Antifungal effects of drimane sesquiterpenoids isolated from Drimys winteri against Gaeumannomyces graminis var. tritici

Gaeumannomyces graminis var. tritici (Ggt) is a soil-borne pathogen which causes 'take-all' disease affecting cereal roots. In wheat, Ggt is the most important biotic factor causing around 30-50% of yield losses. The chemical control of this fungal disease is difficult, due to Ggt is able to reside for a long time in soils. Therefore, the development of biotechnological strategies environmentally friendly to diminish the incidence of soil-borne diseases is highly desirable.Natural products are promissory strategy to biocontrol of plants pathogens. Special emphasis in medicinal plants due their fungitoxic effects have been reported. Drimys winteri (Canelo) is a medicinal plant widely used by the "mapuche" ethnic group from Chile due to its anti-inflammatory activity. In addition, inhibitory effects from canelo against phytopathogenic fungi and pest insects have been reported. In this study, we isolated, purified and identified six compounds of drimane sesquiterpenoid skeleton from canelo (drimenin, drimenol, polygodial, isodrimeninol, valdiviolide and drimendiol). Then, their antimicrobial effect against Ggt was evaluated. Compounds were identified by comparison of FTIR and the retention time by TLC, contrasting with pure standards.The putative antagonistic effects were confirmed by hyphal cell wall damage using confocal microscopy and lipid peroxidation. Here, we reported the high potential of drimane sesquiterpenoids as a natural antifungal against Ggt. Polygodial and isodrimeninol were the more effectives with an activity of LC50 between 7 and 10 μL^-1 and higher fungal lipid peroxidation. Accordingly, natural sesquiterpenoids purified from canelo are biologically active against Ggt and could be used as natural biofungicide to sustainable agriculture.Importance More than two billion tons of pesticides are used every year worldwide. An interesting, sustainable alternative to control plant pathogens is the use of natural products obtained from plants, mainly in the case of medicinal plants that offer important secondary metabolites to human/animal health. In this study, we isolated, identified six pure drimane sesquiterpenoids obtained from barks of Drimys winteri. Additionally, we evaluated their antifungal activity against Gaaeumannomyces graminis, Ggt (the main biotic factor affecting cereal production, especially wheat) by the wall-fungus and lipid peroxidation. Obtained compounds showed important antifungal properties against Ggt, mainly isodrimenol which is the second compound more active before polygodial with an activity against Ggt LC50 around 9.5 ug mL^-1 This information could be useful for the development of new natural or hemi-synthetic antifungal agents against soil-borne phytopathogens which could be used in a green agriculture.