Tannins molecular size

The purity of each fraction obtained with these separation methods and the isolated tannins may be monitored by means of analytical HPLC in normal phase and reversed-phase modes under the conditions outlined in Table 2. The molecular sizes of hydrolyzable tannins can be estimated by normal phase HPLC and, as retention time increases, rank in the order of monomer—>dimer—>trimer—>tetramer as seen in Fig. 1. 

Polyphenols (syn vegetable tannins - proanthocya-nidins and esters of gallic acid, vide supra) constitute one of the most distinctive groups of higher plant secondary metabolites. Their uniqueness lies not only in their molecular size and polyphenolic character but also in their ability to complex strongly with proteins, carbohydrates, nucleic acids and alkaloids. Studies of these properties are not only of intrinsic scientific interest. a scientist who confesses to an interest in polyphenols is invariably asked one question - why do plants form them ... 

Despite these advances, it is generally accepted that the vast majority of die observed color in aged red wine remains to be characterized. The obvious factor that separates characterized compounds from uncharacterized compounds appears to be molecular weight, with much of the high molecular weight material being unknown in structure. What is apparent is that as wine ages, the observed red color increases in size, apparently due to interaction between anthocyanins and proanthocyanidins (tannin) (10). 

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