Mate extract is superior to green tea extract in the protection against chicken meat protein thiol oxidation

Water soluble caffeic acid derivatives in aqueous extracts of mate (Ilex paraguariensis) showed a direct dose-dependent response, protecting protein thiols in a chicken breast meat model system when oxidation was initiated by a lipophilic radical initiator (2,2'-azobis(2,4-dimethylvaleronitrile; AMVN). In contrast, an inverse dose-dependent response was obtained when initiated by a hydrophilic radical initiator (2,2'-azobis(2-amidinopropane)dihydrochloride; AAPH), pointing toward a mechanism, where a specific concentration of water-soluble polyphenol yields optimum protection. Optimal concentrations of mate extract for the protection of thiols against radicals initiated in the lipid phase (AMVN) or in the aqueous phase (AAPH) were 0.1-0.5% and 0.01-0.1%, respectively. Green tea (Camellia sinensis) extract showed a pro-oxidative effect involving quinones from oxidation of pyrogallol-type catechins (epigallocatechin-3-gallate (EGCG), gallocatechin-3-gallate (GCG), and epicatechin-3-gallate (ECG)) and not the catechol-type catechins (catechin and epicatechin).