No abstract

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

Candida species cause an opportunistic yeast infection called Candidiasis, which is responsible for more than 50,000 deaths every year around the world. Effective treatments against candidiasis caused by non-albicans Candida species such as C. glabrata, C. parapsilosis, C. aureus, and C. krusei are limited due to severe resistance to conventional antifungal drugs. Natural drimane sesquiterpenoids have shown promising antifungal properties against Candida yeast and have emerged as valuable candidates for developing new candidiasis therapies. In this work, we isolated isodrimeninol (C1) from barks of Drimys winteri and used it as starting material for the hemi-synthesis of four sesquiterpenoids by oxidation with pyridinium chlorochromate (PCC). The structure of the products (C2, C3, C4, and C5) was elucidated by 1D and 2D NMR spectroscopy resulting in C4 being a novel compound. Antifungal activity assays against C. albicans, C. glabrata, and C. krusei revealed that C4 exhibited an increased activity (IC50 of 75 μg/mL) compared to C1 (IC50 of 125 μg/mL) in all yeast strains. The antifungal activity of C1 and C4 was rationalized in terms of their capability to inhibit lanosterol 14-alpha demethylase using molecular docking, molecular dynamics simulations, and MM/GBSA binding free energy calculations. In silico analysis revealed that C1 and C4 bind to the outermost region of the catalytic site of 14-alpha demethylase and block the entrance of lanosterol (LAN) to the catalytic pocket. Binding free energy estimates suggested that C4 forms a more stable complex with the enzyme than C1, in agreement with the experimental evidence. Based on this new approach it is possible to design new drimane-type sesquiterpenoids for the control of Candida species as inhibitors of 14-alpha demethylase.