A New Diketopiperazine from Trichothecium Crotocinigenum

A culture of Trichothecium crotocinigenum (syn. Acremonium crotocinigenum; MYC-2235 = NRRL 62714) was isolated from the black stromata of a pyrenomycete collected from a dead hardwood branch in Kipuka ki (Volcanoes National Park), Ka'u District, Hawaii. The culture was identified based on its micromorphology. Its ethyl acetate-soluble fermentation extract showed antifungal activity against Fusarium verticillioides and Aspergillus flavus as well as antiinsectan activity against Spodoptera frugiperda (fall armyworm) and was therefore chemically investigated. A new diketopiperazine was isolated and identified based on NMR and HRESIMS analysis. The new metabolite incorporates the uncommon amino acid 1-aminocyclopropane-1-carboxylic acid together with a pipecolic acid unit to form a new tricyclic ring system. Marfey's method was used to assign the absolute configuration. The known compounds 3-deoxotrichothecin and guangomide A (= hilodepsipeptide D) were also isolated from the extract and identified based on comparison of NMR data with literature values. The new metabolite exhibited mild antiinsectan activity, but 3-deoxotrichothecin was judged to be the major contributor to the activity originally exhibited by the extract.