METHOD TO DETERMINE RESVERATROL AND PTEROSTILBENE IN GRAPE BERRIES AND WINES USING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AND HIGHLY SENSITIVE FLUOROMETRIC DETECTION

Resveratrol and pterostilbene are two hydroxystilbenic phytoalexins synthesized by Vitaceae. Produced by leaves and grape berries after biotic or abiotic stress, the determination of their concentration can help to evaluate the disease resistance of different vine varieties. Resveratrol is also found in wines, particularly in red wine. These stilbenes are highly sensitive to light and air oxidation. Extraction must be made under nitrogen and protected from light. HPLC separation of resveratrol and pterostilbene is performed on a reversed phase (C-18) with a methanol-formic acid (50 mM) gradient. Fluorimetric detection is much more sensitive than UV detection and its specificity allows simple pre-purification of grape berries and direct injection of wines.