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

Jeffrey J. Werner, Mahati Chintapalli, Rachel A. Lundeen, Kristine H. Wammer, William A. Arnold, Kristopher McNeill

Research output: Contribution to journalArticle

19 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)7062-7068
Number of pages7
JournalJournal of agricultural and food chemistry
Volume55
Issue number17
DOIs
StatePublished - Aug 22 2007

Keywords

  • Antibiotic activity
  • Environmental fate
  • Photolysis
  • Quantum yield
  • Tylosin

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