Photoprotection of a Stilbenoid Extract for Downy Mildew Control

Area of Science:

• Agricultural Science
• Plant Pathology
• Biochemistry

Background:

• Stilbenoids are natural compounds in grapes with antimicrobial properties.
• These stilbenoids are effective against grapevine downy mildew (caused by *Plasmopara viticola*).
• UV-A radiation causes photodegradation, reducing stilbenoid efficacy.

Purpose of the Study:

• To enhance the photostability of stilbenoids from grapevine cane extract (CE).
• To maintain the bioactivity of stilbenoids against *P. viticola* post-photoprotection.
• To evaluate strategies for sustainable disease management in viticulture.

Main Methods:

• Investigated encapsulation of CE stilbenoids in cellulose nanocrystal-stabilized emulsions.
• Assessed photostability and photodegradation levels under UV-A exposure.
• Evaluated the biological activity of treated CE against *P. viticola*.
• Tested combinations of CE with flavonoids (hesperidin methyl chalcone, rutin).

Main Results:

• Encapsulation achieved 53% efficiency, reducing photodegradation from 73.9% to 37.5% but diminishing bioactivity.
• Flavonoid combinations improved photostability moderately while preserving significant anti-mildew activity.
• Control samples showed substantial stilbenoid loss (73.9%) after 1 hour of UV-A exposure.

Conclusions:

• Flavonoid co-formulation offers a promising strategy to balance stilbenoid photostability and bioactivity.
• These photoprotection methods support the use of stilbenoid extracts for eco-friendly grape disease management.
• Further research can optimize these approaches for sustainable agriculture.