Viniferins

Viniferins are a class of stilbenoid compounds that are dimers and higher-order oligomers of resveratrol, produced by grapevines (Vitis vinifera) and certain other plants. They arise primarily through oxidative coupling of resveratrol, a reaction that occurs in response to biotic and abiotic stress, including fungal infection and UV exposure. The resulting structures include several isomers and names such as epsilon-viniferin and various ampelopsins (ampelopsin A, B, C, D), among others. These compounds differ in the way the two or more resveratrol units are linked (for example at C8-C8' or other positions).

In grapes, viniferins accumulate in skins and seeds and can be found in wine, although at trace levels compared with resveratrol. Their production is part of the plant's stilbene-based defense system, regulated by stilbene synthase and responsive to pathogen attack (e.g., Plasmopara viticola). Enzymatic oxidation by peroxidases or laccases, as well as radical coupling, can produce viniferins.

Viniferins are polyphenolic compounds with antioxidant capacity; some show anti-inflammatory, antimicrobial, and cytotoxic activities in laboratory studies. The biological relevance in humans at dietary levels is not fully established, and most data derive from in vitro systems or animal models.

Viniferins serve as markers for grape stress responses and are studied for their role in wine chemistry and potential health effects of stilbenoids. Analytical methods detect and quantify viniferins alongside resveratrol.