GRAPE ANTHOCYANINS (Vitis vinifera L.) AND THEIR RELATION TO COLOR

Abstract

Anthocyanins are phenolic compounds, mainly found in fruits, leaves and flowers, where they confer the red, blue and violet colors. They are synthesized from active precursors: phenil alanine and acetate by the propanoid pathway, and are accumulated into hypodermal vacuoles. The enzymes of this biosynthetic pathway are regulated at the transcriptional level. The gene encoding for UDP-glucose: flavon-oid 3-glucosyltransferase (UFGT), the last step in the biosynthetic pathway, is critical for anthocyanin synthesis in grape berry skins. Anthocyanins are synthesized during veraisson and are the most important pigments in red and colored grapes. Their structure is heteroside made by the combination of an aglycon and a sugar, usually glucose. In Vitis vinifera cultivars, sugar are fixed in position 3; however, other Vitis species have two glucosides. Anthocyanins are the most powerful natural antioxidants; and their study has been difficult because of their unstability. However, they can be stabilized by acylation, and then they may be efficiently stored by vacuoles. In general, their role is associated to render color in berries and to detoxification under light stressing conditions, so their study is important. The concentration and anthocyanin profile varies among grape species, cultivars, maturity stages, seasons, environmental conditions, field practices and levels of yield. Light and temperature are the main environmental variables that regulate their biosynthesis where light stimulates it and high temperature appears to inhibit it. This review aims to address recent advances on the anthocyanin nature, regulation of biosynthetic pathway, and their relation to luminosity and temperature in grapes.