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Effects of Catechins on Nᵋ-(Carboxymethyl)lysine and Nᵋ-(Carboxyethyl)lysine Formation in Green Tea and Model Systems

Jiao, Ye, Quan, Wei, He, Zhiyong, Gao, Daming, Qin, Fang, Zeng, Maomao, Chen, Jie
Journal of agricultural and food chemistry 2019 v.67 no.4 pp. 1254-1260
catechin, drying, enzyme inactivation, green tea, lysine, models, transition elements
The effects of catechins on Nᵋ-(carboxymethyl)lysine (CML) and Nᵋ-(carboxyethyl)lysine (CEL) formation in green tea and related model systems were investigated in this study. Since the first step of green tea processing entails enzyme inactivation, the catechin content was maintained at a high level during processing. However, drying still had a great effect on CML and CEL formation, while other steps also contributed. Hence, model systems were developed to analyze the effects of catechins on CML and CEL formation. Catechins ((−)-epicatechin gallate, (−)-epigallocatechin, and (−)-epigallocatechin gallate) could inhibit CML formation in the model imitating the condition of green tea processing, though the inhibitory efficiency was reduced by transition metals. This suggested that catechins could inhibit CML formation in the real tea system, though the inhibitory efficiency may be reduced by tea components which promote its synthesis. However, CEL formation was not always inhibited by the tested catechins, though catechins could significantly decrease the content of methylglyoxal which is considered an important intermediate. Consequently, the main pathway of CEL formation may not be through methylglyoxal.