Separation of proanthocyanidin polymers from American cranberries and predictive modeling of depolymerization using response surface methodology

Abstract

About 85% of proanthocyanidins in the American cranberries are polymers with degree of polymerization above 4. These polymers have lower absorption rates and bioactivities than oligomers of smaller sizes. In the present study, proanthocyanidin polymers were separated from cranberries using a two-step chromatographic method and depolymerized into a mixture of monomers, dimers, trimers, and tetramers. Adding epicatechin as a chain breaker yielded 1659 mg oligomers per gram of polymers compared to a yield of 221 mg oligomers in the absence of epicatechin under predicted optimal conditions. Predictive modeling using response surface methodology showed that higher yields of oligomers were achieved at higher temperature and moderate acid concentration in the presence of epicatechin. Shorter reaction time and high acid concentration were favored in the absence of epicatechin. This research provided a practical approach to depolymerize proanthocyanidin polymers and had the potential to increase bioavailability and bioactivity of proanthocyanidins in cranberry extracts. Practical applications Cranberry extracts containing bioactive proanthocyanidins are being used as dietary supplements for prevention of urinary tract infections and other chronic conditions. However, about 85% of cranberry proanthocyanidins are polymers with degree of polymerization above 4. These polymers are not absorbable, therefore, their bioactivities were much lower than oligomers of smaller sizes. This research provided a practical approach to separate proanthocyanidin polymers from cranberries and convert them to monomers, dimers, trimers, and tetramers with higher absorption rates than polymers.