The proanthocyanidin (PAC) content of foods is reported in nutrient databanks, and increased PAC consumption is associated with reduced risk of some chronic diseases. PACs are typically quantified using normal phase HPLC separating based on the number of flavan-3-ol monomeric units, usually up to degree of polymerization (DP) 10, with absorbance or fluorescence detection. Given the lack of authentic standards, most nutrient databank values are quantitated using cocoa or blueberry standards or using (+)-catechin as a standard correcting by DP using detector response factors originally calculated using blueberry and cocoa standards. The objective of this study was to determine the extent to which detector response depends on PAC composition. To get a diverse representation of flavan-3-ol constituents with varying levels of galloylation and both single and double linkages between monomeric units, PACs were extracted from cocoa, blueberries, green grapes, kidney beans, and cinnamon. Extracts were purified using Sephadex LH-20 gel permeation chromatography and quantified using HILIC HPLC with absorbance and fluorescence detection. Quantitation of PACs as (+)-catechin equivalents by absorbance resulted in higher values than using fluorescence for all PACs except the monomers of green grapes, kidney beans, and blueberries. For example, kidney beans differed by a factor of 1.1 (±0.1 standard deviation) for monomers and 9 (± 2 standard deviation) for polymers of DP &gt; 10. The detector response factors were variable between foods, DP, and detection method and differed from prior reports by over an order of magnitude. Therefore, quantitation of PACs as (+)-catechin equivalents with DP response factors or utilizing non-authentic external standards may misrepresent the PAC content. Given the extent of diversity in PAC detector responses, the use of authentic standards for each PAC DP and food type is expected to improve quantitation accuracy.

Dietary proanthocyanidin detector response factors have appreciable variability

253rd National Meeting (2017)

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