Cranberry Phytochemicals Inhibit Glycation of Human Hemoglobin and Serum Albumin by Scavenging Reactive Carbonyls

Abstract

The objective of this study was to investigate the inhibitory effects of cranberry phytochemicals on protein glycation. Cranberries were purified to yield a sugar‐free powder, which was fractionated into ethyl acetate fraction and water fraction. Water fraction was separated into water fraction‐I, II, and III. Antiglycation activities were tested using glycated hemoglobin (HbA1c), human serum albumin (HSA) ‐glucose, and HSA‐methylglyoxal assays. Cranberry powder and its fractions significantly inhibited the formation of HbA1c by 41.7–81.9 %. The concentrations of cranberry phytochemicals required to inhibit 50% of albumin glycation (EC50) in HSA‐glucose assay was lower than aminoguanidine except for water fraction‐I. The cranberry powder and fractions inhibited glycation of HSA by methylglyoxal. Cranberry phytochemicals scavenged 21.6–89.3% methylglyoxal within 6 hours. Fractions enriched with procyanidins showed higher antiglycation activities. Epicatechin, the constituent unit of procyanidins, were incubated with methylglyoxal and glyoxal at pH 7.4. Five adducts were detected and their structures were tentatively identified using HPLC‐ESI‐MSn. In conclusion, cranberry phytochemicals inhibited glycation of human hemoglobin and serum albumin by scavenging reactive carbonyls. This research is supported in part by Ocean Spray Cranberries, Inc.