Title

Environmental photochemistry of tylosin: efficient, reversible photoisomerization to a less-active isomer, followed by photolysis

Department/School

Chemistry

Date

8-22-2007

Document Type

Article

Keywords

Tylosin; environmental fate; photolysis; quantum yield; antibiotic activity

DOI

https://doi.org/10.1021/jf070101h

Abstract

The environmental photochemical kinetics of tylosin, a common veterinary macrolide antibiotic and growth promoter, were investigated under simulated sunlight. An efficient, reversible photoisomerization was characterized using kinetic, mass spectrometry, and proton nuclear magnetic resonance data. The photoisomerization was confirmed to occur by a rotation about the distal alkene of the ketodiene functionality. Concurrent forward (quantum yield = 0.39 ± 0.09) and back (quantum yield = 0.32 ± 0.08) reactions lead to a photochemical equilibrium near a tylosin/photoisomer ratio of 50:50, completed in less than 2 min under a spectrum equivalent to noontime, summer sunlight. The activity of the isomer for the inhibition of Escherichia coli DH5α growth was observed to be less than that of tylosin. On a longer time scale than that of isomerization, the isomer mixture undergoes photolysis with a quantum yield of (1.4 ± 0.3) × 10-3. The observed quantum yields and UV−vis absorbance data allow for the prediction of the photochemical behavior of tylosin in most environmental systems. Indirect photosensitization was not a significant loss process in solutions of Suwannee River fulvic acid with concentrations from 1 to 20 mg L-1.

Published in

Journal of Agricultural and Food Chemistry

Citation/Other Information

Werner, J.J., M. Chintapalli, R.A. Lundeen*, K.H. Wammer, W.A. Arnold, K. McNeill. 2007. “Environmental photochemistry of tylosin: efficient, reversible photoisomerization to a less-active isomer, followed by photolysis.” Journal of Agricultural and Food Chemistry. 55(17):7062-7068. DOI: 10.1021/jf070101h

This document is currently not available here.

Share

COinS