Alcoholic extracts of Russian sage (Salvia yangii) contain bioactive terpenoids with inhibitory activity against grapevine downy mildew (Plasmopara viticola)

Background: Plant extracts are promising eco-friendly alternatives to synthetic fungicides for developing sustainable plant protection strategies. Grapevine downy mildew, caused by Plasmopara viticola, is a devastating disease that requires frequent fungicide applications, making it an ideal target for plant-based products. Salvia officinalis extracts are known to reduce downy mildew severity, but little is known about the efficacy and chemical composition of other fast-growing Salvia species with low economic value. This study aimed to evaluate the efficacy of alcoholic extracts of Russian sage (Salvia yangii) against grapevine downy mildew and to annotate bioactive compounds against P. viticola. Results: Alcoholic extracts from flowers, leaves, and shoots of Russian sage decreased downy mildew severity on grapevine leaf disks. In particular, leaf and flower extracts showed efficacy comparable to that of copper-based fungicides, whereas stem extract was only partially active. Shoot extracts were fractionated by preparative liquid chromatography (LC), and the activity of the resulting fractions was assessed against P. viticola using leaf disk assays. Untargeted metabolomic analyses revealed putative terpenoids as the main components of the active fractions, as determined by gas chromatography-mass spectrometry (GC-MS) and ultra-high-pressure liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) analyses. Specifically, 7-methylrosmanol, 12-O-methylcarnosic acid, carnosic acid, and carnosol were identified as the main bioactive compounds against P. viticola. Conclusion: Russian sage represents a valuable source of bioactive compounds for sustainable plant protection