INFORM June 2026

ANTIOXIDANTS INFORM 25

increases their ability to stabilize radicals and slow down oxidative processes. Not all amino acids contribute equally. Aromatic residues such as tryptophan and tyrosine are particularly effective due to their resonance-stabilized structures, which facilitate hydrogen donation and radical stabilization. Sulfur containing amino acids like cysteine and methionine also play a significant role, although cysteine can exhibit prooxidant behavior under certain conditions due to the formation of reactive sulfur radicals. Histidine, with its imidazole ring, contributes through proton transfer and radical trapping, while basic amino acids such as lysine

percent inhibition of lipid peroxidation, while its hydroxylated form, L-DOPA, shows much higher activity (about 68 percent), along with better reducing power and stronger radical scavenging and metal chelating effects. This clearly shows that even small changes in structure can significantly influence antioxidant behavior. FROM AMINO ACIDS TO ANTIOXIDANT PEPTIDES Bioactive peptides perform a wide variety of functions, mainly determined by their amino acid sequence and their source. This variation can also be observed in plant-derived peptides that have different functionalities.

and arginine participate through charge interactions and metal binding. The antioxidant performance of amino acids varies with the system in which they are applied. This system dependent behaviour highlights an important consideration for their practical application in food matrices. For example, tyrosine shows around 31 Structure of an amino acid, consisting of a central α -carbon bonded to an amino and carboxyl group with a variable side chain. Source: created at https://BioRender.com

Classification of amino acids based on side chain properties. Source: created at https://BioRender.com

Non-polar side chains

Charged side chains

Aspartic Acid

Glutamic Acid

Glycine

Alanine Valine

Leucine

Isoleucine

Acidic

Histidine

Lysine Basic

Arginine

Methionine Phenylalanine

Tryptophan

Proline

Polar uncharged side chains

Serine

Threonine

Cysteine

Tyrosine

Asparagine

Glutamine