Insights into the coordination mode of quercetin with the Al(III) ion from a combined experimental and theoretical study

An Update in Computational Methods for Environmental Monitoring: Theoretical Evaluation of the Molecular and Electronic Structures of Natural Pigment-Metal Complexes

Metals are beneficial to life, but the presence of these elements in excessive amounts can harm both organisms and the environment; therefore, detecting the presence of metals is essential. Currently, metal detection methods employ powerful instrumental techniques that require a lot of time and money. Hence, the development of efficient and effective metal indicators is essential. Several synthetic metal detectors have been made, but due to their risk of harm, the use of natural pigments is considered a potential alternative. Experiments are needed for their development, but they are expensive and time-consuming. This review explores various computational methods and approaches that can be used to investigate metal-pigment interactions because choosing the right methods and approaches will affect the reliability of the results. The results show that quantum mechanical methods (ab initio, density functional theory, and semiempirical approaches) and molecular dynamics simulations have been used. Among the available methods, the density functional theory approach with the B3LYP functional and the LANL2DZ ECP and basis set is the most promising combination due to its good accuracy and cost-effectiveness. Various experimental studies were also in good agreement with the results of computational methods. However, deeper analysis still needs to be carried out to find the best combination of functions and basis sets.

The potential biological effects of quercetin based on pharmacokinetics and multi-targeted mechanism in vivo

Quercetin is a plant-derived polyphenol flavonoid that has been proven to be effective for many diseases. However, the mechanism and in vivo metabolism of quercetin remains to be clarified. It achieves a wide range of biological effects through various metabolites, gut microbiota and its metabolites, systemic mediators produced by inflammation and oxidation, as well as by multiple mechanisms. The all-round disease treatment of quercetin is achieved through the organic combination of multiple channels. Therefore, this article clarifies the metabolic process of quercetin in the body, and explores the new pattern of action of quercetin in the treatment of diseases.

A Review on Coordination Properties of Al(III) and Fe(III) toward Natural Antioxidant Molecules: Experimental and Theoretical Insights

This review focuses on the ability of some natural antioxidant molecules (i.e., hydroxycinnamic acids, coumarin-3-carboxylic acid, quercetin, luteolin and curcumin) to form Al(III)- and Fe(III)-complexes with the aim of evaluating the coordination properties from a combined experimental and theoretical point of view. Despite the contributions of previous studies on the chemical properties and biological activity of these metal complexes involving such natural antioxidants, further detailed relationships between the structure and properties are still required. In this context, the investigation on the coordination properties of Al(III) and Fe(III) toward these natural antioxidant molecules might deserve high interest to design water soluble molecule-based metal carriers that can improve the metal’s intake and/or its removal in living organisms.

Oxidative Stress Evaluation in Ischemia Reperfusion Models: Characteristics, Limits and Perspectives

Ischemia reperfusion injury is a complex process consisting of a seemingly chaotic but actually organized and compartmentalized shutdown of cell function, of which oxidative stress is a key component. Studying oxidative stress, which results in an imbalance between reactive oxygen species (ROS) production and antioxidant defense activity, is a multi-faceted issue, particularly considering the double function of ROS, assuming roles as physiological intracellular signals and as mediators of cellular component damage. Herein, we propose a comprehensive overview of the tools available to explore oxidative stress, particularly in the study of ischemia reperfusion. Applying chemistry as well as biology, we present the different models currently developed to study oxidative stress, spanning the vitro and the silico, discussing the advantages and the drawbacks of each set-up, including the issues relating to the use of in vitro hypoxia as a surrogate for ischemia. Having identified the limitations of historical models, we shall study new paradigms, including the use of stem cell-derived organoids, as a bridge between the in vitro and the in vivo comprising 3D intercellular interactions in vivo and versatile pathway investigations in vitro. We shall conclude this review by distancing ourselves from "wet" biology and reviewing the in silico, computer-based, mathematical modeling, and numerical simulation options: (a) molecular modeling with quantum chemistry and molecular dynamic algorithms, which facilitates the study of molecule-to-molecule interactions, and the integration of a compound in a dynamic environment (the plasma membrane...); (b) integrative systemic models, which can include many facets of complex mechanisms such as oxidative stress or ischemia reperfusion and help to formulate integrated predictions and to enhance understanding of dynamic interaction between pathways.

