annotated proteins were classified into three functional groups—cellular component, molecular function, and biological processes—using BLAST 2GO Methodology. n silico gastric digestion was performed by the Rapid Peptides Generator (RPG); pepsin was selected as the digestive enzyme. In parallel to this, in vitro orogastric digestion was carried out following the INFOGEST protocol². The antioxidant capacity of the digests was evaluated by ORAC and ABTS assays.

The proteomic and functional analysis allowed for the identification of 287 annotated proteins, which were classified into three different groups: 254 sequences (33.5% of total) were associated with a biological process; 222 sequences (35.5%) were classified as proteins involved in molecular function; and 240 sequences (31.0%) were identified as proteins constituent of a cellular component. In silico gastric digestion of the identified proteins revealed the release of 14,774 peptides, most of them (79%) containing between two and ten amino acids. Among the low-molecular-weight peptides produced during the in silico analysis, 24% contained aromatic amino acids, which could be responsible for the radical scavenging capacity determined in the in vitro orogastric digests of T. chuii.