Binding of epigallocatechin-3-gallate to myoglobin attenuated hemin release and lipid peroxidation: New insight into the antioxidant mechanism.

Myoglobin (Mb) is an effective inducer for lipid peroxidation in muscle-based food and the protein-flavonoid bindings have been widely reported. The effect of the interaction between epigallocatechin-3-gallate (EGCG, a dominant flavonoid in green tea) and Mb on lipid peroxidation was rarely explored. This work systematically investigated the interaction between EGCG and Mb through the experimental and theoretical methods, to elucidate the structural mechanism whereby EGCG regulated the redox behavior and stability of Mb. EGCG bound into the central cavity to form Mb-EGCG complex via static quenching mechanism, and hydrophobic forces played a predominant role during their interactions. Free hemin (rather than inorganic iron) liberated from hemoprotein made a major contribution to Mb-mediated lipid peroxidation, and EGCG obviously attenuated Mb-induced lipid peroxidation in liposome or muscle. The suppressive mechanism of EGCG was likely ascribed to that the binding of EGCG could promote the compactness of hemoprotein and narrow the crevices around heme groups, which led to the reduction of ferric (met-) Mb and inhibition of free hemin release. In accordance with its effects on Mb redox state and stability, EGCG ‌efficiently preserved the red color of hemoproteins and meat during their storages. Therefore, our results about the interactions of EGCG with redox-active Mb provide a new insight into the antioxidant mechanism of EGCG, and are favorable to the potential applications of natural flavonoids in the good quality and freshness of relative hemoproteins-containing food.