Multi-laboratory validation of a standard method for quantifying proanthocyanidins in cranberry powders.

Background: The objective of this study was to validate an improved 4-dimethylaminocinnamaldehyde (DMAC) colorimetric method using a commercially available standard (procyanidin A2), for the standard method for quantification of proanthocyanidins (PACs) in cranberry powders, in order to establish dosage guidelines for the uropathogenic bacterial anti-adhesion effect of cranberry.

Results: Commercially available cranberry samples were obtained (five from U.S.