New secondary metabolites from bioactive extracts of the fungus Armillaria tabescens

Abstract

Ethyl acetate extracts of Armillaria tabescens (strain JNB-OZ344) showed significant fungistatic and bacteristatic activities against several major human pathogens including Candida albicans, Cryptococcus neoformans, Escherichia coli and Mycobacterium intracellulare. Chemical analysis of these extracts led to the isolation and identification of four new compounds, emestrin-F (1), emestrin-G (2), 6-O-(4-O-methyl-β-D-glucopyranosyl)-8-hydroxy-2,7-dimethyl-4H-benzopyran-4-one (3) and cephalosporolide-J (4), along with five other previously known compounds, emestrin (5), cephalosporolide-E (6), decarestrictine-C₂ (7), ergosterol and brassicasterol. Structural elucidation of all compounds was carried out by NMR and MS analyses. Antimicrobial assays revealed that compounds 1 and 5 were responsible for the observed growth inhibitory activities of the fungal extracts against the human pathogens tested.

Keywords:

• Armillaria tabescens
• emestrin
• chromone
• cephalosporolide
• antimicrobial activity

Acknowledgements

The authors thank Ms Marsha Wright for the biological testing. This study was supported by the NIH, NIAID, Division of AIDS, grant no. AI 27094 and the USDA Agricultural Research Service Specific Cooperative Agreement no. 58-6408-1-603.