Collective name for antimicrobial in part oxidation resistant active chemical compounds that are formed in plants as a defense reaction. The name comes from Phyto (plant) and Alexin (defense). In principle, host-specific phytoalexins can be present, but are only used in significant quantities by plants if they are attacked by harmful microorganisms such as bacteria and mushrooms, but also under stress conditions such as UV light or insect infestation. They quickly accumulate at the infection site within a few hours. So far over 12,000 different species have been discovered. in the Rebstock Effective phytoalexins belong to a group of phenols that are called stilbenes. They are caused by various diseases such as the wrong or the real mildew and Botrytis in the leaves and berry shells. The spread of the diseases is slowed down or inhibited.
Three common ones in the grapevine contained phytoalexins are catechin. resveratrol and viniferine, The concentration of these substances in the wine depends on vine. climate, Cultivation method and winemaking, In cool and humid areas, the risk of disease is greater and the proportion of the necessary defense substances increases. In red wines is usually compared to ten times the amount White wines included since by the usual maceration much more of these substances from the shells extracted and get into the wine. The phytoalexins contained in the wine also have a positive, health Effect. They are therefore used in chemotherapy for cancer and as a prevention against heart diseases. As part of the pest Management can be increased by targeted transfer of "foreign phytoalexins" to vines resistance against various diseases. See also under Vine enemies,