Keywords
1. UV degradation of pharmaceuticals
2. Chloramphenicol photolysis
3. PPCP environmental impact
4. Laser flash photolysis
5. Quantum yields in photodegradation
The understanding of how pharmaceutical drugs degrade in the environment has taken a significant step forward thanks to a new study published in Chemosphere by a team of Russian scientists. Researchers at various institutions, including the Voevodsky Institute of Chemical Kinetics and Combustion (SB RAS) and Novosibirsk State University, have illuminated the mechanism of ultraviolet (UV) photolysis of the antibiotic chloramphenicol (CAP). The groundbreaking research, detailed in “Laser flash photolysis and quantum chemical studies of UV degradation of pharmaceutical drug chloramphenicol: Short-lived intermediates, quantum yields and mechanism of photolysis,” has identified short-lived intermediates that play a crucial role in the degradation process, findings that have far-reaching implications for both environmental and public health.
Chloramphenicol is a broad-spectrum antibiotic that has been used to treat a variety of bacterial infections. However, its presence in the environment, particularly in natural and wastewater systems, has been a cause for concern due to its persistence and potential to contribute to antibiotic resistance. The study’s lead authors, Yury A. Belikov and Ivan P. Pozdnyakov, alongside their colleagues Olga A. Snytnikova, Dmitriy G. Sheven, Roman G. Fedunov, and Vyacheslav P. Grivin, have employed sophisticated laser flash photolysis and quantum-chemical calculations using the Density Functional Theory (DFT) method to expose the behavior of CAP under UV radiation.
The primary photolysis process involves the cleavage of the β-C-C bond adjacent to the aromatic system. This results in the formation of a 4-nitrobenzylalcohol radical and a residual aliphatic radical. These radicals, never before detected due to their transient nature, are significant as they indicate a potential pathway for the degradation of CAP in the presence of UV light, which is abundant in natural sunlight.
In deoxygenated solutions, the 4-nitrobenzylalcohol radical primarily transforms into para-nitrobenzaldehyde, which subsequently undergoes secondary photolysis. Conversely, in the presence of oxygen, both the aromatic radical and para-nitrobenzaldehyde are converted into para-nitrosobenzoic and para-nitrobenzoic acids. This transformation is induced by reactive oxygen species (ROS), which are produced through the reaction of the aliphatic radical with dissolved oxygen. The behavior of the aliphatic radical is a critical factor for the degradation of CAP, as its interaction with oxygen not only forms compounds that are more manageable by environmental processes but also minimizes the generation of potentially harmful side products.
The quantum yield of direct photolysis for CAP, estimated to be approximately 3%, was found to be independent of both dissolved oxygen and variations in the excitation wavelength range from 254 to 308 nm. This relatively low quantum yield underlines the efficiency of CAP’s photolysis and the consequent potential to significantly reduce the concentration of this antibiotic in the environment when exposed to UV light.
The impact of pharmaceutical and personal care products (PPCPs) on the environment has increasingly drawn the attention of scientists and policy-makers. As components of PPCPs persist in water bodies, their continuous input and accumulation can pose risks to both ecosystems and human health. The findings reported in this study contribute valuable knowledge, suggesting that direct photolysis, stimulated by sunlight or artificial UV radiation, could be an effective way to mitigate such risks, at least for CAP and possibly for similar PPCPs.
Moreover, these findings have practical implications for wastewater treatment. Current methods may not fully remove PPCP contaminants, and understanding the precise mechanisms of their degradation in the presence of UV light can inform the development of more efficient treatment technologies. By using UV radiation in treatment processes with informed knowledge about quantum yields and reactive intermediates, it might be possible to enhance the breakdown of these persistent compounds.
To gain a comprehensive understanding of the UV degradation of CAP, the team employed high-performance liquid chromatography-mass spectrometry (HPLC-MS), enabling the detection of transformation products. The identification of specific intermediates and end-products of the photolysis process provides insights into the potential toxicity and bioaccumulative properties of the degradation compounds, which in turn affect the assessments of environmental impacts and develop regulatory policies.
The novelty of this research is undoubted. The scientists’ ability to detect, for the first time, short-lived intermediates associated with CAP photolysis paves the way for deeper investigations into the environmental fate of similar compounds. The collaboration between chemists and environmental scientists underlines the interdisciplinary nature of the research, a synthesis that is increasingly recognized as essential to tackling complex environmental challenges.
The authors of the study, while having meticulously disclosed their findings, also assert that they have no known competing financial interests or personal relationships that could have appeared to influence the reported work, ensuring the integrity and objectivity of the research.
This study is an insightful addition to the existing body of knowledge concerning environmental photodegradation of pharmaceuticals. The collaboration across Russian institutions emphasizes the global nature of environmental science and the importance of international cooperation in confronting environmental concerns.
The research, published with the DOI: 10.1016/j.chemosphere.2024.141211, provides both an academic and practical framework for future initiatives focusing on the safeguarding of water quality and the overall health of ecosystems from the effects of PPCPs.
References
1. Belikov, Y. A., et al. (2024). Laser flash photolysis and quantum chemical studies of UV degradation of pharmaceutical drug chloramphenicol: Short-lived intermediates, quantum yields and mechanism of photolysis. Chemosphere, 351(2024), 141211. doi:10.1016/j.chemosphere.2024.141211
2. Chemosphere Journal. (n.d.). Retrieved from https://www.journals.elsevier.com/chemosphere
3. Lai, W. W. P., et al. (2012). Removal of antibiotics from wastewater by sewage treatment facilities in Hong Kong and Shenzhen, China. Water Research, 46(2), 395-403.
4. Xie, Y., et al. (2016). Photodegradation and toxicity changes of antibiotics in UV and UV/H2O2 process. Journal of Hazardous Materials, 319, 48-55.
5. Serna-Galvis, E. A., et al. (2016). Super-high frequency ultrasound as a potential and cost-effective technique for improving antibiotics degradation assisted by advanced oxidative processes: Kinetic and transformation products. Science of The Total Environment, 565, 1119-1126.
By translating this complex scientific research into digestible insights, this article empowers both specialists and the general public with an understanding of the importance of managing pharmaceutical pollution. Environmental scientists, water treatment professionals, and policy-makers can harness the knowledge of these breakthroughs to foster healthier ecosystems and a cleaner water supply.