Inhibition of non-enzymatic protein glycation by pomegranate (Punica granatum)

Abstract

The non-enzymatic glycation of proteins is an oxidative-dependent process inhibited by phenolic compounds. This study investigates the effect of extracts of pomegranate fruit and its various parts (aril, peel, and membrane) on the in vitro glycation of albumin. Extracts were analyzed for phenolics content, FRAP antioxidant capacity and their effect on fructose mediated glycation of bovine serum albumin. Compared to a control fruit, apple, whole pomegranate fruit exhibited a much higher total phenolic content and antioxidant potential. Pomegranate decreased glycation by 80% at a phenolics concentration of 2.5 μg gallic acid equivalents (GAE)/ml; apple, at this concentration, inhibited protein glycation by only 20%. Pomegranate membrane exhibited the highest total phenolics content and antioxidant potential compared to the aril and peel. At 2.5 μg GAE/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 incubated at the same antioxidant capacities. These results demonstrate that the inhibitory activity of pomegranates was concentrated in the membrane and is attributed to ellagitannins, potent inhibitors of the glycation process.