New insights into the nature of short-lived paramagnetic intermediates of ketoprofen. Photo-CIDNP study

Photoinduced Processes in Lysine-Tryptophan-Lysine Tripeptide with L and D Tryptophan

Optical isomers of short peptide Lysine-Tryptophan-Lysine (Lys-{L/D-Trp}-Lys) and Lys-Trp-Lys with an acetate counter-ion were used to study photoinduced intramolecular and intermolecular processes of interest in photobiology. A comparison of L- and D-amino acid reactivity is also the focus of scientists' attention in various specialties because today, the presence of amyloid proteins with D-amino acids in the human brain is considered one of the leading causes of Alzheimer's disease. Since aggregated amyloids, mainly Aβ42, are highly disordered peptides that cannot be studied with traditional NMR and X-ray techniques, it is trending to explore the reasons for differences between L- and D-amino acids using short peptides, as in our article. Using NMR, chemically induced dynamic nuclear polarization (CIDNP) and fluorescence techniques allowed us to detect the influence of tryptophan (Trp) optical configuration on the peptides fluorescence quantum yields, bimolecular quenching rates of Trp excited state, and the photocleavage products formation. Thus, compared with the D-analog, the L-isomer shows a greater Trp excited state quenching efficiency with the electron transfer (ET) mechanism. There are experimental confirmations of the hypothesis about photoinduced ET between Trp and the CONH peptide bond, as well as between Trp and another amide group.

Stereoselectivity of Interaction of Nonsteroidal Anti-Inflammatory Drug S-Ketoprofen with L/D-Tryptophan in Phospholipid Membranes

The mechanisms of stereoselectivity of the interaction of chiral drugs with active sites of enzymes and cell receptors attract significant attention. The first reason is the difference in therapeutic activity of the enantiomers of the common drugs. Another reason is the interest in the role of chiral inversion of amino acids involved in various peptides in the development of many diseases including Alzheimer’s, Parkinson’s, type II diabetes, and a number of other pathological conditions. In our study we use elementary chemical process—electron transfer (ET) to simulate individual stages of ligand–receptor and enzyme–substrate interactions. In particular, previous studies of photoinduced ET in chiral donor-acceptor dyads consisting of the nonsteroidal anti-inflammatory drug (R/S)-ketoprofen and (L)-tryptophan show the stereo and spin selectivity of ET in diastereomers. The present study is devoted to the interaction of (S)-ketoprofen with L- and D-enantiomers of tryptophan in homogeneous aqueous solution and in phospholipid membranes. The study was done using the NMR technique and molecular modeling. These approaches confirm efficient penetration of ketoprofen into the lipid bilayer and binding with tryptophan molecule. The short-lived paramagnetic intermediates formed during the photoinduced ET from electron donor tryptophan to ketoprofen have been detected using the chemically induced dynamic nuclear polarization (CIDNP) technique. It was found that S-ketoprofen interacts stereoselectively with tryptophan enantiomers in the lipid membrane. The formation of the ketyl radical of ketoprofen under irradiation leads to the oxidation of membrane lipids and may be the cause of ketoprofen phototoxicity. However, in contrast to a homogeneous solution in phosphate buffer saline, where the amino acid tryptophan accelerates the photodecomposition of KP due to intramolecular hydrogen transfer, tryptophan in a lipid membrane significantly reduces the rate of photodegradation due to a reversible electron (or hydrogen) transfer reaction. The stereoselectivity in the rate of KP and lipids decomposition under UV irradiation of S-ketoprofen in the presence of tryptophan enantiomers in lipid bilayer has been detected.

Photoinduced Oxidation of Lipid Membranes in the Presence of the Nonsteroidal Anti-Inflammatory Drug Ketoprofen

The damage of cell membranes induced by photosensitive drugs has attracted the significant attention of researchers in various fields of medicine. Ketoprofen (KP) is known to be the most photosensitive among the nonsteroidal anti-inflammatory drugs. The phototoxic side effects of KP and other non-steroidal anti-inflammatory drugs are associated with the action of free radicals, but there is insufficient information about the nature of these radicals. In the present study, free radicals formed upon KP irradiation within lipid membranes were studied using nuclear magnetic resonance (NMR) and chemically induced dynamic nuclear polarization (CIDNP) methods, as well as a molecular dynamics simulation. Our study confirmed the effective penetration of KP into the lipid bilayer and showed a significant effect of the nature of the medium on the photolysis mechanism. While, in a homogeneous solution, the main channel of KP photolysis is free radical-mediated monomolecular decomposition with formation of radical pairs of benzyl and CO2H● radicals, then, in the lipid membrane, the reaction route shifts towards the bimolecular reaction of KP photoreduction. In addition, the effect of the presence an electron donor (the amino acid tryptophan) on lipid oxidation has been studied. It was found that photoreaction of KP with tryptophan proceeds more efficiently than with lipid molecules.

