Isolation of specific cranberry flavonoids for biological activity assessment

Characterisation of cranberry compound biological activity is constrained by limitations in isolation methodology. A single rapid procedure for polyphenolic isolation was developed using semi-preparative-HPLC. Non-flavonoid compounds were removed by pre-purification procedures prior to semi-preparative-HPLC. Fractions were analysed to ascertain purity (99%) with HPLC and ESI mass spectrometric detection in negative ion mode and on-line diode array ultraviolet–visible spectroscopy. Isolated cranberry flavonols included quercetin-3-galactoside, quercetin-3-glucoside, quercetin-3-rhamnoside, myricetin-3-galactoside, myricetin-3-arabinofuranoside, and quercetin-3-O-(6″-p-benzoyl)-β-galactoside. Proanthocyanidin isolates contained monomers, dimers, trimers, and larger polymers. Anthocyanins consisted largely of galactoside and arabinoside conjugates of cyanidin and peonidin. Identities were confirmed using 1D-NMR- and 2D-NMR-spectrometry as well as reference standards. Flavonol fractions exhibited the highest antioxidant activity in a dosedependent manner, while the anthocyanin fraction exhibited the least activity. Biological activity studies of cranberry phenolics will benefit from the improved isolation procedures described in this study and the confirmation of antioxidant activities of various cranberry constituents.