The objective of this study was to investigate the thermodynamic parameters of the copigmentation reaction between three anthocyanins and two copigments: quercetin-5’-sulphonic acid (QSA) and flavones isolated from the roots of Scutellaria baicalensis Georgi and also to determine the factors that affected the reaction, while defining its thermodynamic parameters. The interactions of these molecules were observed via UV-VIS absorption spectroscopy. It was established that the pH and temperature affected the copigmentation process. The negative change of entropy, ΔS, as a measure of system ordering, is also a proof of copigment formation, under given condition. Our result indicates that the QSA formed the most stable complex with great affinity and system ordering. Comparing the obtained characteristics of QSA with flavones, it can be concluded that with QSA, where the affinity is lower, a more stable copigment is formed than in the case of flavones, were the situation is inverted. Temperature appears to be the basic parameter of the thermodynamic feasibility of the process, since the copigmentation process is exothermic and spontaneous.

57-65