TANDEM MASS SPECTROMETRIC ANALYSES OF MATERIALS OF NATURAL ORIGIN AND WITH MEDICINAL PROPERTIES
Abstract
Materials of natural origin were chosen to further explore the analytical utility of tandem mass spectrometry. Direct analysis of plant materials led to the discovery of new natural products. Numerous new alkaloids were discovered in the species Pachycereus weberi and Cephalotaxus harringtonia. This method of analysis revealed the alkaloid distribution in Cephalotaxus harringtonia. The analysis of Psorospermum febrifugum suggested the presence of two chlorine-containing isomeric xanthones and Artemisia annua revealed an additional natural product. The structures of the new natural products are postulated based on interpretation of the fragmentation patterns and recognition of key fragment ions. In many cases structural assignments are confirmed by other techniques. Structural characterization of natural products is achieved for this first time through ion/molecule reactions. Minor structural differences are shown to cause significant reactivity changes for the reactions of the protonated molecules with ethyl vinyl ether. The products occur at high relative abundances, often greater than that of the reacting ion. Studies of the reactivity of protonated model compounds and neutral polar organic compounds has allowed functional group identification and isomer differentiation. The mechanisms of the model compound studies are interpreted and can be applied to natural product studies. The tandem mass spectrometric analysis of the products of potassium/crown ether reduction of a bituminous coal indicates that alkyl naphthalene structures are an integral part of the original coal. Alkyl dihydronaphthalene and alkyl tetralin compounds, which are also detected, are the reduction products of the alkyl naphthalenes. The products of this gentle reaction are suggested to be part of the macromolecular network of the coal. A compilation of collisionally-activated dissociation data of acridine derivatives reveals characteristic fragmentations. These data are important for identification of these biologically-active compounds in complex mixtures and in regard to gas phase dissociation chemistry. The fragmentations of the protonated molecules and radical molecular ions are interpreted.
Degree
Ph.D.
Subject Area
Analytical chemistry
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.