Sample preparation procyanidins

Reversed-phase HPLC is used for the analysis of the different groups of phenols, phenolic acids, hydroxycinnamic acids, flavonoids, and procyanidins in grapes and wines (22,46,47,77-80). However, due to the presence of a large quantities of various compounds, wine analysis is difficult. Thus, different sample preparation procedures, including fractionation and extraction, are often applied when various groups of phenolic compounds are studied together. 

A major drawback of all functional group assays is that a satisfactory standard does not exist. For a given sample the most appropriate standard is a purified procyanidin fraction prepared from the same matrix. The isolation and characterization of such purified fractions are laborious. Added to that procyanidins undergo oxidation, complexation and self-polymerization very easily, rendering such purified fractions only reproducible to a limited degree. At least in the proanthocyanidin assay the color reaction depends not only on the polyphenols themselves, but also on the matrix. The use of specified proanthocyanidins as a standard in a suitable blank matrix is an attempt to correct for such effects [67],... 

The determination of polyphenolic compounds in biological fluids uses a short column of small diameter and with a small sorbents particle. Serra et al. (30) used an HSS T3 column of a length of 100 mm for the determination of procyanidins and their metabolites in rat plasma samples. Hence, the proposed method allowed the accurate determination of procyanidins and their metaboUtes within 5 min. The same column was used to identify twenty-one procyanidins and anthocyanins in rat plasma samples, after due preparation of samples using p,SPE. The aforementioned methods were also applied by Marti et al. (29). Used by Wang et al., a system consisting of a BEH C18 column with a length of 100 mm at 30°C and a buffer as the mobile phase allowed the determination of isoflavones in plasma of six rats within 6 min (22). 

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