Cyclopeptides from Amanita exitialis

A new cyclic nonapeptide, amanexitide (1), along with the known cyclopeptides, a- and b-amanitins, was isolated from the fruiting bodies of Amanita exitialis, a newly described poisonous mushroom endemic to Guangzhou, Guangdong Province, China. Its amino acid composition and absolute configuration were determined by chemical degradation and derivatization followed by chiral GC analysis. Its amino acid sequence was elucidated by extensive analysis of ESIMS/MS and FTICRMS data. The occurrence of 1 in this mushroom is interesting because it has a structure closely related to antamanide, a cyclic decapeptide with antidote activity against amatoxins and phallotoxins, occurring in A. phalloides.