Mass Spectrometry of Algal Chlorophyll c Compounds

Abstract

Background: The term chlorophyll c encompasses a small but heterogeneous group of algal pigments, characterized for being porphyrins rather than chlorins. Chlorophylls c are protochlorophyllide-type compounds that differ in their peripheral substituents. Mass spectrometry has contributed to the structural elucidation of chlorophylls c, often in parallel with the development of soft ionization techniques

Objective: To provide comprehensive information on the structural characterization of chlorophylls c by mass spectrometry

Method: A detailed exam of the existing bibliography from both the chemical and marine science literatures followed by the analysis of data on molecular masses and product ions. Previous tandem mass spectra of chlorophyll c pigments are reproduced employing high resolution mass spectrometry.

Results: This article reviews the application of direct and tandem mass spectrometry techniques to the analysis of acidic and esterified chlorophylls c, summarizes their fragmentation patterns and enumerates some experimental fragmentation rules for their identification. The high resolution mass spectra of acidic and esterified chlorophyll c compounds are shown as characteristic examples.

Conclusion: The combined information on the molecular mass and diagnostic fragmentation allows the unambiguous characterization of the known acidic chlorophylls c, including the discrimination of isomeric pigments. Tandem mass spectrometry is a technique of choice for the study of galactolipid-esterified chlorophylls c, as the systematic fragmentation of successive parts in the molecules allows good tentative approaches to their structures.