Quantum chemical studies on molecular structure, AIM, ELF, RDG and antiviral activities of hybrid hydroxychloroquine in the treatment of COVID-19: Molecular docking and DFT calculations

Augmenting antioxidative capacity of myosin and cytoprotective potential of myosin digestion products through the integration of crocin and crocetin: A comprehensive analysis via quantum chemical computing and molecular dynamics

This study explores the binding properties of two important constituents from Crocus sativus L (crocin and crocetin) with myosin, examining their influence on antioxidant capacity in myosin and a grilled meat model. And their impact on cytoprotective potential of myosin digestion products was also assessed in Caco-2 cells. Crocin and crocetin exhibited discernible binding affinity to myosin via static quenching, which induced conformational alterations that bolstered the antioxidant capacity of myosin, preventing peroxidation, which also corroborated in a grilled meat model. Crocin resulted in greater enhancement of antioxidant capacity and binding affinity, as confirmed by quantum chemical calculations. Molecular dynamics simulations revealed the stable binding of crocin to GLU:272, GLU:606, GLN:628, and PHE:417 residues of myosin. In addition, crocin substantially enhanced the protective efficacy of myosin digestion products against H2O2-induced damage in Caco-2 cells by upregulating superoxide dismutase and GSH-Px and simultaneously downregulating reactive oxygen species and malondialdehyde levels.

Insight into the structural and dynamic properties of novel HSP90 inhibitors through DFT calculations and molecular dynamics simulations

CONTEXT

Heat-shock proteins (HSPs), particularly HSP90, are critical molecular chaperones that maintain protein stability, especially in cancer cells. Elevated HSP90 levels in tumors aid in oncogenic protein stabilization. This study focuses on developing potent, selective HSP90 inhibitors to disrupt its chaperone function, targeting cancer cell survival. Using a de novo hybridization approach, we designed novel inhibitors by integrating structural fragments from a known HSP90-binding drug, leading to the creation of hybrid compounds C1, C2, and C3. A 300 ns molecular dynamics simulation of each system revealed that C1, C2, and C3 formed more stable complexes with HSP90 compared to the reference compound, MEY. RMSD, RMSF, Rg, SASA, and MM-PBSA metrics supported these findings. DCCM and FEL analyses confirmed that the inhibitors did not alter HSP90's initial configuration. Further DFT calculations with the B3LYP/6-311 +  + (d,p) basis set were conducted to evaluate frontier molecular orbitals, MEP surfaces, ELF, LOL maps, TDOS and PDOS. The results indicated that C1, C2, and C3 formed more stable complexes with HSP90 compared to the reference compound MEY. These findings affirm the potential of C1, C2, and C3 as new anti-cancer therapies. Our approach demonstrates a promising strategy for developing selective HSP90 inhibitors that maintain the protein's functional integrity while disrupting its oncogenic role, paving the way for further preclinical evaluation of these novel compounds.

METHODS

Maestro 11.8, Discovery Studio Visualizer, Gromacs-2023, Gaussian 16, and online platforms like SwissADME and ProTox-II were utilized. Fragments generated from eight known HSP90-binding drugs were subjected to SP-docking, leading to 170 fragments. The highest-scoring fragments were merged using the breed panel to create new HSP90 inhibitors. XP-docking and ADMET analyses identified C1, C2, and C3 as the most promising candidates. These compounds were selected for a 300 ns dynamic simulation and subsequent DFT calculations.

The molecular structure, vibrational spectra, solvation effect, non-covalent interactions investigations of psilocin

Psilocin, or 4-HO-DMT (or 3-(2-dimethylaminoethyl)-1H-indol-4-ol), is a psychoactive alkaloid substance from the tryptamine family, isolated from Psilocybe mushrooms. This substance is being studied by various research groups because it has a clear therapeutic effect in certain dosages. In this work, the study of the structure and properties of psilocin was carried using theoretical methods: the effects of polar solvents (acetonitrile, dimethylsulfoxide, water, and tetrahydrofuran) on the structural parameters, spectroscopic properties (Raman, IR, and UV-Vis), frontier molecular orbital (FMO), molecular electrostatic potential (MEP) surface, and nonlinear optical parameters (NLO). Theoretical calculations were performed at the B3LYP/6-311++G(d,p) level by the density functional theory (DFT) method. IEFPCM was used to account for solvent effects. The types and nature of non-covalent interactions (NCI) between psilocin and solvent molecules were determined using Atoms in Molecules (AIM), the reduced density gradient method (RDG), the electron localization function (ELF), and the localization orbital locator (LOL). Experimental and calculated FT-IR, FT-Raman, and UV-Vis spectra were compared and found to be in good agreement.

