Synergistic inhibition against heterocyclic amines by amino acid combinations: Focus on carbonyl-amine reactions of methylglyoxal and glyoxal

In this study, critical reactants were identified in glycine/glucose/creatinine model system to clarify the formation pathways of imidazoquinoxaline-type heterocyclic amines (IQx-type HAs). It has been confirmed that the condensation between pyrazines and creatinine was the critical step to produce IQx-type HAs. There was a conversion between methylglyoxal and glyoxal, and their carbonyl-amine reaction was a route for the production of 2,5-dimethylpyrazine and methylpyrazine. When cysteine was combined with proline at the mass ratio of 4:1 (2 mg/mL in total), the inhibitory rate of MeIQx and IQx in glucose/creatinine/glycine model system increased to 62 % and 55 %, respectively. The synergistic inhibition of cysteine-proline combinations was further assessed in roast yellow croaker, and the total content of IQx-type HAs decreased from 4.99 +/- 0.48 ng/g of the control group to 2.46 +/- 0.21 ng/g. The carbonyl scavenging rate of corresponding cysteine-proline combinations also increased compared with that of single agents. These findings suggest that scavenging methylglyoxal and glyoxal simultaneously to control the production of pyrazines may be a potential inhibitory strategy to enhance the suppression of IQx-type HAs formation.