A second steroidal constituent of the Alternaria genus, ergosterol peroxide, isolated from A , dianthicola, may be an artefact.Exhaustive extraction of the mycelium of Alternaria dianthicola revealed the presence of ergosterol peroxide.Although ergosterol peroxide has been isolated from a number of microorganism~,~-' this is the first report of the isolation of this compound from the genus Alternaria. The only other steroid isolated from this genus was a C , , steroid by Sugiyama et aL8 However, this steroid has not been completely characterized.Identification of ergosterol peroxide was accomplished by means of spectroscopic techniques and confirmed by comparison with an authentic sample. The infrared spectra of the natural product and the synthetic sample were superimposable.It is not known, however, whether ergosterol peroxide is the actual metabolite or whether it is produced from ergosterol by photooxidation during the workup procedure. Ergosterol has previously been isolated from f~n g i l ,~ and Adam et al.' have shown that some fungal extracts contain coloured materials which are able to act as photosensitizers for the oxidation of ergosterol to ergosterol peroxide.
ExperimentalMelting points were determined on a Kofler block and are uncorrected. The infrared, nuclear magnetic resonance and mass spectra were recorded on Perkin-Elmer 457, Jeol 100 and AEI MS 902 spectrometers respectively. The culture was obtained from the Department of Microbiology, University of Queensland. Kieselgel G (Woelm) was used for column chromatography.
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