Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brasil.
Photochem Photobiol. 2012 Jul-Aug;88(4):928-37. doi: 10.1111/j.1751-1097.2012.01125.x. Epub 2012 Mar 28.
The aim of this study was to determine which anthocyanins are related to the purple coloration of young leaves in Coffea arabica var. Purpurascens and assess their impact on photosynthesis as compared to C. arabica var. Catuaí, with green leaves. Two delphinidin glicosides were identified and histological cross-sections showed they were located throughout the adaxial epidermis in young leaves, disappearing as the leaves mature. Regardless the irradiance level, the photosynthetic performance of Purpurascens leaves did not differ from that observed in leaves of the Catuaí variety, providing no evidence that anthocyanins improve photosynthetic performance in coffee plants. To analyze the photoprotective action of anthocyanins, we evaluated the isomerization process for chlorogenic acids (CGAs) in coffee leaves exposed to UV-B radiation. No differences were observed in the total concentration of phenolic compounds in either variety before or after the UV treatment; however, we observed less degradation of CGA isomers in the Purpurascens leaves and a relative increase of cis-5-caffeoylquinic acid, a positional isomer of one of the most abundant form of CQA in coffee leaves, trans-5-caffeoylquinic acid, suggesting a possible protective role for anthocyanins in this purple coffee variety.
本研究旨在确定与 Coffea arabica var. Purpurascens 幼叶紫色有关的花色苷，并评估其与具有绿色叶片的 C. arabica var. Catuaí 的光合作用相比的影响。鉴定出两种飞燕草素糖苷，组织学横截面显示它们位于幼叶的上表皮中，随着叶片成熟而消失。无论辐照度水平如何，Purpurascens 叶片的光合作用性能都与 Catuaí 品种叶片观察到的没有差异，这表明花色苷不会提高咖啡植物的光合作用性能。为了分析花色苷的光保护作用，我们评估了暴露在 UV-B 辐射下咖啡叶片中绿原酸（CGAs）的异构化过程。在 UV 处理前后，两种品种叶片中总酚类化合物的浓度均无差异；然而，我们观察到 Purpurascens 叶片中 CGA 异构体的降解较少，顺式-5-咖啡酰奎尼酸（一种在咖啡叶片中最丰富的 CQA 形式之一的反式-5-咖啡酰奎尼酸的位置异构体）的相对增加，表明花色苷在这种紫色咖啡品种中可能具有保护作用。
