Inhibitory potential of bioactive extracts from southern Brazil mushrooms on the pathogenic oomycete Pythium insidiosum

Pythium insidiosum is an important oomycete pathogen of mammals that causes pythiosis, an endemic disease in warm climates that stands out for its unfavorable prognosis, lethality in the affected species, and difficulties in treatment. This study evaluated in vitro anti-P . insidiosum potential of aqueous, hydroethanolic, and ethanolic extracts of indigenous wild mushrooms from southern Brazil. The extracts were prepared from Amanita gemmata , Amanita muscaria , Auricularia auricula , Gymnopilus junonius , Lactarius deliciosus , Laccaria laccata , Psilocybe cubensis , and Russula xerampelina. In vitro susceptibility assays employed the microdilution technique according to the M38-A2 protocol CLSI . The hydroethanolic and ethanolic extracts of R. xerampelina showed anti- P. insidiosum activity at minimum inhibitory concentrations ranging from 1.87-7.50 mg/mL. The other mushroom species extracts showed no inhibitory effects on growth of P. insidiosum . This is the first study to evaluate the antimicrobial activity of mushrooms on oomycetes, evidencing the antimicrobial potential of R. xerampelina on the pathogen P. insidiosum. So, the present study expands new perspectives, since the secondary metabolites produced by mushrooms can be potential targets for the development of new categories of medicines. However, considering the wide biodiversity of Brazilian mushrooms, we suggested that the search for other basidiomycetes species with anti- P. insidiosum action needs to be expanded.