Abstract
Untreated eggs of the tick Amblyomma hebraeum Koch (Acari: Ixodidae) exhibited antimicrobial activity (AMA) against Gram-negative but not Gram-positive bacteria; eggs denuded of wax by solvent extraction showed no AMA. The unfractionated egg wax extract, however, showed AMA against Gram-positive but not Gram-negative bacteria, as also shown by Arrieta et al. (Exp Appl Acarol 39: 297–313, 2006). In this study we partitioned the egg wax into various fractions, using a variety of techniques, analyzed their compositions, and tested them for AMA. The crude aqueous extract exhibited AMA. However, although more than 30 metabolites were identified in this extract by nuclear magnetic resonance analysis, none of them seemed likely to be responsible for the observed AMA. In the crude organic extract, cholesterol esters were the most abundant lipids, but were devoid of AMA. Fatty acids (FAs), with chain lengths between C13 and C26 were the next most abundant lipids. After lipid fractionation and gas chromatography/mass spectroscopy, free FAs, especially C16:1 and C18:2, accounted for most of the AMA in the organic extract. The material responsible for AMA in the crude aqueous extract remains unidentified. No AMA was detected in the intracellular contents of untreated eggs.
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Acknowledgments
The visit of Zhijun Yu to the University of Alberta was generously supported by China Scholarship Council and Hebei Normal University. We are grateful to (1) Mr. Audric Moses of the Lipid and Lipid Metabolite Analysis Core Facility, a service of the Women and Children’s Health Research Institute at the University of Alberta, for GC analysis of the organic extract, (2) to Mr. Ramanarayan Krishnamurthy and Ms. Rupasri Mandal of The Metabolomics Innovation Centre, U Alberta for the GC/MS and NMR analyses respectively of FAs, and (3) Mr. Troy Locke, Mr. Alexander Smith, Mr. Shahid Ullah, and Dr. Susan Jensen from the Department of Biological Sciences, for general advice and assistance throughout this study. This research was generously supported by a Discovery grant to WRK from the Natural Sciences and Engineering Research Council of Canada (NSERC). Dr. René Jacobs is a Canadian Institutes of Health Research New Investigator.
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Yu, Z., Thomson, E.L.S., Liu, J. et al. Antimicrobial activity in the egg wax of the tick Amblyomma hebraeum (Acari: Ixodidae) is associated with free fatty acids C16:1 and C18:2. Exp Appl Acarol 58, 453–470 (2012). https://doi.org/10.1007/s10493-012-9586-1
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DOI: https://doi.org/10.1007/s10493-012-9586-1