Mapping the Interaction Landscape of Adenosine and Minoxidil Sulfate Using an Independent Gradient Model Based on Hirshfeld Partition and Interaction Region Indicator

Using theoretical techniques, the interactions between adenosine (AD) and minoxidil sulfate (MS) were studied using the DFT/M06-2X/aug-cc-pVDZ level of theory. The formation of the complex was thermodynamically favorable, so we carried out further studies. Frontier molecular orbital analysis shows that the HOMO-LUMO- gap is high (6.81 eV), which means that the complex is kinetically stable. The global reactivity parameters were also calculated to get insight about the chemical reactivity of the complex. Molecular electrostatic potential and charge analyses were carried out for the optimized complex. To study the charge transfer and inter- and intramolecular interactions present in the complex molecule, we employed natural bond orbital analysis. Noncovalent interaction (NCI) analysis along with IGMH and IRI analyses further helped us find the weak interactions. The presence of hydrogen bonds between the N atom (N27) of MS and H atom (H66) of AD and O atom (O32) of MS and H atom (H46) of AD was the main finding of these analyses. QTAIM investigation also supports this finding. EDA analysis was carried out to further study the intermolecular interactions present within the complex. Thus, the present investigation unveils the existence of weak NCIs in the complex.

Exploring Nano-optical Molecular Switch Systems for Potential Electronic Devices: Understanding Electric and Electronic Properties through DFT-QTAIM Assembly

The design and synthesis of molecular nanoswitches using organic molecules represent a crucial research field within molecular electronics. To understand the switching mechanisms, it is essential to investigate various factors, such as charge/energy transfer, electron transfer, nonlinear optical properties (NLO), current-voltage (I-V) curves, Joule-like (LJL) and Peltier-like (LPL) intramolecular phenomenological coefficients, as well as the energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) boundary orbitals. In this Article, a novel approach to designing a molecular nanoswitch and understanding its ON/OFF mechanism is presented, utilizing the quantum theory of atoms in molecules (QTAIM), density functional theory (DFT), and Landauer theory (LT). These analyses contribute significantly to a deep understanding of switching effects within molecular electronic systems.

Molecular interactions of the Omicron, Kappa, and Delta SARS-CoV-2 spike proteins with quantum dots of graphene oxide

CONTEXT

The Omicron, Kappa, and Delta variants are different strains of the SARS-CoV-2 virus. Graphene oxide quantum dots (GOQDs) represent a burgeoning class of oxygen-enriched, zero-dimensional materials characterized by their sub-20-nm dimensions. Exhibiting pronounced quantum confinement and edge effects, GOQDs manifest exceptional physical-chemical attributes. This study delves into the potential of graphene oxide quantum dots, elucidating their inherent properties pertinent to the surface structures of SARS-CoV-2, employing an integrated computational approach for the repositioning of inhibitory agents.

METHODS

Following rigorous adjustment tests, a spectrum of divergent bonding conformations emerged, with particular emphasis placed on identifying the conformation exhibiting optimal adjustment scores and interactions. The investigation employed molecular docking simulations integrating affinity energy evaluations, electrostatic potential clouds, molecular dynamics encompassing average square root calculations, and the computation of Gibbs-free energy. These values quantify the strength of interaction between GOQDs and SARS-CoV-2 spike protein variants. The receptor structures were optimized using the CHARM-GUI server employing force field AMBERFF14SB. The algorithm embedded in CHARMM offers an efficient interpolation scheme and automatic step size selection, enhancing the efficiency of the optimization process. The 3D structures of the ligands are constructed and optimized with density functional theory (DFT) method based on the most stable conformer of each binder. Autodock Vina Software (ADV) was utilized, where essential parameters were specified. Electrostatic potential maps (MEPs) provide a visual depiction of molecules' charge distributions and related properties. After this, molecular dynamics simulations employing the CHARM36 force field in Gromacs 2022.2 were conducted to investigate GOs' interactions with surface macromolecules of SARS-CoV-2 in an explicit aqueous environment. Furthermore, our investigation suggests that lower values indicate stronger binding. Notably, GO-E consistently showed the most negative values across interactions with different variants, suggesting a higher affinity compared to other GOQDs (GO-A to GO-D).

