Influence of trans-cis isomerisation of coumaric acid substituents on colour variance and stabilisation in anthocyanins

The recently isolated pigments from Petunia integrifolia and Triteleia br brigesii present a distinct feature that sheds new light on the understanding of intramolecular copigmentation of anthocyanins. These are among the infrequent anthocyanins that naturally present a coumaric acid substituent in both cis and trans forms. As a consequence, the two isomers demonstrate substantial variations of their thermodynamic and kinetic constants and also colour properties. A possible explanation for these characteristics is presented, making use of molecular modelling and taking into account the three-dimensional structures of the pigments. (C) 2001 Elsevier Science Ltd. All rights reserved.