Analytical strategy for determination of known and unknown destruxins using hybrid quadrupole-Orbitrap high-resolution mass spectrometry.

An analytical strategy based on a hybrid quadrupole-Orbitrap mass spectrometry was proposed for the simultaneous screening of known destruxins and characterization of potential members of this class of secondary metabolites, in order to evaluate the metabolite production of entomopathogenic fungi used as biocontrol agents. Initially, the fragmentation pathway of the known and commercially available destruxin A was established combining high resolution mass spectrometry (HRMS) and multiple stage MS data in order to obtain the strategy for the characterization of other destruxins for which reference standards were not available. Nineteen known destruxins including A, B, C, D, Ed, F, A, B, Ed, A, B, D, A, DesmA, DesmB, DesmC, DesmB, and two chloro-derivatives (Cl and E chlorohydrin) were unequivocally identified in Metarhizium brunneum using the proposed strategy. In addition, four unknown destruxins, namely C, Ed, G, and G, were structurally elucidated and characterized for the first time in this fungal strain.