SHORT COMMUNICATION

 

Synthesis and antimicrobial activity of the essential oil compounds (E)- and (Z)-3-hexenyl nonanoate and two analogues

 

 

Santanu Chakravorty^I; Matthew K. Rayner^I; Charles B. de Koning^I; Sandy F. van Vuuren^{II, *}; Willem A.L. van Otterlo^{I, III, *}

^IMolecular Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Wits, 2050, South Africa
^IIDepartment of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa
^IIIDepartment of Chemistry and Polymer Sciences, Stellenbosch University, Stellenbosch, 7600, Western Cape, South Africa

 

 

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ABSTRACT

The synthesis of (E)- and (Z)-3-hexenyl nonanoate, known constituents of essential oil containing plants, and two related compounds is reported. These compounds were assembled from nonanoyl chloride or nonanoic acid and the respective alcohols. In particular, it was found that the use of triethylamine as a co-solvent was necessary to avoid acid-mediated isomerization of the alkenes, which resulted in an inseparable mixture of products. The antimicrobial activity of the four hexenyl and hexyl nonanoate compounds was undertaken using microdilution minimum inhibitory concentration (MIC) analysis against eight test microorganisms. All four compounds demonstrated activity, with (E)-3-hexenyl nonanoate 1B: having the highest inhibition (MIC value of 0.45 mg mL^-1) against Pseudomonas aeruginosa ATCC 27858. Furthermore, this compound demonstrated the highest broad-spectrum activity (mean MIC value of 1.24 ± 0.50 mg mL^-1) with noteworthy activity against all pathogens tested.

Keywords: Essential oil constituent, (E)- and (Z)-3-hexenyl nonanoate, antimicrobial, ester synthesis, acid-induced alkene isomerizations

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Acknowledgements

This work was supported by the National Research Foundation (NRF), Pretoria, The University of the Witwatersrand (University and Science Faculty Research Councils) and Stellenbosch University (Faculty and Departmental funding). Thanks go to the NRF for a postdoctoral Innovations Fellowship. We also gratefully acknowledge Mr. R. Mampa for the NMR spectroscopy service. Finally, Mr. B. Moolman, Mr. F. Hiten and Dr. M. Stander (Stellenbosch University) are acknowledged for providing MS spectroscopy services.

 

References and Notes

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21 J.N. Eloff, Planta Med., 1998, 64, 711-713.         [ Links ]

 

 

Received 9 August 2012
Revised 26 August 2012
Accepted 2 September 2012

 

 

* To whom correspondence should be addressed. E-mail: sandy.vanvuuren@wits.ac.za / wvo@sun.ac.za