The inhibitory effects of pure flavonoids on in vitro protein glycosylation.

Non-enzymatic glycosylation of proteins is the major cause of diabetic complications, such as cardiovascular disorders, retinopathy, nephropathy and neuropathy. It seems that protein glycosylation can be inhibited effectively by antioxidants. Several flavonoids, such as rutin, kaempferol, quercetin, apigenin, naringin, morin and biochanin A were selected to determine their antioxidant effects on in vitro insulin, hemoglobin and albumin glycosylation. The optimal glucose concentration and incubation time were obtained for each protein. Then, the inhibition percentage of protein glycosylation was measured in the presence of three different concentrations (0.5, 5, 10 microg/ml) of each flavonoids by a colorimetric method. The results demonstrated that biochanin A, the best inhibitor of insulin and hemoglobin glycosylation, inhibits their glycosylation 100% and 60%, respectively. Glycosylation of albumin was inhibited 100% by both biochanin A and apigenin. Therefore, it seems probable that plants containing flavonoids may have preventive effects in diabetic complications.