Abstract
Aim: Stilbenes are a group of polyphenols that contribute to the defense mechanisms of grapevine under stress conditions. The main active compounds are oligomeric stilbenes. The sourcing of such compounds is limited by plant raw material availability. In order to overcome this limitation, we proceeded to hemisynthesis of oligomeric stilbenes from natural resveratrol by oxidative coupling using metals. The reaction mixture and the obtained pure compounds were tested for their antimicrobial activity in vitro against P. viticola and B. cinerea, and compared with that of resveratrol and grapevine cane extract.Methods and results: Hemisynthesis was achieved in methanol using silver acetate (AgOAc) as oxidative coupling reagent. Four main compounds were obtained in the reaction mixture: δ-viniferin, parthenostilbenin B, oxistilbenins A and B. Results demonstrate the ability of oxidative coupling reaction to produce potent inhibitors of P. viticola and B. cinerea. The reaction mixture is enriched in antimicrobial compounds with high potency as it is at least eight times more active than grapevine cane extract against P. viticola. In addition, this reaction mixture reveals a high fungitoxicity against B. cinerea in contrast to the grapevine extract.Conclusion: The present findings indicate that metals could be used for producing highly antimicrobial compounds from natural resveratrol.Significance and impact of the study: In this study, a method to produce active dimeric stilbenes to protect grapevine was developed based on botanical ingredients. The combination of natural extracts, rich in resveratrol, and metals such as copper may be used as alternatives to Bordeaux mixture and chemical fungicides to protect crops.
Highlights
The use of chemical pesticides to protect crops is increasingly called into question nowadays, due to their damaging impact on human and ecosystems health
This problem is subject to much debate in winegrowing regions, where Vitis vinifera grapes and wine production depends on pesticides used to control grapevine microbial diseases
Alternative preventive or curative solutions are necessary in order to achieve the reduction of pesticides use and to ensure the stability of wine production and economy worldwide
Summary
The use of chemical pesticides to protect crops is increasingly called into question nowadays, due to their damaging impact on human and ecosystems health. This problem is subject to much debate in winegrowing regions, where Vitis vinifera grapes and wine production depends on pesticides used to control grapevine microbial diseases. Oligomers of resveratrol, such as viniferins, are promising antimicrobial compounds (Gabaston et al, 2017) Even if these compounds are present grapevine byproducts (Gabaston et al, 2019), oligomeric stilbenes sourcing could be problematic in case of large-scale use such as crop treatment
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