title: Sunlight-induced degradation of soil-adsorbed veterinary antimicrobials Marbofloxacin and Enrofloxacin.
abstract: Marbofloxacin (MAR) and Enrofloxacin (ENR), two largely employed veterinary Fluoroquinolones (FQs), were found to be present at the micrograms per kilogram level in agricultural soils of South Lombardy (Italy) several months after manuring. Distribution coefficients (K(d)) from sorption experiments indicated a strong binding to the soil. Soil samples fortified with environmentally significant FQs amounts (0.5 mg kg(-1)) were exposed to solar light that promoted extensive degradation (80%) of both drugs in 60-150 h. Thus, photochemistry could be considered a significant depollution path in the soil, although it was two orders of magnitudes slower than in aqueous solution and a fraction of the drug (ca. 20%) remained unaffected. For MAR the photoprocess was the same as in solution, and involved cleavage of the tetrahydrooxadiazine ring. On the contrary, with ENR only some of the photoproducts determined in water (those arising from a stepwise oxidation of the piperazine side chain) were observed. Substitution of the 6-fluoro by a hydroxyl group and reduction did not occur in the soil, supporting the previous contention that such processes required polar solvation of FQs. Consistently with this rationalization, the irradiation of thin layers of solid drugs led to essentially the same products distribution as in the soil. From the environmental point of view it is important to notice that photodegradation mainly affects the side-chains, while the fluoroquinolone ring, to which the biological effect is associated, is conserved up to the later stages of the degradation.
authors: Department of Chemistry, via Taramelli 12, 27100 Pavia, Italy. michela.sturini@unipv.it
authors: Michela
authors: M
authors: Sturini
authors: Andrea
authors: A
authors: Speltini
authors: Federica
authors: F
authors: Maraschi
authors: Antonella
authors: A
authors: Profumo
authors: Luca
authors: L
authors: Pretali
authors: Elisa
authors: E
authors: Fasani
authors: Angelo
authors: A
authors: Albini
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D000077422:Enrofloxacin; D052918:Environmental Restoration and Remediation; D024841:Fluoroquinolones / Q000032:analysis / Q000737:chemistry*; D010782:Photolysis; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013472:Sunlight
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D012989:Soil Pollutants; D000077422:Enrofloxacin; C080260:marbofloxacin