Mass spectrometry as a tool for the selective profiling of destruxins; their first identification in Lecanicillium longisporum.

Mass spectrometry was applied to the identification of the destruxins (dtxs), cyclic peptides that are commonly produced by the fungal insect-pathogen, Metarhizium anisopliae. The aim of the study was to optimise a methodology in order to firstly determine whether these compounds were present in other species and to determine the effect of differing growth conditions upon the dtx content detected. Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-ToF-MS) was initially used to analyse the dtxs, but limitations were indicated. Nano-scale high-performance liquid chromatography/electrospray ionisation mass spectrometry (HPLC/ESI-MS) and automated 'data-dependent' tandem mass spectrometric (MS/MS) analysis were also applied, utilising characteristic neutral losses during fragmentation to confirm the presence of the dtxs. This latter approach distinguished the dtx E and B isoforms by retention time and diagnostic neutral losses during fragmentation allowing extraction of the destruxin data from a complex dataset. This process revealed the presence of a number of dtxs in the fungal species Lecanicillium longisporum, a species previously not known to produce dtxs, and dtx production in this species was shown to be significantly higher in aerated cultures compared with still cultures. Copyright (c) 2009 John Wiley & Sons, Ltd.