Characterization of stilbenoids from the stem bark of Norway spruce (Picea abies) as antifungal agents
14 December 2016 (online)
The oomycete Plasmopara viticola is the cause of downy mildew that is one of the most economically important diseases of cultivated grapevines worldwide.1 Today the damage caused by downy mildew has generally been controlled using multiple fungicide applications [1,2]. Henceforth there is renewed interest in search for effective ecofriendly and sustainable natural agents to control diseases and pests because of changes in environment and food safety regulations associated with consumer demand. In this objective, antifungal activity against downy mildew of spruce bark (Picea abies) extract, rich in stilbenes,  was investigated. These phenolic compounds with a diaryl-ethylene skeleton are known to have antifungal properties and to contribute to plant disease resistance . The analysis of the extract using UHPLC-MS allowed to targeted stilbenes as main components. The structure of stilbenes isolated from the hydro-alcoholic extract by preparative HPLC was determined by 1D and 2D NMR. In addition to aglycone and glycosylated monomeric forms, such as piceatannol, astringin, resveratrol, piceid, isorhapontigenin and isorhapontin, several stilbene glycoside dimers were also identified. Some of these compounds were reported for the first time in plant kingdom. The extract showed significant antifungal activity with an inhibition of the conidia germination and mycelium growth of P. viticola. Our results show that spruce bark extract, considered as wood industry co-product, have a potential development as natural fungicide against downy mildew.
Acknowledgements: Eric Pedrot and Marie-Laure Iglesias are acknowledged for technical assistance.
Keywords: Norway spruce, Picea abies, stilbene, natural fungicide, downy mildew.
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