Bigeye tuna (Thunnus obesus) contains high nutritional value but the flesh is extremely susceptible toward lipid oxidation caused by ROS. Tuna fish encompass numerous antioxidant compounds to defend the PUFAs and nutrients against the lipid deterioration that may lead to discoloration, undesirable flavor, the formation of toxic compounds, nutrient change, poor texture, and bad odor. Among them, sulfur- and selenium-containing compounds have been studied for their antioxidant properties and radical scavenging activity. However, fish are not able to synthesize these compounds and they must obtain them from feeding, which shapes gut microbiota. Numerous fungi and bacteria are known to biosynthesize antioxidants, thus, fish gut microbiota would be a potential source of sulfur- and selenium- containing antioxidants. The aim of this study was to detect the presence of sulfur- and selenium- containing antioxidant compounds in cultures coming from Bigeye tuna intestine. For that, the contents and mucosa from the proximal and distal section of Bigeye tuna intestine were collected, cultured in different growth media and incubated for different times. After, these compounds were measured in culture supernatants and pellets by means of HPLC-ICP-MS. Ten sulfur- and five selenium-containing compounds were found, demonstrating tuna gut microbiota as a source of antioxidants.
