The biochemistry and medical significance of the flavonoids.

Copigmentation is a solution phenomenon in which pigments and other noncolored organic components form molecular associations or complexes. It generally results in an enhancement in the absorbance and in some cases, a shift in the wavelength of the maximum absorbance of the pigment. Copigmentation has not previously been taken into account in traditional wine color measures, in the relationship between color and pigment analysis, or in spectrophotometric assays for anthocyanin content. It is now apparent that copigmentation can account for between 30 and 50% of the color in young wines and that it is primarily influenced by the levels of several specific, noncolored phenolic components or cofactors. Copigmentation is of critical importance in understanding the relationship between grape composition and wine color, the variation in color and pigment concentration between wines, and in all reactions involving the anthocyanins during wine aging. This review focuses on the importance of the individual pigments and cofactors, the strength of their interactions, and their relative abundance in grapes and wines. A simple mathematical analysis of the solution equilibrium is developed to explain the nonlinear deviation from Beer’s law. When solved for typical wines, this function provides estimates of the apparent association constant, K, and the apparent molar extinction of the copigmented form, Ec, in natural mixtures. These measures allow the fraction of the anthocyanins which is in the copigmented form to be estimated. The significance of this phenomenon on pigment extraction and color retention during fermentations, on the rate of subsequent pigment polymerization, on the possible protection of anthocyanins from oxidation, and in the possible involvement on perceived mouthfeel and astringency of wines are suggested. Aspects of the copigmentation phenomenon that are poorly understood are identified and some research directions are suggested.

The copigmentation of anthocyanins and its role in the color of red wine: A critical review

Non-thermal stabilization mechanisms of anthocyanins in model and food systems—An overview

Red and black are the most common colors of bird-dispersed fruits in all regions of the world for which information is available; other colors occur, but at lower frequencies. We present 13 nonexclusive hypotheses that may contribute to the observed frequency distribution of fruit colors and assess them, in a preliminary way, using existing information. Five hypotheses relate fruit colors directly to avian foraging: (1) birds prefer red and black (weak support at best); (2) red and black displays are more readily discovered by foraging birds (mixed evidence); (3) fruit colors indicate fruit maturity (mixed evidence); (4) fruit colors facilitate quick recognition of food (little evidence); (5) nutritionally poor fruits mimic nutrient-rich fruits (no data). Three hypotheses relate fruit colors to defense against natural enemies: (6) red fruits are inconspicuous to fruit-foraging arthropods (limited applicability); (7) fruit colors exclude poor dispersal agents (few data); (8) fruit pigments defend fruits ag...

The Evolution of Fruit Color in Fleshy-Fruited Plants

Flower colour results from the preferential absorption of part of the visible light by one, or several, chemical compound(s) synthesized by higher plants. Since plants cannot ‘see’ their own colours, it is conceivable that the colour signals emerging from flowers are messages interpretable by mammals as well as by birds and insects (Harborne, 1976). Thus colour is most likely a link between animals and plants, as are flower shape, scent and taste. In particular, insects and birds attracted by colour pollinate the flowers and aid the survival of plant species. In contrast to man, some insects, especially bees, can perceive in the near ultraviolet (340–380 nm) as well as in the visible.

Lao-Jer Chen

Papers

Structural aspects of anthocyanin-flavonoid complex formation and its role in plant color