“…Standards of amino acids, including L-asparagine, L-glutamic acid, L-alanine, L-leucine, L-serine, L-isoleucine, L-aspartic acid, L-valine, L-methionine, L-cysteine, L-phenylalanine, L-threonine, L-glutamine, L-proline, L-histidine, L-tryptophan, L-tyrosine, L-lysine, obtained from Sigma (Sigma-Aldrich, St. Louis, MO, USA), were of analytical grade (> 99 % purity) (Slobodianiuk et al 2019;Feshchenko et al 2021b;Slobodianiuk et al 2021f). All other reagents were of the highest purity.…”