Quantification of cranberry proanthocyanidins by normal-phase high-performance liquid chromatography using relative response factors.

INTRODUCTION: American cranberries (Vaccinium macrocarpon) contain primarily A-type proanthocyanidins (PACs), which have been shown to prevent urinary tract infection. Currently, the accurate quantification of cranberry PACs is still lacking. OBJECTIVE: A normal-phase high-performance liquid chromatography (NP-HPLC) method using relative response factors was developed and validated to quantify cranberry PAC oligomers and polymers. MATERIALS AND METHODS: PAC oligomers with degree of polymerisation (DP) 3-9 and total polymers were isolated from the cranberry juice concentrate. Characterisation of the isolated PAC oligomers was performed by ultra-performance liquid chromatography-high resolution mass spectrometry. The relative response factors of oligomers from DP 2-9 and total polymers were determined against procyanidin A2. Method validation was conducted to assess limit of detection, limit of quantification, the linearity and working range, precision and accuracy. In addition, quantifications of PACs by NP-HPLC using relative response factors and two other commonly used methods were conducted in three cranberry food products. RESULTS: Cranberries PACs oligomers contained both A-type and B-type linkage, with epicatechin and epigallocatechin as basic units. Method validation results suggested this method is reliable and reproducible. Quantifications of PACs by NP-HPLC using relative response factors yielded higher values than that by the other two methods. CONCLUSION: A NP-HPLC method using the relative response factors was developed and validated. This method provides a more accurate approach in determining cranberry PACs. It can be used to quantify individual oligomers from DP 2-9, total polymers and total PACs in cranberries and cranberry products.

Analysis of cranberry proanthocyanidins using UPLC-ion mobility-high-resolution mass spectrometry.

Cranberry proanthocyanidin oligomers were investigated using ultra performance liquid chromatography-ion mobility-high-resolution mass spectrometry (UPLC-IM-HRMS). A total of 304 individual A-type and B-type proanthocyanidins, including 40 trimers, 68 tetramers, 53 pentamers, 54 hexamers, 49 heptamers, 28 octamers, and 12 nonamers, were characterized. A-type proanthocyanidins appeared to dominate the cranberry proanthocyanidins. As the degree of polymerization increased, the abundance of molecules with multiple A-type double inter-flavan linkage or having doubly charged ions also increased. Under the same charge state, the drift times of proanthocyanidin ions increased with their degree of polymerization or the number of double inter-flavan linkages. For the same proanthocyanidin molecules, doubly charged ions had shorter drift times compared to their singly charged counterparts, which lead to separated trendlines in the ion mobility-mass plot. While consistent ion mobility was observed for most proanthocyanidins with the same degree of polymerization, coeluted isomeric ions of trimer and tetramer were detected by their unique drift times. Incorporation of ion mobility into HRMS proved to be of great value to characterize and analyze proanthocyanidins from complex sample matrices. Graphical abstract.

In vitro antioxidant capacity and anti-inflammatory activity of seven common oats.

Oats are gaining increasing scientific and public interest for their purported antioxidant-associated health benefits. Most reported studies focused on specific oat extracts or particular oat components, such as ß-glucans, tocols (vitamin E), or avenanthramides. Studies on whole oats with respect to antioxidant and anti-inflammatory activities are still lacking. Here the antioxidant and anti-inflammatory activities from whole oat groats of seven common varieties were evaluated. All oat varieties had very similar oxygen radical absorption capacity compared with other whole grains. In an anti-inflammatory assay, oat variety CDC Dancer inhibited tumor necrosis factor-α induced nuclear factor-kappa B activation by 27.5% at 2 mg/ml, whereas variety Deiter showed 13.7% inhibition at a comparable dose. Avenanthramide levels did not correlate with the observed antioxidant and anti-inflammatory activities. Further investigations are needed to pinpoint the specific antioxidant and anti-inflammatory compounds, and potential synergistic and/or matrix effects that may help explain the mechanisms of oat's anti-inflammatory actions.