Anthocyanin anti-copigment effect

By means of visible absorption spectrometry, it is shown that, in aqueous solutions at pH 2 and 25°, callistephin strongly interacts with β-cyclodextrin. The colour loss, or absorption decrease in the visible range, which results from this interaction is mainly due to the encapsulation of callistephin colourless forms into the β-cyclodextrin cavity. This phenomenon, which can lead to an almost complete discoloration if sufficient amounts of the macrocycle are added to callistephin acidic solutions, has been called the anti-copigment effect. The weak interaction taking place between callistephin flavylium cation and β-cyclodextrin cannot oppose the almost selective inclusion of callistephin colourless forms.