Investigation of the deprotonation of tetracycline using differential absorbance spectra: A comparative experimental and DFT/TD-DFT study

Tetracycline is a type of broad-spectrum, naturally occurring antibiotic that leads to several side effects, such as affecting intestinal flora and increase in bacterial resistance. The affinity of tetracycline for abiotic and biotic surfaces and metal ions is closely related to its deprotonation state and charge distribution; however, its deprotonation-protonation property remains unclear. In this study, the hydrolysis of tetracycline was investigated by combining experiments with quantum-chemical calculations. The molecular structure of the probable deprotonation states were optimized by quantum-chemical calculations, and the corresponding absorbance spectra were predicted based on frontier molecular orbital (FMO) theory. The absorbance spectra showed structure-specific features at the different deprotonation states. In addition, changes in tetracycline absorbance spectra in the pH range of 2.00-12.00 was examined by spectroscopic titration. The deprotonation was found to proceed in the order of site 3, 4, 12, and 10, which was identified by comparing the quantum-chemical calculations and experimental differential absorbance spectra (DAS). The results in this study are of great significance for further studies of the transport and fate of tetracycline in the environment.

Direct Rapid Determination of Trace Aluminum in Various Water Samples with Quercetin by Reverse Phase High-Performance Liquid Chromatography Based on Fabric Phase Sorptive Extraction Technique

The determination of trace levels of aluminum by high-performance liquid chromatography (HPLC) with UV detection using quercetin, a natural bioactive flavonol, as a metal complexation agent is presented in the current article. The developed method has been successfully applied to the direct determination of aluminum in water samples collected from various sources. A preconcentration technique is indispensable due to the presence of aluminum in environmental water at trace levels. Fabric phase sorptive extraction (FPSE), a relatively new but promising sample preparation technique, was applied to preconcentrate quercetin-Al(III) complex from water samples. Efficient extraction of the quercetin-Al(III) complex from aqueous samples has been accomplished by applying FPSE using a cellulose fabric substrate coated with sol-gel C18 hybrid nanocomposite sorbent. Baseline separation of Al-quercetin complex has been achieved on a reverse phase C18 column with the use of acetonitrile: 3% acetic acid (30:70; v/v) as the mobile phase at a flow rate of 1.0 mL/min. The new FPSE-HPLC-UV method can be used for the routine screening of Al ions in various water samples with high sensitivity, precision and reliability.

Experimental and quantum-chemical study of differential absorbance spectra of environmentally relevant species: A study of quercetin deprotonation and its interactions with copper (II) ions

This study compared the experimental and theoretically calculated differential absorbance spectra (DAS) of quercetin, which is a typical model compound of natural organic matter (NOM) that is found in biochemical and environmental systems. Absorbance spectra of quercetin, which has five exchangeable protons, were generated at each state of deprotonation and its binding with Cu(II) ions. The spectra showed that the emergence of characteristic peaks in the experimental DAS was associated with the deprotonation of quercetin and its binding with Cu(II). Calculations of the theoretical DAS were conducted based on the time-dependent density functional theory (TD-DFT) methods and yielded results that were consistent with the experimental DAS data because the features in the absorbance spectra were primarily associated with the electron transitions from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) in the molecule. The appearance of the characteristic peaks in the DAS reflects the changes of the structure and electron distribution of the organic molecules that are induced by water treatment or environmental processes.

Complexation of luteolin with lead (II): Spectroscopy characterization and theoretical researches

The interactions of (CH₃COO)₂Pb·3H₂O (lead acetate trihydrate) with luteolin, 5,7,3',4'-tetrahydroxyflavone, were investigated in methanol solution. The spectroscopy (UV-Vis, FT-IR, HPLC-MS, ¹H NMR) and elemental analysis were adopted to assess the interaction of luteolin and Pb(II). The results show that luteolin reacts with Pb(II) through the chelating sites of 4‑carbonyl and 5-hydroxy in two luteolin molecules. The structures, energies, CDA (charge decomposition analysis) and orbitals analysis of the ligand and complex have been analyzed according to quantum-chemical calculation, which is further proofed that luteolin molecule can effectively chelate Pb(II) by 5-hydroxyl-4-oxo chelating site. It is speculated that luteolin has a high potential of becoming a health care product to eliminate lead cation in the future.

Development and characterization of antioxidant active packaging and intelligent Al3+-sensing films based on carboxymethyl chitosan and quercetin

Different amounts of quercetin were mixed with carboxymethyl chitosan (CMCS) to develop novel antioxidant active packaging and intelligent Al³⁺-sensing films. The physical properties, structure, antioxidant and Al³⁺-sensing abilities of CMCS-quercetin composite films were investigated. Results showed CMCS-quercetin composite films presented a dark yellowish color. When compared with CMCS film, CMCS-quercetin composite films containing 5 and 7.5 wt% of quercetin on CMCS basis exhibited higher thicknesses, opacity and thermal stability; however, presented lower moisture contents, UV-vis light transmittance and elongation at break. Besides, the incorporation of quercetin could not significantly change the water solubility and water vapor barrier property of CMCS film. Morphological observation showed the surface of CMCS-quercetin composite film became coarse when 7.5 wt% of quercetin was incorporated. Infrared spectra and X-ray diffraction patterns of CMCS-quercetin composite films further indicated quercetin was compatible with CMCS. Importantly, CMCS-quercetin composite films could sustainably release antioxidant ability into aqueous and fatty food stimulants. Moreover, CMCS-quercetin composite films were sensitive to Al³⁺. The color and UV-vis absorption patterns of CMCS-quercetin composite films were changed by the addition of Al³⁺. Results suggested that CMCS-quercetin composite films could be used as novel antioxidant and intelligent Al³⁺-sensing materials in food packaging.

