Synergistic and inhibitory effects of propolis and aspirin on structural changes of human hemoglobin resulting from glycation: an in vitro study

This study investigated the effects of the ethanolic extract of propolis (EEP) in the absence and presence of aspirin on the glycation-induced structural changes of human hemoglobin (Hb). Hb samples were incubated in the presence and absence of glucose (40 mM) for 5 weeks in the absence and presence of various concentrations of EEP and aspirin. Sampling was conducted at the end of each week, and the extent of glycation was evaluated by spectrophotometry, Thioflavin-T test, and by measuring free amino group contents and heme degradation products. Results showed that Hb was glycated by glucose after various incubation times reduced free amino group content, downturn absorption of and induced blue shifting in the UV–visible spectrum of Hb as well as increased amyloid structures and heme degradation. EEP prevented these changes and decreased the extent of glycation in a concentration-dependent manner. Aspirin also prevented glycation with the same efficacy as EEP (20 μg/ml). Surprisingly, the simultaneous presence of aspirin and EEP resulted in the extensive inhibition of glycation; in the 40 μg/ml concentration of EEP and aspirin, glycation was fully prevented in a synergic way. It is probable that EEP exerts its anti-glycation effect via its potent antioxidant and radical scavenging properties which decrease glycation-produced oxidative stress. In conclusion, EEP is to be introduced as an anti-glycation agent for the first time in this study. It could be developed as a natural agent for the design of new anti-glycation drugs aimed at reducing protein glycation as well as diabetic complications.