New features of intramolecular copigmentation by acylated anthocyanins

Abstract

Three series of structurally related anthocyanins, extracted from the red–purple flowers of Dendrobium Pramot, xLaeliocattleya cv. Mini Purple, Bletilla striata and Phalaenopsis all belonging to the Orchidaceae family and another series extracted from the pink flowers of Senecio cruentus (Compositae) allowed the confirmation of the existence of strong intramolecular copigmentation effects. These interactions confer stability to the coloured forms of the molecules, in a wide range of slightly acidic to neutral aqueous media. Moreover, the existence of structural relationships among the four series stressed the different influences exerted by the diverse substituent groups. The existence of a malonylglucoside attached to position 3 of all but three of the molecules put forward a new role for the malonyl residue, in this particular position.