Chemical composition and antifungal activity of plant extracts traditionally used in organic and biodynamic farming

Five plant extracts traditionally used in organic and biodynamic farming for pest control and antifungal (downy mildew) disease management were selected after a farmer survey and analyzed for their chemical composition in LC-PDA-MS-MS and using adapted analytical method from food chemistry for determination of class of component (e.g., protein, sugar, lipids...). Their antifungal activity against Penicillium expansum, Botrytis cinerea, Botrytis allii, brown rot causing agents (Monilinia laxa and Monilinia fructigena), and grape downy mildew (Plasmopara viticola) was examined in vitro. White willow (Salix alba) and absinthe (Artemisia absinthium) ethanolic extracts were found to be the most effective in particular against Plasmopara viticola, with a total inhibition of spores germination when applied at 1000mg/L. These extracts also showed a relatively low toxicity during preliminary ecotoxicological assays on Daphnia pulex. Extract from the bark of white willow contained some flavonoids, especially flavanones (eriodyctiol and derivates) and flavanols (catechins and derivates), as major compounds, whereas absinthe extract was rich in O-methylated flavanols and hydroxycinnamic acids. Thujone content in this extract was also determined by external calibration in GC-MS analysis, and its value was 0.004% dry extract.