Various techniques for resolving overlapping ultraviolet spectra of combination pharmaceutical dosage forms containing hydroxychloroquine and paracetamol

Ten novel spectrophotometric approaches were developed for the initial examination of the Hydroxychloroquine and Paracetamol medications. These procedures are straightforward, specific, easy to use, and provide exact and accurate results. The determination was conducted through the utilization of several approaches, including zero order (dual wavelength, zero crossing, advanced absorption subtraction and spectrum subtraction), derivative (first derivative of zero crossing), ratio (ratio difference, ratio derivative) and mathematical (bivariate, simultaneous equation, and Q-absorbance) techniques. After undergoing validation in accordance with ICH criteria, it was established that each of these methods achieved acceptable levels of precision, repeatability, robustness, and accuracy. The advantages and disadvantages of each method are demonstrated, and the proposed and reported methodologies were statistically compared.

Synthesis, characterization, DFT studies and evaluation of the potential anti-tumour activity of nicotinic hydrazide based Schiff base using in vitro and molecular docking techniques

Breast cancer, one of the most serious issues worldwide, has been raising day by day. It has now become a necessary to develop a suitable drug to combat this terrible illness. Schiff bases are increasingly being used as powerful medications for a number of illnesses. BNH has now synthesized from Benzil and Nicotinic hydrazide and characterized experimentally by FT-IR, UV, 1H NMR,13CNMR and Mass analysis. DFT calculations were done using Gaussian 16 W with B3LYP/6-311 + G (d,p) and geometry of the compound is optimized. Frontier Molecular orbit (FMO), Mullikan atomic charges and Molecular Electrostatic Potential (MEP) were studied. Invitro antimicrobial studies were done using various bacteria and fungi. The synthesized compound is appropriate against bacterial and fungal actions. Invitro study were done using MCF-7 cell lines to analyze the anticancer property of the ligand. The outcome suggests that BNH may be employed in the future as a novel anticancer medication.

Unlocking the secrets of doxepin hydrochloride's crystal structure: Insights from high-quality powder diffraction analysis

Doxepin hydrochloride, a versatile pharmaceutical compound, has been the subject of extensive research aimed at elucidating its crystal structure and solid-state characteristics. In this manuscript, we explore the significance of high-quality powder diffraction data in unveiling the intricate details of doxepin hydrochloride's crystal lattice. By examining the refined atom coordinates, density functional theory (DFT) optimization, and intermolecular interactions, we gain valuable insights into its structural conformation. This knowledge highlights the importance of precise crystallographic data in advancing our understanding of complex compounds and their pharmaceutical applications.

Molecular simulation of Cu, Ag, and Au-decorated Si-doped graphene quantum dots (Si@QD) nanostructured as sensors for SO2 trapping

In view of the numerous environmental hazards and health challenges linked to sulfur (iv) oxide (SO2), an indirect greenhouse gas, and the resultant need to develop efficient gas nanosensor devices, this research had as its principal focus on the theoretical evaluation of the gas sensing potential of metals: Ag, Au and Cu functionalized silicon-doped quantum dots (Si@QD) for the detection and adsorption of SO2 gas investigated using the first-principles density functional theory (DFT) computation at the B3LYP-D3(BJ)/def2-SVP level of theory. Eight (8) possible adsorption modes: SO2_O_Si@QD, SO2_O_Ag_Si@QD, SO2_O_Au_Si@QD, SO2_O_Cu_Si@QD, SO2_S_Si@QD, SO2_S_Ag_Si@QD, SO2_S_Au_Si@QD, and SO2_S_Cu_Si@QD were considered based on SO2 interactions with the studied materials at the -S and -O sites of the SO2 molecule. The counterpoise correction (BSSE) showed that five of the eight interactions had favorable Ead + BSSE values ranging from -0.31 to -1.98 eV. All the eight interactions were observed to be thermodynamically favorable with ΔG and ΔH ranging from -129.01 to -200.24 kcal/mol and -158.26 to -229.73 kcal/mol respectively. Results from the topology analysis reveal that van der Waals forces occurred the greatest at the gas-sensor interphase while SO2_S_ Cu_Si@QD is predicted to have the highest sensing potency based on the conductivity and recovery time estimations. These results confirm the potential efficient feasibility of real-world device application of the metals (Ag, Au, Cu) functionalized Si-doped QDs.

