Consumption of phenolic-rich foods and beverages is reported to maintain the structures and physiological functions of serum proteins under chronic hyperglycemia. However, mechanisms of stabilization by polyphenols have not been elucidated.  In this study, human serum albumin (HSA) was used as a model to evaluate the potential anti-glycation activities of phenolic compounds. After 3 weeks of incubation with glucose, the intrinsic fluorescence of HSA increased significantly, indicating extensive glycation of the protein. Native PAGE and CD results showed that glycated HSA had a higher affinity for Cu2+ and a lower affinity for Fe3+ compared to native HSA. Moreover, spectrophotometric experiments showed that heme binding ability of HSA was impaired as glycation developed. Co-incubation with phenolic compounds such as the tea polyphenol epigallocatechin gallate effectively protected HSA structure and maintained normal metal and heme binding functions under high glucose concentrations. We propose that polyphenols could indirectly reduce oxidative stress in vivo by ensuring that serum proteins buffer the levels of redox active metals even when glucose levels are elevated. This indirect mechanism may contribute to the beneficial effects of phenolic-rich diets for hyperglycemic individuals.

Polyphenols maintain the metal and heme binding abilities of human serum albumin exposed to hyperglycemic conditions

246th National Meeting (2013)

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