title: Abiotic degradation of antibiotic ionophores.
abstract: Hydrolytic and photolytic degradation were investigated for the ionophore antibiotics lasalocid, monensin, salinomycin, and narasin. The hydrolysis study was carried out by dissolving the ionophores in solutions of pH 4, 7, and 9, followed by incubation at three temperatures of 6, 22, and 28 °C for maximum 34 days. Using LC-MS/MS for chemical analysis, lasalocid was not found to hydrolyse in any of the tested environments. Monensin, salinomycin, and narasin were all stable in neutral or alkaline solution but hydrolysed in the solution with a pH of 4. Half-lives at 25 °C were calculated to be 13, 0.6, and 0.7 days for monensin, salinomycin, and narasin, respectively. Absorbance spectra from each compound indicated that only lasalocid is degraded by photolysis (half-life below 1 h) due to an absorbance maximum around 303 nm, and monensin, salinomycin, and narasin are resistant to direct photolysis because they absorb light of environmentally irrelevant wavelengths.
authors.affiliation: Toxicology Laboratory, Analytical Biosciences, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: pb@e-mail.dk.
authors.forename: Pernille
authors.initials: P
authors.lastname: Bohn
authors.forename: Søren A
authors.initials: SA
authors.lastname: Bak
authors.forename: Erland
authors.initials: E
authors.lastname: Björklund
authors.forename: Kristine A
authors.initials: KA
authors.lastname: Krogh
authors.forename: Martin
authors.initials: M
authors.lastname: Hansen
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000737:chemistry*; D007832:Lasalocid / Q000737:chemistry; D008956:Models, Chemical; D008985:Monensin / Q000737:chemistry; D010782:Photolysis; D011714:Pyrans / Q000737:chemistry; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D000095662:Polyether Polyketides
chemical_list: D000900:Anti-Bacterial Agents; D007476:Ionophores; D007832:Lasalocid; D008985:Monensin; D011714:Pyrans; D014874:Water Pollutants, Chemical; C010327:salinomycin; D000095662:Polyether Polyketides; C013612:narasin
keywords: Degradation; Hydrolysis; Ionophore; LC–MS/MS; Photolysis