Degradation Mechanisms of 4,7-Dihydroxycoumarin Derivatives in Advanced Oxidation Processes: Experimental and Kinetic DFT Study

Influence of acid-base equilibrium on interactions of some monofunctional coumarin Pd(II) complexes with biologically relevant nucleophiles-comprehensive kinetic study

This aimed to develop a comprehensive theoretical protocol for examining substitution reaction processes. The researchers used a theoretical quantum-mechanical protocol based on the QM-ORSA approach, which estimates the kinetic parameters of thermodynamically favourable reaction pathways. This theoretical protocol was validated by experimentally investigating substitution mechanisms in two previously synthesised Pd(II) complexes: chlorido-[(3-(1-(2-hydroxypropylamino)ethylidene)chroman-2,4-dione)]palladium(II) (C1) and chlorido-[(3-(1-(2-mercaptoethylamino)-ethylidene)-chroman-2,4dione)]palladium(II) (C2), along with biologically relevant nucleophiles, namely L-cysteine (l-Cys), L-methionine (l-Met), and guanosine-5'-monophosphate (5'-GMP). Reactions were investigated under pseudo-first-order conditions, monitoring nucleophile concentration and temperature changes using stopped-flow UV-vis spectrophotometry. All reactions were conducted under physiological conditions (pH = 7.2) at 37 °C. The reactivity of the studied nucleophiles follows the order: l-Cys > l-Met > 5'-GMP, and the reaction mechanism is associative based on the activation parameters. The experimental and theoretical data showed that C2 is more reactive than C1, confirming that the complexes' structural and electronic properties greatly affect their reactivity with selected nucleophiles. The study's findings have confirmed that the primary interaction occurs with the acid-base species L-Cys, mostly through the involvement of the partially negative sulfur atom (87.2%). On the other hand, C2 has a higher propensity for reacting with L-Cys-, primarily through the partially negative oxygen atom (92.6%). The implementation of this theoretical framework will significantly restrict the utilization of chemical substances, hence facilitating cost reduction and environmental protection.

Exploring enzyme inhibition and comprehensive mechanisms of antioxidant/prooxidative activity of natural furanocoumarin derivatives: A comparative kinetic DFT study

This study aimed to explore the antioxidant and prooxidative activity of two natural furanocoumarin derivatives, Bergaptol (4-Hydroxy-7H-furo [3,2-g] [1]benzopyran-7-one, BER) and Xanthotoxol (9-Hydroxy-7H-furo [3,2-g] [1]benzopyran-7-one, XAN). The collected thermodynamic and kinetic data demonstrate that both compounds possess substantial antiradical activity against HO• and CCl3OO• radicals in physiological conditions. BER exhibited better antiradical activity in comparison to XAN, which can be attributed to the enhanced deprotonation caused by the positioning of the -OH group on the psoralen ring. In contrast to highly reactive radical species, newly formed radical species BER• and XAN• exhibited negligible reactivity towards the chosen constitutive elements of macromolecules (fatty acids, amino acids, nucleobases). Furthermore, in the presence of O2•─, the ability to regenerate newly formed radicals BER• and XAN• was observed. Conversely, in physiological conditions in the presence of Cu(II) ions, both compounds exhibit prooxidative activity. Nevertheless, the prooxidative activity of both compounds is less prominent than their antioxidant activity. Furthermore, it has been demonstrated that anionic species can engage in the creation of a chelate complex, which restricts the reduction of metal ions when reducing agents are present (O2•─ and Asc─). Moreover, studies have demonstrated that these chelating complexes can be coupled with other radical species, hence enhancing their ability to inactivate radicals. Both compounds exhibited substantial inhibitory effects against enzymes involved in the direct or indirect generation of ROS: Xanthine Oxidase (XOD), Lipoxygenase (LOX), Myeloperoxidase (MPO), NADPH oxidase (NOX).

Investigation of novel radical scavenging mechanisms in the alkaline environment: Green, sustainable and environmentally friendly antioxidative agent(s)

Pharmaceutical and industrial utilization of synthetic chemicals has an immerse impact on the environment. In that sense, novel chemicals with potential for industrial application should be investigated for their behaviour in reactions with hydroxyl radical, simulating AOPs (Advanced Oxidation Processes). AOPs are known for being highly effective in wastewater management and natural water remediation. In this paper, exhaustive research on the radical scavenging activity of a newly synthesized coumarin derivative (4HCBH), as a representative of the series of coumarin-benzohydrazides with high antioxidative potential was conducted. This study took into consideration the pH value range significant for practically all living organisms (pH = 7.0-8.5). According to the experimentally obtained results, the 4HCBH showed an increase in radical scavenging activity, following the slight increase in pH values, which suggested that the formation of anionic form of 4HCBH is responsible for its antiradical activity. Further investigations led to the postulation of a novel mechanistic approach called Sequential Proton Loss Electron Transfer - Radical-Radical Coupling (SPLET-RRC), in which, by a series of steps, a new, stable compound was formed. Furthermore, it was demonstrated that the product generated through SPLET-RRC showed lower toxicity than the parent molecule.

Recent advances in degradation of N,N-diethyl-3-toluamide (DEET)-an emerging environmental contaminant: a review

N,N-Diethyl-3-toluamide (DEET) is a commonly used insect repellent, which acts as an organic chemical contaminant in water and considered as an emerging contaminant which has been observed worldwide. It gets discharged into the environment through sewage waste. The various methods have been used to degrade DEET, such as UV based, ozonation, photocatalytic degradation, and biodegradation (based on the metabolic activity of fungi and bacteria). However, less research has been done on the degradation of DEET by deploying nanoparticles. Therefore, biodegradation and nanotechnology-based methods can be the potential solution to remediate DEET from the environment. This review is an attempt to analyze the routes of entry of DEET into the atmosphere and its environmental health consequences and to explore physical, chemical, and biological methods of degradation. Furthermore, it focuses on the various methods used for the biodegradation of the DEET, including their environmental consequences. Future research is needed with the application of biological methods for the degradation of DEET. Metabolic pathway for biodegradation was explored for the new potent microbial strains by the application of physical, chemical, and microbial genomics; molecular biology; genetic engineering; and genome sequencing methods.

Chitosan Hydrogels for Water Purification Applications

Chitosan-based hydrogels have gained significant attention for their potential applications in water treatment and purification due to their remarkable properties such as bioavailability, biocompatibility, biodegradability, environmental friendliness, high pollutants adsorption capacity, and water adsorption capacity. This article comprehensively reviews recent advances in chitosan-based hydrogel materials for water purification applications. The synthesis methods, structural properties, and water purification performance of chitosan-based hydrogels are critically analyzed. The incorporation of various nanomaterials into chitosan-based hydrogels, such as nanoparticles, graphene, and metal-organic frameworks, has been explored to enhance their performance. The mechanisms of water purification, including adsorption, filtration, and antimicrobial activity, are also discussed in detail. The potential of chitosan-based hydrogels for the removal of pollutants, such as heavy metals, organic contaminants, and microorganisms, from water sources is highlighted. Moreover, the challenges and future perspectives of chitosan-based hydrogels in water treatment and water purification applications are also illustrated. Overall, this article provides valuable insights into the current state of the art regarding chitosan-based hydrogels for water purification applications and highlights their potential for addressing global water pollution challenges.