Z-chalcone

Houbiers, C. et al.. Color stabilization of malvidin 3-glucoside self-aggregation on the of flavylium cation and copigmentation with the Z-chalcone form, J. Phys. Chem. B, 102, 3578, 1998. 

Absorption spectra have also been used in the reexamination of pH-dependent color and structural transformations in aqueous solutions of some nonacylated anthocyanins and synthetic flavylium salts." ° In a recent study, the UV-Vis spectra of flower extracts of Hibiscus rosasinensis have been measured between 240 and 748 nm at pH values ranging from 1.1 to 13.0." Deconvolution of these spectra using the parallel factor analysis (PARAFAC) model permitted the study of anthocyanin systems without isolation and purification of the individual species (Figure 2.21). The model allowed identification of seven anthocyanin equilibrium forms, namely the flavylium cation, carbinol, quinoidal base, and E- and Z-chalcone and their ionized forms, as well as their relative concentrations as a function of pH. The spectral profiles recovered were in agreement with previous models of equilibrium forms reported in literature, based on studies of pure pigments. 

George, E., Eigueiredo, P., and Brouillard, R. Malvin Z-chalcone an unexpected new open cavity for the ferric cation. Phytochemistry, 50, 1391, 1999. 

Z-Chalcones unexpected open cavities for the ferric cation... 

Fig. 1.5 The flexible open cavity of the malvin Z-chalcone best fits the steric and electronic requirements of...

Fig. 1.6 H NMR spectra of malvin chloride at 25 °C (a) pure malvin chloride, (b) malvin with ferric chloride after 1 h, and (c) at equilibrium after a full day. Symbols indicate the different forms (see Fig. 1.3) ( ) flavylium cation, ( /°) hemiketal, (A) 5-retrochalcone, ( ) Z-retrochalcone, and ( ) Z-chalcone-iron complex.

The recent discovery that Z-retrochalcones (natural anthocyanin retrochalcones) encapsulate iron (III) points out that they can play a nutritional role. Owing to this property, anthocyanins may take part in the uptake and regulation of this vital metal in the human body. If it is the case, it would be wise to consume red fruits (edible berries) with good amounts of structurally simple glycosylated anthocyanins whose Z-chalcones are perfectly sized for complexing iron (III). 

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