The constant increase of viral resistance and the limited number of effective antiviral agents emphasizes that the current portfolio of anti-influenza drugs needs extension[1]. To identify new anti-influenza agents from nature, locally grown European polypores belonging to the polyphyletic group of Agaricomycetes (Basidiomycota) were collected and identified via rDNA ITS phylogenetic analyses[2]. Fruit bodies from ten species were collected and mycochemically investigated, i.e. Fomes fomentarius, Fomitopsis pinicola, Ganoderma lucidum, G. applanatum, Gloeophyllum odoratum, Ischnoderma benzoinum, Laetiporus sulphureus, Phellinus robustus, Piptoporus betulinus, and Trametes gibbosa. The generated ethanol extracts were screened in a cytopathic effect (CPE) inhibition assay against H3N2 influenza virus A/Hong Kong/68 (HK/68) in MDCK cells. Especially the extract of G. odoratum dose-dependently inhibited the CPE with an IC50 of 15.0 µg/mL[3]. A fluorescence-based neuraminidase (NA) inhibition assay excluded that the antiviral activity was based on the inhibition of the surface protein NA. HRESIMS, 1D and 2D NMR spectroscopy were used for the identification of eight isolated lanostane triterpenes with two novel natural compounds and three undescribed so far for G. odoratum. The most potent activity was determined for trametenolic acid B against HK/68 and the 2009 pandemic H1N1 strain A/Jena/8178/09 with IC50s of 14.1 and 11.3 µM, respectively . Additionally, this compound was able to bind to cell-free viruses and to neutralize their infectivity in a plaque reduction assay .
[1] U. Grienke, M. Schmidtke, S. von Grafenstein, J. Kirchmair, K. R. Liedl, J. M. Rollinger, Nat Prod Rep 2012, 29, 11-36.
[2] P. Dresch, D. A. MN, K. Rosam, U. Grienke, J. M. Rollinger, U. Peintner, AMB Express 2015, 5, 4.
[3] U. Grienke, C. E. Mair, J. Kirchmair, M. Schmidtke, J. M. Rollinger, Planta Med 2018. doi 10.1055/a-0590-5153