Resveratrol is antioxidant naturally occurring in wine grapes. It is thought to have a preventive biological activity against number of diseases. However, it has been recently shown that in the presence of metal ions, such as Cu2+, resveratrol forms oxidative radicals. Cu2+ is usually present in wine due to former usage of bluestone in vineyards. Fungicide tebuconazole has substituted bluestone and is presently one of the most widely used agrochemicals in wine industry; wine thus may contain traces of tebuconazole. Here, we study the ternary system of resveratrol, Cu2+, and tebuconazole experimentally and theoretically (using mass spectrometry, antioxidant capacity assay and quantum-chemical calculations) to model the redox behaviour of resveratrol in wine. We show that tebuconazole prevents formation of oxidative resveratrol radicals (induced by Cu2+ reaction with resveratrol) via preferential Cu2+ capture and protection of the binding sites of resveratrol. This positive effect of tebuconazole has not been observed before.

Department of Agro Environmental Chemistry and Plant Nutrition Faculty of Agrobiology Food and Natural Resources Czech University of Life Sciences Prague Kamýcká 129 165 00 Prague Suchdol Czech Republic

Department of Biochemistry Faculty of Science Charles University Hlavova 2030 128 43 Praha 2 Czech Republic

Institute of Organic Chemistry and Biochemistry The Czech Academy of Sciences Flemingovo náměstí 2 166 10 Prague 6 Czech Republic

Institute of Organic Chemistry and Biochemistry The Czech Academy of Sciences Flemingovo náměstí 2 166 10 Prague 6 Czech Republic; Department of Physiology and Biochemistry Faculty of Physical Education and Sport Charles University Jose Martího 31 162 52 Prague 6 Czech Republic

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