Isolation and Characterization of Blueberry Polyphenolic Components and Their Effects on Gut Barrier Dysfunction

Highbush blueberries contain anthocyanins and proanthocyanidins that have antimicrobial and anti-inflammatory bioactivities. We isolated and characterized three polyphenolic fractions, a total polyphenol fraction (TPF), an anthocyanin-enriched fraction (AEF), and a proanthocyanidin-enriched fraction (PEF), from freeze-dried blueberry powder and evaluated their effects on an in vitro model of gut barrier dysfunction. High-performance liquid chromatography chromatograms illustrate successful fractionation of the blueberry powder into TPF, AEF, and PEF. AEF contained 21 anthocyanins, and PEF contained proanthocyanidin oligomers of (epi)catechin with primarily B-type interflavan bonds. The model uses a strain of Escherichia coli to disrupt a Caco-2 cell monolayer on Transwell inserts. Barrier function was measured by transepithelial electrical resistance (TEER), a marker of membrane permeability. All fractions were able to restore TEER values after an E. coli challenge when compared to the control, while AEF was able to attenuate the E. coli-induced decrease in TEER in a dose-dependent manner.