Chemistry Inspired by the Colors of Fruits, Flowers and Wine

ABSTRACT An overview is provided of the status of research at the frontiers of investigation of the chemistry and photochemistry of two classes of natural plant pigments, the anthocyanins and the betalains, as well as of the pyranoanthocyanin pigments formed from anthocyanins during the maturation of red wine. Together, anthocyanins and betalains are responsible for almost all of the red, purple and blue colors of fruits and flowers and anthocyanins and pyranoanthocyanins are major contributors to the color of red wines. All three types of pigments are cationic below about pH 3, highly colored, non-toxic, reasonably soluble in water or alcohol and fairly stable to light. They exhibit good antioxidant or antiradical activity and, as part of our diet, confer a number of important health benefits. Systematic studies of model compounds containing the basic chromophoric groups of these three types of pigments are providing a deeper understanding of the often complex chemistry and photochemistry of these pigments and their relationship to the roles in vivo of these pigments in plants. These natural pigments are currently being exploited as starting materials for the preparation of novel semi-synthetic dyes, pigments and fluorescence probes.

摘要：本综述梳理了两类天然植物色素——花青素(anthocyanins)与甜菜红素(betalains)，以及红酒陈酿过程中由花青素生成的吡喃花青素(pyranoanthocyanins)的化学与光化学研究前沿现状。花青素与甜菜红素共同构成了果蔬、花卉中绝大多数红、紫、蓝色调的来源；而花青素与吡喃花青素则是红酒色泽的主要成因。上述三类色素在pH约3以下均呈阳离子态，色泽浓郁、无毒、可较好地溶于水或乙醇，且对光照具备良好稳定性。它们拥有优异的抗氧化或抗自由基活性，作为日常膳食的组成部分，可为人体带来诸多重要健康益处。针对携带有这三类色素核心生色基团的模型化合物开展的系统研究，正逐步深化学界对这类色素往往较为复杂的化学与光化学过程，以及其与这些色素在植物体内生理功能间关联的认知。目前，这类天然色素正被用作制备新型半合成染料、色素及荧光探针的起始原料。