Study of the simulated sunlight photolysis mechanism of ketoprofen: the role of superoxide anion radicals, transformation byproducts, and ecotoxicity assessment

Quantitative structure-activity relationship models for the reaction rate coefficients between dissolved organic matter and PPCPs

To predict PPCPs' photolysis rate in natural aquatic environment, it is essential to grasp the reaction rates between DOM and PPCPs, yet there are few measured data and no prediction models for this important photochemical parameter. To address this, a reaction rate coefficient (α_DOM) was defined to describe the apparent rate of DOM-involved photoreaction for PPCPs. The measured α_DOM values for 40 PPCPs in 9 DOM samples varied dramatically, ranging from (-2.1 ± 0.1)× 10¹⁰ to (2.2 ± 0.1)× 10¹¹ M^-1 s^-1. Then the quantitative structure-activity relationship (QSAR) models were developed using chemical and water quality descriptors via the random forest method. We initially separated positive and negative values by a classifier with an AUC value of 0.965, followed by the construction of regression models for positive and negative values, respectively, using a regressor. Positive models achieved satisfactory goodness-of-fit and predictive ability (R²_adj=0.92 and Q²_ext=0.86), while negative models demonstrated acceptable performance (R²_adj=0.71 and Q²_ext=0.70). Finally, a comprehensive photolysis model that incorporates the QSAR models for α_DOM was established and the significance of water quality parameters was emphasized through sensitive analysis. This model enables more elaborate predictions of PPCPs' photolysis rates in various water samples, providing valuable assistance for forecasting PPCPs' environmental fate.

Causes and countermeasure for blank absorbance increase in the ROS assay

A reactive oxygen species (ROS) assay is an in chemico photoreactivity test listed in ICH S10 guideline and OECD Test Guideline No. 495. We currently utilize the ROS assay to assess the photosafety of cosmetic ingredients. We have recently confronted a problem that there was an absorbance increase of blank assessing superoxide anion generation after irradiation, whereas this did not occur in the negative control (sulisobenzone), leading to a dissatisfaction of the acceptance criteria. Therefore, we aimed to investigate the causes and find countermeasures. No significant effects of impurities and manufacturer differences of sodium phosphate and DMSO on blank absorbance increases were observed. In contrast, when Cu²⁺ was added to the buffer, the increase of blank absorbance after irradiation did not occur. We then confirmed the dose-response relationship and found that adding 0.1 μM of Cu²⁺ (corresponding to 6 ppb of Cu²⁺) was sufficient in suppressing the blank absorbance increase, suggesting the need of Cu²⁺ supplementation to the buffer. Finally, we confirmed that the ROS assay using the buffer supplemented with 0.1 μM of Cu²⁺ obtained stable test results by using 17 proficiency chemicals listed in TG 495. Our results suggest that the modified ROS assay protocol would be useful for obtaining stable test results.

Aquatic photolysis of ketoprofen generates products with photosensitizing activity and toxicity

Ketoprofen (KTF) is a nonsteroidal anti-inflammatory drug frequently detected in natural and engineering waters. Because KTF is particularly photolabile (half-life ∼4 min), knowledge of the fate and ecological risks of KTF photoproducts in the aquatic environment is especially essential. Herein, we systematically investigated the photophysics, photochemistry, and photosensitization of KTF photoproducts in aqueous solution under 365 nm irradiation (UV₃₆₅). Results show that KTF photolyzed rapidly and formed 3-ethyl-α-hydroxylbenzophenone (EtOH-BP), 3-ethyl-α-hydroperoxylbenzophenone (EtOOH-BP), 3-acetylbenzophenone (AcBP), and 3-ethylbenzophenone (EtBP), as identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high-resolution mass spectrometry (HRMS). The presence of O₂ significantly affected the evolution of photoproducts during KTF photolysis. The photophysical properties of EtBP and AcBP were characterized by spectroscopic approaches. In particular, transient absorption spectra obtained by nanosecond laser flash photolysis (LFP) indicated that EtBP and AcBP were excited to triplet states with lifetimes of 28 and 2.4 µs, respectively. EtBP underwent further photodegradation, giving rise to EtOH-BP, EtOOH-BP, and AcBP upon UV₃₆₅ irradiation. The reaction is proposed to proceed through an excimer precursor (³[EtBP···EtBP]*) followed by intramolecular H-abstraction. In contrast, AcBP was relatively photostable, particularly under aerated condition. Both EtBP and AcBP have strong photosensitizing activity, as evidenced by the triplet probe 4-(N,N-dimethylamino)benzonitrile (DMABN). ECOSAR program suggested that the photoproducts are more ecotoxic and bioaccumulative than the parent KTF. Results of this study underscore the need to scrutinize the formation and fate of KTF photoproducts in sunlit surface waters.

