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.

The objective of this study was to develop a thiolysis HPLC method to quantify total procyanidins, the ratio of A-type linkages, and A-type procyanidin equivalents in cranberry products. Cysteamine was utilized as a low-odor substitute of toluene-α-thiol for thiolysis depolymerization. A reaction temperature of 70 °C and reaction time of 20 min, in 0.3 M of HCl, were determined to be optimum depolymerization conditions. Thiolytic products of cranberry procyanidins were separated by RP-HPLC and identified using high-resolution mass spectrometry. Standards curves of good linearity were obtained on thiolyzed procyanidin dimer A2 and B2 external standards. The detection and quantification limits, recovery, and precision of this method were validated. The new method was applied to quantitate total procyanidins, average degree of polymerization, ratio of A-type linkages, and A-type procyanidin equivalents in cranberry products. Results showed that the method was suitable for quantitative and qualitative analysis of procyanidins in cranberry products.

American cranberry (Vaccinium macrocarpon) is native to Eastern North America. Recent studies have suggested that the A-type proanthocyanidins (PACs) in cranberries are effective in preventing urinary tract infection. To meet the growing interest in the cranberry market, an accurate, reliable, and simple method to determine PAC concentration is needed. In this study, a modified method using 4-dimethylaminocinnamaldehyde to quantify total PACs in cranberry products was validated. Cranberry juice extract powder, cranberry capsules containing juice extract, and cranberry juice concentrate were used as the samples in this study. With the modified method, the calibration curves for proanthocyanidin A2 had correlation coefficients (r(2)) of >0.99. The recoveries of two different concentrations after spiking were 97.1 and 99.1%, and the RSDs for repeatability and reproducibility were <2.7 and <1.6%, respectively.

Cranberry proanthocyanidins (PACs) were characterised by HPLC (after thiolysis) and LC–ESI-MS analysis after fractionation by normal-phase chromatography. According to the HPLC retention time and mass spectra of compounds released after depolymerisation reaction, PACs are based on epicatechin and dimer A2 units along with catechin (minor component) and epigallocatechin (trace amounts). Fractionation at semi-preparative scale on normal phase allowed to remove other phenolic compounds than PACs (flavonols, phenolic acids and anthocyanins) and to separate the PACs according to their polymerisation degrees. Six fractions were eluted. PAC concentration, mean degree of polymerisation and percentage of A-type bonds were calculated for these six fractions by HPLC after thiolysis. Whereas the three first fractions contained phenolic acids and flavonols, the three latest fractions were enriched in PACs. Genuine PACs (A and B-types) from DP2 to DP16 were detected by LC–DAD-ESI-MS analysis. Fragmentation on ion trap spectrometer allowed us to determine the position of A-type bonds. Derived PACs were also observed: anthocyanin ethyl-bridged PACs (monomer to tetramer) in the three last fractions, flavonol-ethyl-PACs (monomer and dimer) in the third fraction and pyranoanthocyanin derivatives in the last fraction.

The American cranberry, Vaccinium macrocarpon Aiton, is a fruit with a number of unique and desirable attributes that has found its way into a wide variety of food products. In addition to its growing reputation as a healthy fruit, cranberries are known for their distinctive taste and color. Whereas the taste of cranberries is highly acidic and consumer preference testing has necessitated the development of products with adjusted Brix to acid ratios, the crimson red color of cranberries is naturally appealing, from their aesthetics in the field to when they are finally consumed. Next to crop yield, fruit color is the attribute paid most attention to by growers. Growers strive to grow and deliver fruit with high color, while handlers and processors strive to manage fruit inventory and processing to optimize color usage in their products. The recent development and popularity with consumers of white cranberry juice beverages has introduced additional and entirely new challenges to cranberry growers, handlers and processors. This chapter will discuss grower, handler and processor practices that enable the delivery of cranberry products with high and consistent color quality to consumers.

The polymeric procyanidins were fractionated from lowbush blueberry on a Sephadex LH-20 column. The degree of polymerization (DP) for the polymers was determined by thiolysis to be in a range of 19.9 to 114.1. Normal-phase HPLC analysis indicated that the polymeric procyanidins did not contain oligomeric procyanidins with DP < 10. The polymers eluted as a single peak at the end of the chromatogram. The normal-phase HPLC gradient was modified to improve the separation of procyanidin monomers through decamers and to elute all the polymers beyond those as a distinct peak. Monomers through decamers were quantified individually. All the polymers (DP > 10) were quantified using a mixture of purified polymers as an external standard. Polymers were found to be the dominant procyanidins in brown sorghum bran, cranberry, and blueberry. Thiolysis of the polymer peaks indicated that epicatechin was present as extension units in these foods, however, the composition of terminal units varied considerably between catechin and epicatechin, or an A-type dimer linkage in the case of cranberry.