Mass spectroscopy of natural products. III--Mass spectrometric comparison of lysergic acid and 9,10-dihydrolysergic acid

Mass spectrometry as an aid to the identification of ergots and dihydroergots: comparison of hard and soft ionization techniques

An analysis of the 70 eV electron impact (EI) and fast atom bombardment (FAB) mass spectral features of a variety of ergoline and dihydroergoline derivatives of therapeutic importance is presented with emphasis upon analytical utility. Derivatives which carry non-peptide based C-8 substituents are fully characterized by EI-MS through provision of molecular wieght evidence and fragment ions diagnostic of both the ergoline skeleton and the C-8 substituent. Peptidic ergolines and dihydroergolines are poorly characterized by EI-MS, but their FAB-MS clearly reveal [M + 1]+ (high intensity) and [M - 1]- (high to low intensity) ions in positive and negative ion spectra, respectively. Negative FAB spectra of salts also display diagnostic anion-base conjugate ions.