Determination and identification of the solanapyrones and new metabolites from Ascochyta rabiei

Abstract

A simple, rapid, accurate and robust liquid chromatography / mass spectrometry (LC/MS) method was developed for the determination and quantification of the solanapyrones and new metabolites. Portions of the crude solvent extracts of culture filtrate from Ascochyta rabiei, agent of chickpea blight were also analysed for confirmation by combined LC with time-of-flight (TOF)-MS. Isolate Haypa 3 of A. rabiei was grown on Czapek Dox liquid medium supplemented with the inorganic cations for 7, 14 and 21 days. After the culture filtrates were extracted by solid phase extraction using C18 cartridge, toxins were eluted with acetonitrile (ACN). In addition to the three solanapyrones, a new metabolite in the culture filtrates of A. rabiei was identified by LC / electrospray ionization (ESI)-MS and LC/TOF-MS. The new metabolite was determined in the culture filtrate on 21(st) day in vitro growth of the fungus. The new metabolite eluting at 8.33 min was found to have an accurate mass of m/z 319.1603. The elemental composition calculator produced a formula based on the ion at m/z 319.1603 which indicated the formula of C18H22O5.