The nonenzymatic glycation of proteins and the formation of advanced glycation endproducts in diabetes leads to the crosslinking of proteins and disease complications. Our study sought to demonstrate the effect of commonly consumed juices (pomegranate, cranberry, black cherry, pineapple, apple, and Concord grape) on the fructose-mediated glycation of albumin. Albumin glycation decreased by 98% in the presence of 10 μL of pomegranate juice/mL; other juices inhibited glycation by only 20%. Pomegranate juice produced the greatest inhibition on protein glycation when incubated at both the same phenolic concentration and the same antioxidant potential. Both punicalagin and ellagic acid significantly inhibited the glycation of albumin by ~90% at 5 μg/mL. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that pomegranate, but not apple juice, protected albumin from modification. These results demonstrate that pomegranate juice and two of its major constituents are potent inhibitors of fructose-mediated protein glycation.

The non-enzymatic glycation of proteins, an oxidative-dependent process, initiates the formation of advanced glycation endproducts (AGEs) which leads to protein crosslinking. This study investigates the effect of a phenolic whole pomegranate fruit extract and various parts (aril, peel, and membrane) of pomegranate fruit on the in vitro fructose-mediated glycation of albumin. Compared to apple, whole pomegranate fruit exhibited a much higher total phenolics content and antioxidant potential. Pomegranate fruit decreased glycation by 80% when incubated at a phenolic concentration of 2.5 μg gallic acid equivalents (GAE)/ml; apple, at this phenolic concentration, inhibited protein glycation by only 20%. Pomegranate membrane exhibited the highest total phenolics content and antioxidant potential compared to the pomegranate aril and peel. At 2.5 μg phenolics/ml, the membrane fraction decreased glycation by 85% compared to the aril (42%), and peel (75%). Pomegranate membrane also produced the greatest decrease in glycation when these fractions were incubated at the same antioxidant capacities. These results demonstrate that pomegranate fruit is a potent inhibitor of fructose-mediated albumin glycation when compared to whole apple. The inhibitory activity was concentrated in the pomegranate membrane and is attributed to the presence of punicalagin, which is not found in whole apple.