Grape skin infection, response

The green grape skin is also capable of synthesizing phytoalexins in response to an infection (Langcake and Pryce, 1977). These stilbenic derivatives (trans-resveratrol and its glycoside, trans-piceid, dimer e-viniferin, a-viniferin trimer, /S-viniferin tetramer) have fungicidal properties (Figure 10.24). 

One of the most relevant and extensively studied stilbene is trani-resveratrol (3,5,4 -trihydroxystilbene), a phytoalexin produced by grapevines in response to fungal infection, particularly Botrytis cinerea. Synthesis of resveratrol in grape berries is mainly located in the skin cells and is absent or low in the fruit flesh. In nature, resveratrol exists in two isomeric forms (cis- and frani -conflgured) in the free as well as in 6-glucoconjugated form. The 3-0-6-D-glucosides of cis- and trans-resveratrol cis-and trans-conflgured are called piceids. The chemical structures of resveratrol and further stilbenes are depicted in Fig. 9C.6. 

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