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 b rigesii present a distinct feature that sheds new light on the understandin g of intramolecular copigmentation of anthocyanins. These are among the inf requent anthocyanins that naturally present a coumaric acid substituent in both cis and trans forms. As a consequence, the two isomers demonstrate sub stantial variations of their thermodynamic and kinetic constants and also c olour properties. A possible explanation for these characteristics is prese nted, making use of molecular modelling and taking into account the three-d imensional structures of the pigments. (C) 2001 Elsevier Science Ltd. All r ights reserved.