Investigating the\nPresence of Selenoneine, Ergothioneine,\nand Selenium-Containing Biomolecules in Fish and Fish-Derived Commercial\nProducts

Two potent antioxidants, selenoneine\nand ergothioneine, have been\ndetermined simultaneously for the first time in the muscle of highly\nconsumed fish and in fish-derived products. The extraction methods\nwere optimized, and their subsequent analysis was performed by HPLC-ESI-MS/MS.\nBest extraction efficiency (106 ± 3 and 104 ± 5%) was attained\nby performing a simple aqueous extraction containing 100 mmol L<sup>–1</sup> ammonium acetate or ammonium formate as extractants.\nSelenoneine and ergothioneine were simultaneously detected in tuna\n(0.306 ± 0.006 and 3.5 ± 0.2 μg g<sup>–1</sup>) and swordfish (0.14 ± 0.02 and 1.1 ± 0.4 μg g<sup>–1</sup>) muscle tissues, while in fish roe and in farmed\nsalmon, only ergothioneine was detected (with contents ranging 0.03–3.3\nμg g<sup>–1</sup>). Moreover, the presence of their respective\nmethylated forms was also considered. Additionally, Se-containing\nbiomolecule profiles from water-soluble proteins were obtained by\nSEC-ICP-MS analysis. Results revealed similar profiles between fish\nand fish roe, whereas for ultraprocessed fish products, Se seems to\nbe mostly associated with low-molecular-weight biomolecules. The results\nincluded in this work may contribute to a better understanding of\nthe relations between selenoneine and ergothioneine in fishery products\nas well as their fate and potential modifications of Se-containing\nbiomolecule profiles during fish processing.