In this project, researchers aimed to synthesize oligomeric stilbenes from natural resveratrol by oxidative coupling using metals. Stilbenes are produced by grapevine plants, in response to stress conditions, such as when exposed to pathogens. Stilbene or resveratrol oligomers are synthesized by vines to act as the active compounds that have anti-microbial properties to inhibit pathogen growth in grapevine defence systems.
Even though resveratrol is plentiful in grapevine canes or other natural sources, obtaining enough raw material for the effective production of large volumes of oligomers to be used in crop protection could be challenging. Some studies have reported that oligomeric stilbenes can however be produced from resveratrol hemisynthesis using metals, this knowledge formed the basis of this study.
Project layout
- Resveratrol was extracted and purified from grapevine cane extract.
- Oxidative coupling of resveratrol was conducted in methanol using silver acetate as catalyst.
- The anti-microbial efficacy of the resulting stilbene solution against downy mildew and Botrytis was tested in a laboratory.
- For comparison, the stilbene solution, resveratrol and grapevine cane extract were all used in the tests.
Refer to article for more specific details about the chemical processes.
Results
- Four purified oligomeric compounds were successfully produced from resveratrol with δ‑viniferin being the main one.
- The stilbene reaction mixture completely inhibited downy mildew development.Grapevine cane extract also completely inhibited downy mildew, but much higher concentrations of extract was needed to achieve control.
- The stilbene reaction mixture completely inhibited Botrytis development.
- Grapevine cane extract was only moderately effective against Botrytis.
Significance of the study
Chemical treatment of crops are increasingly under pressure. Finding alternative biocontrol methods are becoming more and more critical. Development of resistant varieties are a long process and consumer acceptance of unknown, new varieties are uncertain.
This project indicated that the process used in the study successfully produced antimicrobial compounds from natural resveratrol. It could be a way to not only add value to grapevine by-products, but also provides a potential alternative to chemical control of diseases. Whether the process can be replicated on a large commercial scale and achieve the same results in field trials, will require additional research, product development and trials.
Ideally, the process of extracting and reusing the compounds used in the reaction process (such as the metals) also need to be refined.
Reference
El Khawand T., Gabaston J., Taillis D., Iglesias M.-L., Pedrot E., Palos Pinto A., Valls Fonayet J., Merillon J.M., Decendit A., Cluzet S., & Richard T. (2020). A dimeric stilbene extract produced by oxidative coupling of resveratrol active against Plasmopara viticola and Botrytis cinerea for vine treatments: This article is published in cooperation with the 11th OenoIVAS International Symposium, June 25–28 2019, Bordeaux, France. OENO One, 54(1), 157-164. https://doi.org/10.20870/oeno-one.2020.54.1.2529
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