Acidic Cannabinoid Decarboxylation

Introduction: Cannabis is a valuable plant, cultivated by humans for millennia. However, it has only been in the past several decades that biologists have begun to clarify the interesting Cannabis biosynthesis details, especially the production of its fascinating natural products termed acidic cannabinoids. Discussion: Acidic cannabinoids can experience a common organic chemistry reaction known as decarboxylation, transforming them into structural analogues referred to as neutral cannabinoids with far different pharmacology. This review addresses acidic and neutral cannabinoid structural pairs, when and where acidic cannabinoid decarboxylation occurs, the kinetics and mechanism of the decarboxylation reaction as well as possible future directions for this topic. Conclusions: Acidic cannabinoid decarboxylation is a unique transformation that has been increasingly investigated over the past several decades. Understanding how acidic cannabinoid decarboxylation occurs naturally as well as how it can be promoted or prevented during harvesting or storage is important for the various stakeholders in Cannabis cultivation.

Exploring the phototransformation and assessing the in vitro and in silico toxicity of a mixture of pharmaceuticals susceptible to photolysis

The present study comprehensively investigates the phototransformation and ecotoxicity of a mixture of twelve pharmaceutically active compounds (PhACs) susceptible to photolysis. Namely, three antibiotics (ciprofloxacin, levofloxacin, moxifloxacin), three antidepressants (bupropion, duloxetine, olanzapine), three anti-inflammatory drugs (diclofenac, ketoprofen, nimesulide), two beta-blockers (propranolol, timolol) and the antihistamine ranitidine were treated under simulated solar irradiation in ultra-pure and river water. A total of 166 different transformation products (TPs) were identified by ultra-high performance liquid chromatography coupled with Orbitrap high resolution mass spectrometry (UHPLC-Orbitrap HRMS), revealing the formation of twelve novel TPs and forty-nine not previously described in photolytic studies. The kinetic profiles of the major TPs resulting from a series of chemical reactions involving hydroxylation, cleavage and oxidation, dehalogenation, decarboxylation, dealkylation and photo substitution have been investigated and the transformation pathways have been suggested. Additionally, an in vitro approach to the toxicity assessment of daphnids was contrasted with ecotoxicity data based on the Ecological Structure Activity Relationships (ECOSAR) software comprising the in silico tool to determine the adverse effects of the whole mixture of photolabile parent compounds and TPs. The results demonstrated that photolysis of the target mixture leads to a decrease of the observed toxicity.

Ketoprofen affects swimming behavior and impairs physiological endpoints of Daphnia magna

Ketoprofen (KET) is a nonsteroidal anti-inflammatory and analgesic drug commonly used in human and veterinary medicine. This compound is detected in aquatic reservoirs however, little is known about its influence on cladocerans. Therefore, the aim of our study was to determine the influence of KET at concentrations of 0.005 mg/L, 0.05 mg/L, 0.5 mg/L, 5 mg/L and 50 mg/L on behavioral (swimming speed, hopping frequency) and physiological endpoints (heart rate, thoracic limb activity, mandible movements) of Daphnia magna after 24 h and 48 h exposure. The study showed that swimming speed frequency was decreased after 24 h and 48 h at all the concentrations used in the experiment. Hopping frequency was also inhibited, however the lowest amount of the drug induced transient increase of the parameter after 24 h and its subsequent decrease to the control level after 48 h. Although after 24 h of the exposure physiological parameters: heart rate, thoracic limb activity and mandible movements showed slightly lower sensitivity to KET than the behavioral endpoints: were found to be inhibited after 48 h. The results revealed that both behavioral and physiological endpoints of daphnids responded to KET also at the environmental level, therefore in natural conditions this drug should be considered as a hazardous toxicant to crustaceans.