Butan-1-ol as an extractant solvent in dispersive liquid-liquid microextraction in the spectrophotometric determination of aluminium

Determining aluminium ions at μg L^-1 scale currently requires either costly analytical techniques such as inductively coupled plasma, and/or graphite furnace atomic absorption spectrometry. Dispersive liquid-liquid microextraction (DLLME) is designed to promote separation and preconcentration, thus making it possible to determine the analyte of interest without significant matrix influence. This study was aimed at the development of a spectrophotometric method to determine Al³⁺ after microextraction of its complex with quercetin. Butan-1-ol was used as a novel extractant solvent in the DLLME process. The parameters influencing complexation and microextraction, such as the amount of quercetin and volume of extractant were evaluated by univariate analysis. In optimised conditions were estimated for the proposed method: linear range from 7.5 to 165.0 μg L^-1, LOD of 2.0 μg L^-1, and LOQ of 7.0 μg L^-1. The accuracy was checked by applying the proposed method to water (NIST SRM-1643e) and rice flour (NIST SRM-1568c) certified reference materials and spike-and-recovery trials with distinct samples (mineral water, green tea, thermal spring water, contact lens disinfecting solution, saline concentrate for hemodialysis and urine).

Study of Al3+ interaction with AMP, ADP and ATP in aqueous solution

The interaction of Al³⁺ and nucleotide ligands, namely adenosine-5'-monophosphate, (AMP), adenosine-5'-diphosphate, (ADP), adenosine-5'-triphosphate, (ATP), has been studied in aqueous solution at T = 298.15 K and I = 0.15 mol L^-1 in NaCl (only for Al³⁺-ATP system at I = 0.1 mol L^-1). Formation constants and speciation models for the species formed are discussed on the basis of potentiometric results. The speciation models found for the three systems include ML and ML₂ species in all the cases, and for Al³⁺-ADP and ATP systems, MLH, MLOH and ML₂OH species as well. The formation constant value for ML species shows the trend, AMP < ADP < ATP. ¹H NMR spectroscopy was also employed for the study of Al³⁺-ATP system. The ¹H NMR results are in agreement with the speciation model obtained from analysis of potentiometric titration data, confirming the stabilities of the main species. Enthalpy change values were obtained by titration calorimetry; for the main Al³⁺-ATP species (at T = 298.15 K and I = 0.1 mol L^-1 in NaCl), they resulted always higher than zero, as typical for hard-hard interactions. The dependence of formation constants on ionic strength over the range I = 0.1 to 1 mol L^-1 in NaCl is also reported for Al³⁺-ATP system. The sequestering ability of the nucleotides under study towards Al³⁺ was also evaluated by the empirical parameter pL_0.5.

Structural characterization of aluminium(iii) and iron(iii) complexes of coumarinic acid in aqueous solutions from combined experimental and theoretical investigations

The Al(iii) ion forms bidentate complexes involving a 6-membered ring by binding both the carboxyl oxygens of the ligand. In contrast, the Fe(iii) ion preferentially forms monodentate tetrahedral complexes.

Binding of Al(iii) to synthetic RNA and metal-mediated strand aggregation

Kinetic curve of the binding of aluminum to RNA and metal-induced strand aggregation.

Complexation behaviour of caffeic, ferulic and p-coumaric acids towards aluminium cations: a combined experimental and theoretical approach

The formation of complexes of hydroxycinnamic acids with Al(iii) ions is strongly pH-dependent and the complexation occurs via a carboxylic function.

Mass spectrometry and potentiometry studies of Al(iii)–naringin complexes

Here we have studied the complexation of naringin with Al(iii) under physiological conditions (i.e., at 37 °C and in 0.16 mol L⁻¹NaCl).

Properties and applications of flavonoid metal complexes

Flavonoid metal complexes have a wide spectrum of activities as well as potential and actual applications.

A rhodamine-based ‘turn-on’ Al3+ ion-selective reporter and the resultant complex as a secondary sensor for F− ion are applicable to living cell staining

A new cell permeable rhodamine based Schiff base (L) senses nanomolar level of Al³⁺ ions through CHEF process and its Al(iii) complex (2) behaves as a highly F⁻ ions selective biomarker through fluorescence quenching in HEPES buffer.