Comparative study of degradation of ketoprofen and paracetamol by ultrasonic irradiation: Mechanism, toxicity and DBP formation

The present study comparatively investigated the ultrasonic degradation of ketoprofen (KET) and paracetamol (PCT) in water. Ultrasonic irradiation at 555 kHz achieved rapid degradation of KET and PCT in water, the removal efficiencies of KET (2.5-80 μM) and PCT (2.5-80 μM) reached 87.7%-100% and 50.6%-86.9%, respectively, after 10 min of reaction under an ultrasonic power of 60 W. The degradation behaviors of both KET and PCT followed the Langmuir-Hinshelwood model. KET was eliminated faster than PCT because of its higher hydrophobicity. Acidic media favored ultrasonic degradation of KET and PCT. Organic compounds in water matrices exerted a great negative effect on the ultrasonic degradation rates of KET and PCT major by competing with target compounds with the generated radicals at the bubble/water interfacial region. The effects of anions were species dependent. The introduction of ClO4- and Cl- enhanced KET and PCT degradation to different extents, while the introduction of HCO3- posed a negative effect on both KET and PCT. KET and PCT degradation are accompanied by the generation of several transform intermediates, as identified via LC/MS/MS analysis, and corresponding reaction pathways have been proposed. A human umbilical vein endothelial cell (HUVEC) toxicity evaluation indicated that ultrasonic treatment was capable of controlling the toxicity of KET or PCT degradation. Of note, the enhanced formation of disinfection byproducts (DBPs), i.e., trichloromethane (TCM) and trichloronitromethane (TCNM), was found due to chlorination after ultrasonic treatment for both KET and PCT.

Comparative analysis on the photolysis kinetics of four neonicotinoid pesticides and their photo-induced toxicity to Vibrio Fischeri: Pathway and toxic mechanism

Neonicotinoids are widely used pesticides all over the world and pose severe water pollution. Although they can be degraded via absorbing sunlight, few attentions have been paid to the environmental risks of their photolysis products. In this paper, the photo-toxicity was investigated for four neonicotinoids (dinotefuran, nitenpyram, thiamethoxam and clothianidin) based on a series of experiments (i.e., photolysis kinetics, radical scavenging, bioluminescent inhibition test to Vibrio Fischeri and intermediate identification) and in-silico calculation of photolysis pathway. The results show that direct photolysis dominates the photolysis of the four neonicotinoids under simulated sunlight radiation. The bioluminescent inhibition kinetics shows that all four neonicotinoids have photo-induced toxicity to V. fischeri, but with different light-induced responses. Scavenging radicals (·OH and ¹O₂) will decrease the photo-induced toxicity of all the four neonicotinoids, indicating radicals play important roles to the photo-chemical reactions of intermediates. Dissolved organic matters exhibit slightly shading effect to the photolysis rates of four parent compounds. However, the ROSs generated by DOM can accelerate the photo-chemical reactions of intermediates, leading to different photo-induced toxicity in present of DOM. According to the detected intermediates and Gaussian calculations, there are different photolysis pathways and mechanisms for the four neonicotinoids. The calculation for photo-sensitization reactions with ³O₂ indicates that both energy transfer reactions and electron transfer reactions can be produced under simulated sunlight radiation, which further consolidate that reactive oxygen species are involved in the photolysis process. A theoretical model has been developed to explain the toxicity variations of four neonicotinoids in different aqueous conditions.

Photostabilization of ketoprofen by inclusion in glycyrrhizin micelles and gel nanoparticles

Ketoprofen (KP) is known to be the most photosensitive among the nonsteroidal anti-inflammatory drugs and may induce phototoxic and photoallergic reactions. Phototoxic side effects of KP are associated with the...