Unexpected hyperchromic interactions during the chromatography of theafulvins and simple flavonoids

Theafulvins, isolated from black tea, chromatograph as a hump on reversed p hase column packings. When whole black-tea brews are similarly analysed oth er phenolic compounds appear as more or less resolved peaks 'floating' on t his hump. Model solutions of isolated theafulvins containing individual pur e compounds (flavanols, flavonols and caffeine) have been prepared and thei r chromatographic behaviour compared with that of the pure compound chromat ographed alone. In the case of quercetin, epicatechin and epicatechin galla te, a statistically significant hyperchromic effect has been observed in wh ich the peak area 'floating' on top of the theafulvin hump is larger than e xpected from the area obtained for the pure compound alone. There was littl e or no effect with catechin and caffeine, and rutin showed a weak and inco nsistent response. The data are discussed by reference to the established l iterature on copigmentation but it is not possible to define the mechanism responsible for the hyperchromism at this stage. (C) 1999 Elsevier Science Lsd. All rights reserved.