Benzoxepine Esters as Precursors of the Wound‐Activated Chemical Defence of Mycena galopus

Abstract

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)

Chemical Defence Strategies of Higher Fungi

“…In contrast to the bioactivity-guided comparative screening, the second method for the elucidation of wound-activated chemical defence mechanisms, namely comparative metabolic screening, is based on a comparison of the metabolite pattern of extracts from intact and injured fruiting bodies. [57] Secondary metabolites which are only present in significant amounts in injured fruiting bodies are potential candidates for defence compounds, while secondary metabolites which are only present in intact fruiting bodies might be their potential precursors. In contrast to the comparative biological screening of crude extracts, the comparative metabolic screening allows often recognition of the relationship between precursor and the corresponding defence compound, especially if the metabolic screening is performed by LC-UV, LC-ESIMS or GC-EIMS, since the precursor and the www.chemeurj.org corresponding active metabolite usually share structural elements which are reflected in similar UV spectra, MS/MS spectra or fragmentation patterns in the GC-EIMS.…”

“…Interestingly, the benzoxepine esters and the esterase responsible for their saponification are evidently stored in separate compartments in the intact fruiting bodies, since the benzoxepine esters in the latex were only hydrolysed if the latex was mixed with homogenised fungal tissue. [57] In contrast to the wound-activated defence mechanisms discussed so far, the bioactive compound in Paxillus atrotomentosus is derived from the acid moiety. [69] Upon injury of the fruiting-bodies the inactive leucomentins such as leucomentin-3 (43) are hydrolysed and subsequently converted to atromentin (44), (+)-osmundalactone (45) and butenolide 46 (Scheme 6).…”

“…In contrast to the bioactivity‐guided comparative screening, the second method for the elucidation of wound‐activated chemical defence mechanisms, namely comparative metabolic screening, is based on a comparison of the metabolite pattern of extracts from intact and injured fruiting bodies 57. Secondary metabolites which are only present in significant amounts in injured fruiting bodies are potential candidates for defence compounds, while secondary metabolites which are only present in intact fruiting bodies might be their potential precursors.…”

Receives Prize Electrochemistry: A. Heller Honored / Awarded Nanomaterials: M. A. El‐Sayed / Organic Chemistry: L. Gooßen, R. Sarpong, O. Trapp, J.‐Q. Yu, and A. Zakarian / Biotechnology: C. M. Niemeyer / Honored Chemical Ecology: Prize to P. Spiteller

“…In the European Journal of Organic Chemistry he reported last year on benzoxepine esters as precursors of the wound-activated chemical defence of Mycena galopus. [9] O. Trapp Receives Innovation Prize Oliver Trapp was awarded the E 50 000 Innovation Prize of the State of North Rhine-Westfalia in the "young researcher" category. He is thus recognized for the outstanding achievements in catalysis that he has already made early in his scientific career.…”

Elektrochemie: A. Heller geehrt / Nanomaterialien: M. A. El‐Sayed erhält Preis / Organische Chemie: L. Gooßen, R. Sarpong, O. Trapp, J.‐Q. Yu und A. Zakarian ausgezeichnet / Biotechnologie: C. M. Niemeyer geehrt / Chemische Ökologie: Preis für P. Spiteller

“…Im European Journal of Organic Chemistry berichtete er letztes Jahr über Benzoxepinester als Vorstufen der wundaktivierten chemischen Verteidigung von Mycena galopus. [9] O. Trapp [10] und für die Angewandte Chemie verfasste er ein Highlight über molekulare Sensoren.…”