title: Indirect photochemical transformations of acyclovir and penciclovir in aquatic environments increase ecological risk.
abstract: Acyclovir and penciclovir, 2 antiviral drugs, are increasingly detected in aquatic environments. The present study explores the natural photochemical transformation mechanisms and fate of these drugs, examining direct and indirect photochemical transformation under simulated sunlight irradiation. The 2 antiviral drugs are photostable under certain conditions but significantly degrade in the presence of chromophoric dissolved organic matter (DOM). The degradation rate associated with the drugs' indirect photochemical transformation scaled with chromophoric DOM concentration. Quenchers and sensitizers were used to identify indirect photochemical transformation mechanism. Results suggested that both pharmaceuticals could be transformed by reacting with (1)O2, (•)OH, and excited chromophoric DOM. The (1)O2 played an important role in indirect photochemical transformation. Furthermore, the reaction kinetics between their substructural molecules, guanine, isocytosine, and imidazole, with different reactive oxygen species were evaluated to determine which substrate functionalities were most susceptible to singlet oxygenation. Imidazole was identified as the reaction site for (1)O2, and preliminary (1)O2 oxidation mechanisms were further evaluated based on liquid chromatographic-tandem mass spectrometric results. Finally, aquatic ecotoxicity assessment of phototransformed solutions revealed that the degradation of acyclovir and penciclovir may not ultimately diminish environmental risk because of either formation of more toxic intermediates than parent pharmaceuticals or some synergistic effects existing between the intermediates.
authors.affiliation: State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, People's Republic of China.|University of Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: Jibin
authors.initials: J
authors.lastname: An
authors.affiliation: State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, People's Republic of China.
authors.forename: Guiying
authors.initials: G
authors.lastname: Li
authors.affiliation: State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, People's Republic of China.
authors.forename: Taicheng
authors.initials: T
authors.lastname: An
authors.affiliation: Institute of Hydrobiology, Jinan University, Guangzhou, People's Republic of China.
authors.forename: Xiangping
authors.initials: X
authors.lastname: Nie
mesh_terms: D000212:Acyclovir / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000633:toxicity; D000818:Animals; D000998:Antiviral Agents / Q000737:chemistry* / Q000633:toxicity; D002851:Chromatography, High Pressure Liquid; D003621:Daphnia / Q000187:drug effects / Q000502:physiology; D006147:Guanine; D007700:Kinetics; D058086:Microalgae / Q000187:drug effects / Q000502:physiology; D010084:Oxidation-Reduction; D010776:Photobacterium / Q000187:drug effects; D018570:Risk Assessment; D026082:Singlet Oxygen / Q000737:chemistry; D013472:Sunlight; D053719:Tandem Mass Spectrometry
chemical_list: D000998:Antiviral Agents; D026082:Singlet Oxygen; C053539:penciclovir; D006147:Guanine; D000212:Acyclovir
keywords: Antiviral drug; Ecological risk assessment; Photochemical transformation mechanism; Radical reaction; Singlet oxygen