Interaction of free arginine and guanidine with glucose under thermal processing conditions and formation of Amadori-derived imidazolones

•Guanidine and arginine formed both covalent and non-covalent interaction products.•Guanidine formed Amadori compounds and imidazolone derivatives.•The imidazolinone derivatives of guanidine exhibited non-covalent interactions.•Arginine formed imidazolinone and Amadori-derived imidazolinone derivative.•Arginine also formed methylglyoxal-derived hydroimidazolones.

To investigate the reactivity of free guanidine and arginine in the formation of imidazolinone derivatives, model systems of guanidine or arginine/glucose or 13[C-6]-glucose were heated in aqueous solutions at110 °C for 3 h and the residues were analyzed by ESI/qTOF/MS using MS/MS and isotope labeling techniques. The analysis of the data indicated that guanidine and arginine formed both covalent and non-covalent interaction products. Covalent interactions included Amadori rearrangement at the α-nitrogen with glucose and imidazolinone formation with 3-deoxy-glucosone at the guanidine side-chain. Non-covalent interactions, such as self-interaction and interaction with free guanidine or arginine and glucose, were also observed. Guanidine underwent three sequential Amadori rearrangements and the free and mono-glycated guanidine also formed imidazolinone derivatives and their corresponding dehydration products and at the same time exhibiting various non-covalent interactions. On the other hand, arginine formed free Amadori product, free imidazolinone and Amadori-derived imidazolinone derivative in addition to methylglyoxal-derived hydroimidazolones.