Delta-viniferin is a resveratrol dehydrodimer, an isomer of epsilon-viniferin. This compound has been reported as a molecule produced in vitro by the oxidative dimerization of resveratrol by plant peroxidases or fungal laccases. It was also recently identified in wines and in grape cell cultures. We have now identified this dimer by NMR, high-performance liquid chromatography-diode array detection (HPLC-DAD), and HPLC-mass spectrometry (MS) in grapevine leaves infected by Plasmopara viticola (downy mildew) or UV-C irradiated. Its concentration was higher than that of epsilon-viniferin and constitutes one of the most important phytoalexins derived from resveratrol.

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Pterostilbene is a known phytoalexin produced by the Vitaceae. It was identified in the grape berries of Vitis vinifera (var. Gamay and Pinot). Its mode of action on conidia of Botrytis cinerea is a rapid destruction of ribosomes, endoplasmic reticulum, and of mitochondrial and nuclear membrane. Plasma membrane is completely disorganized in three hours. Respiration of the conidia is totally inhibited ten minutes after the addition of the phytoalexin. The physico‐chemical properties ofpterostilbene and the ultrastructural observations of its effects show that this compound could act on membrane proteins and interfere in mitochondrial respiration processes.

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