title: Kinetic and mechanistic aspects of sensitized photodegradation of β-lactam antibiotics: microbiological implications.
abstract: Amoxicillin (Amx) and cephalexin (Cfx) are β-lactam antibiotics widely used in human and veterinary medicine. Two points of interest surrounding these molecules are the photodegradation of the molecules and their microbiological implications, as well as the persistence and bioaccumulation  in the environment which may cause resistance to bacterial strains. The kinetic and mechanistic aspects of the photosensitized degradation of Amx and Cfx have been studied in water at pH 7.4 and 10 by stationary and time-resolved methods. Kinetic evidence indicates that the Rose Bengal-sensitized  photooxidation of Amx at pH 7.4 proceeds via O(2)((1)Δ(g)) and O(2•-) mechanisms while at pH 10 the degradation path occurs, principally, via O(2)((1)Δ(g)).  For Cfx, this process is attributed to O(2)((1)Δ(g)) and O(2•-). Photoproducts, which arise from the addition of oxygen atoms and subsequent oxidation of the groups -CH(3)  to -COOH, were detected. For both antibiotics the bacteriostatic activity decreases in parallel to their photodegradation. The results of this study could potentially help scientists to better understand and predict the photodegradability of these antibiotics on living organisms and  in different environmental compartments.
authors: Departamento de Química, Universidad Nacional de Río Cuarto, Rio Cuarto, Argentina.
authors: E
authors: E
authors: Reynoso
authors: A
authors: A
authors: Nesci
authors: P
authors: P
authors: Allegretti
authors: S
authors: S
authors: Criado
authors: M A
authors: MA
authors: Biasutti
mesh_terms: D000658:Amoxicillin / Q000737:chemistry / Q000494:pharmacology / Q000528:radiation effects*; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology / Q000528:radiation effects*; D002506:Cephalexin / Q000737:chemistry / Q000494:pharmacology / Q000528:radiation effects*; D002851:Chromatography, High Pressure Liquid; D004350:Drug Residues; D004783:Environmental Microbiology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D010084:Oxidation-Reduction; D043803:Phenalenes / Q000494:pharmacology; D010782:Photolysis; D017319:Photosensitizing Agents / Q000494:pharmacology; D012395:Rose Bengal / Q000494:pharmacology; D026082:Singlet Oxygen / Q000737:chemistry; D012996:Solutions; D013053:Spectrophotometry; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D013481:Superoxides / Q000737:chemistry; D014867:Water
chemical_list: D000900:Anti-Bacterial Agents; D043803:Phenalenes; D017319:Photosensitizing Agents; D012996:Solutions; D014867:Water; D013481:Superoxides; D026082:Singlet Oxygen; D012395:Rose Bengal; C038036:phenalen-1-one; D000658:Amoxicillin; D002506:Cephalexin