Mass spectrometry of compounds of biological interest

Abstract

Mass spectrometric methods, including EI, CI, FAB and ESI LC/MS have been surveyed as tools for identification and characterization of compounds of natural origin exhibiting biological activity. Bioactive catechins isolated from green tea were analyzed by mass spectral methods: EI spectra provided both molecular weight and structural information, including epimer differentiation. FAB mass spectrometry gave both molecular weight and structural information on all compounds. ESI LC/MS provided unambiguous MW information on all compounds and some additional structural data on compounds ECG and EGCG. ESI LC/MS provided a means for separation of all compounds in a mixture and is an appropriate method for analysis of a crude extract of this plant material. Based on the result from biological testing, showing that quinic acid derivatives possess considerable anti-HIV activity, four analogs of dicaffeoylquinic acid were characterized by mass spectral methods. An attempt was made to design a mass spectral method allowing the differentiation between the analogs. FAB mass spectral analysis provided good MW information for all compounds. In addition, ions representing the elimination of water from MH+ ion of the 3,5-DCQA-OAc clearly differentiated this isomer from the 3,4-DCQA-OAc. MIKES analysis of the MH+ ions of the acetate derivative confirmed the isomer specific water loss. ESI provided unambiguous MW information on all compounds, confirming that loss of water is specific for the 3,5-DCQA-OAc. The extract of the CSF in patients with ALL was surveyed for a suitable biomarker which would indicate brain tissue damage following therapy. Phospholipid levels in CSF in three groups of patients receiving different CNS propylaxis were monitored during the course of treatment and the elevated levels were correlated to the cognitive impairment evaluation results. As a result of the CNS propylaxis, the levels of phospholipids in CSF are significantly elevated, indicating disruption of brain cell membranes. Two major classes of phospholipid were identified by FAB mass spectral analysis, PC and SM. Their elevated levels were inversely correlated with the decreased scores from cognitive testing. A close correlation was found between the PC levels and some test scores.