Benzoxepine Esters as Precursors of the Wound-Activated Chemical Defence ofMycena galopus

The native precursors E/Z-1a to E/Z-1e and 2a–2e of the antifungally active benzoxepines E/Z-1 and 2 have been isolated from intact fruiting bodies of Mycena galopus. These precursors turned out to be fatty acid esters of the benzoxepines (pterulones) E/Z-1 and 2. Metabolic profiling of ethyl acetate extracts from intact fruiting bodies, from the latex and from mechanically wounded fruiting bodies revealed that the known antifungally active benzoxepines E/Z-1 and the previously unknown benzoxepines 2 are only present in injured fruiting bodies. Intact fruiting bodies and the latex, however, exclusively contain the corresponding ester derivatives E/Z-1a to E/Z-1e and 2a–2e. Unlike the antifungally active benzoxepines E/Z-1 and 2, the esters E/Z-1a to E/Z-1e present in intact fruiting bodies turned out to be inactive. Upon injury the inactive esters E/Z-1a to E/Z-1e are cleaved by a putative esterase, and the bioactive benzoxepines E/Z-1 and 2 are released, suggesting a wound-activated defence mechanism of M. galopus against yeasts and parasitic fungi. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)