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Characterization of moenomycin antibiotics from medicated chicken feed by ion‐trap mass spectrometry with electrospray ionization
Author(s) -
Eichhorn Peter,
Aga Diana S.
Publication year - 2005
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2044
Subject(s) - chemistry , adduct , electrospray ionization , protonation , mass spectrometry , fragmentation (computing) , mass spectrum , chromatography , ion , stereochemistry , organic chemistry , computer science , operating system
The antimicrobial moenomycin, commonly used as a growth promoter in livestock, was isolated from medicated chicken feed. The purified extract was subjected to reversed‐phase liquid chromatographic separation followed by structural characterization using ion‐trap mass spectrometry (ITMS), which allowed identification of five moenomycins (A, A 12 , C 1 , C 3 , and C 4 ) as the major components. The fragmentation patterns of the protonated and deprotonated moenomycin molecules, as well as of a series of sodium adducts, were investigated using ITMS after electrospray ionization. While the protonated molecules [M+H] + proved highly unstable and underwent extensive in‐source fragmentation, isolation and activation of the [MH] − ions ( m/z 1580 for moenomycin‐A) yielded simple mass spectra with a dominant base peak corresponding to the loss of the carboxy‐glycol and the C 25 ‐hydrocarbon chain ( m/z 1152 for moenomycin‐A). Further study of this fragment ion in an MS 3 experiment gave rise to a peculiar product ion ( m/z 902 for moenomycin‐A) that was attributed to the expulsion of a carbohydrate moiety representing a central building block of the linear molecule. In positive ion mode the generation of the mono‐sodiated adduct ions, [M+Na] + , was promoted by amending the mobile phase with 100 µM sodium acetate, but this also resulted in higher adducts of the type [M+2NaH] + and [M+3Na2H] + arising from the formation of the sodium salts of the phosphate acid diester and subsequently of the carboxylic acid. Substantial differences among the fragment‐rich product ion profiles of the three species were observed, and could in part be traced back to the mode of complexation of the additional sodium cation(s). Copyright © 2005 John Wiley & Sons, Ltd.