Pseudallescheria boydii is an emerging fungal human pathogen causing serious disease in both
immunocompromised and immunocompetent patients. Recent report showed that this fungus is capable of
controlling black leaf spot of cabbage caused by Alternaria brassicicola by producing a fungistatic substance
strongly inhibitory to fungi. Production of the inhibitory substance by P. boydii during colonization of plant
tissues in soil appears to account for its strong competitive saprophytic ability and widespread occurrence in soil. In this study, freeze-dried powder of liquid culture of P. boydii was extracted with ethanol and fractionated on silica gel column to give four fractions. The most active fraction was further purified by silica gel chromatography. The resulting compound 1 was structurally characterized as 6-6’-bis (2H-pyran-3-carbaldehyde) ether which is a new natural product showing strong inhibitory activity against A. brassicicola. The new antibiotic, a yellow oil with a molecular weight of 234, was named pseudallin. To our knowledge, this is the first report of antibiotic production by a non-dermatophyte human pathogenic fungus. Results from this study indicate the importance of antibiotic production in competitive saprophytic colonization of plant debris by P.boydii in soil, which in turn may explain its widespread occurrence.
