¹Department of Pharmacognosy, Interdisciplinary Excellence Centre, University of Szeged, H-6720 Szeged, Hungary
²Spectroscopic Research Department, Gedeon Richter Plc., Gyömrői út 19-21, H-1103 Budapest, Hungary
³Department of Botany, Szent István University, H-1118 Budapest, Villányi út 29-43, Hungary
⁴Interdisciplinary Centre of Natural Products, University of Szeged, H-6720 Szeged, Hungary
⁵Department of Clinical Microbiology, University of Szeged, H-6720 Szeged, Hungary
⁶Department of Pharmacognosy, Semmelweis University, H-1085 Budapest, Hungary DOI : 10.35333/jrp.2020.250 In the course of our mycochemical studies the extract of Clitocybe nebularis was investigated with the aim to identify its bioactive secondary metabolites. Multistep chromatographic purification of the MeOH extract of C. nebularis resulted in the isolation of two steroids and an organic acid from the CHCl3 and ethyl acetate soluble fractions. The structures of the compounds were determined by NMR and MS spectroscopy as 5α-ergosta-7,22-diene-3β,5,6β-triol (cerevisterol) (1), (22E,24S)-5α-ergosta-7,22-diene-3β,5,6β,9α-tetraol (2), and indole-3-carboxylic acid (3). The antimicrobial activity of the compounds was analyzed by agar disc diffusion method against human pathogen strains of Streptococcus agalactiae, Staphylococcus epidermidis, Moraxella catarrhalis, Haemophilus influenzae, and Proteus mirabilis. The susceptibility assay revealed that compounds 2 and 3 have weak antimicrobial activity against M. catarrhalis. The current study represents the first isolation of compounds 1–3 from C. nebularis. Keywords : Clitocybe nebularis; steroids; antimicrobial activity; Tricholomataceae