Collective term for antimicrobial in part oxidation resistant acting 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 may be present, but in a significant amount of plants, they can only be attacked by harmful microorganisms such as bacteria and mushrooms but also in stress conditions like for example UV light or insect infestations. They then quickly accumulate at the site of infection within a few hours. So far, over 12,000 different species have been discovered. in the Rebstock becoming active phytoalexins belong to a group of phenols which are called Stilbene. They arise in infestation by various diseases such as wrong or true mildew and Botrytis in the leaves and berry peels. The spread of the diseases is thereby slowed down or inhibited.
Three common also in the grapevine are contained phytoalexins 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 thus increases the proportion of the necessary antibodies. In red wines is usually about ten times the amount White wines contain, as by the usual maceration much more of these substances from the shells extracted and get into the wine. The phytoalexins in the wine also have a positive, health Effect. They are therefore used in chemotherapy for cancer and as a prevention of heart disease. As part of the pest Management Through targeted transmission of "foreign phytoalexins" on vines an increase of resistance against various diseases. See also below Vine enemies,