Structural, electronic, intermolecular interaction, reactivity, vibrational spectroscopy, charge transfer, Hirshfeld surface analysis, pharmacological and hydropathy plot on 5-Bromo nicotinic acid - Antiviral study (Hepatitis A, B, and C)

The therapeutic properties of 5-Bromonicotinatic acid (5BNA) were studied for antiviral illnesses like Hepatitis A, Hepatitis B and Hepatitis C and the influence of electron-donating and electron-withdrawing properties of functional groups on the nicotinic acid was evaluated and represented in this study using the DFT approach. The molecular parameters were determined for both gases as well as for various solvent phases. The reactive areas in the compound are examined utilising Fukui analysis. The molecular interactions are accomplished by recognising the different types of bonding found in the compound using the AIM, ELF, LOL, RDG and IRI. Solvation investigations were demonstrated to have an influence on molecular orbital energy, ESP, UV-Vis and NLO analyses. Electron-hole, NBO and Hirshfeld investigations are used to investigate the transfer of charges and interactions inside the molecule. The method of vibrational spectroscopy (IR and Raman) is used to differentiate and identify the various types of vibrations displayed by the compound. The hydropathy plots for the proteins 2A4O, 6CWD and 2OC8 associated with Hepatitis A, Hepatitis B and Hepatitis C illustrate the disquiet and attraction of the amino acids towards the water.

Design, synthesis, and computational studies of novel imidazo[1,2-a]pyrimidine derivatives as potential dual inhibitors of hACE2 and spike protein for blocking SARS-CoV-2 cell entry

In the present work, a new series of imidazo[1,2-a]pyrimidine Schiff base derivatives have been obtained using an easy and conventional synthetic route. The synthesized compounds were spectroscopically characterized using ¹H, ¹³C NMR, LC-MS(ESI), and FT-IR techniques. Green metric calculations indicate adherence to several green chemistry principles. The energy of Frontier Molecular Orbitals (FMO), Molecular Electrostatic Potential (MEP), Quantum Theory of Atoms in Molecules (QTAIM), and Reduced Density Gradient (RDG) were determined by the Density Functional Theory (DFT) method at B3LYP/6-31 G (d, p) as the basis set. Moreover, molecular docking studies targeting the human ACE2 and the spike, key entrance proteins of the severe acute respiratory syndrome coronavirus-2 were carried out along with hACE2 natural ligand Angiotensin II, the MLN-4760 inhibitor as well as the Cannabidiolic Acid CBDA which has been demonstrated to bind to the spike protein and block cell entry. The molecular modeling results showed auspicious results in terms of binding affinity as the top-scoring compound exhibited a remarkable affinity (-9.1 and -7.3 kcal/mol) to the ACE2 and spike protein respectively compared to CBDA (-5.7 kcal/mol), the MLN-4760 inhibitor (-7.3 kcal/mol), and angiotensin II (-9.2 kcal/mol). These findings suggest that the synthesized compounds may potentially act as effective entrance inhibitors, preventing the SARS-CoV-2 infection of human cells. Furthermore, in silico, ADMET, and drug-likeness prediction expressed promising drug-like characteristics.

Exploration of intramolecular charge transfer in para-substituted nitrobenzofurazan: Experimental and theoretical analyses

The present work aims at exploring the high electrophilic character of 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) toward the morpholine group by an S_NAr reaction in acetonitrile or water (thereafter referred to as NBD-Morph). The electron-donating ability of the morpholine causes intra-molecular charge transfer (ICT). In this report, we present a comprehensive study on the optical characteristics using UV-Vis, photoluminescence (cw-PL) and its time-resolved (TR-PL) to determine the properties of the emissive intramolecular charge transfer (ICT) in the NBD-Morph donor-acceptor system. An exhaustive theoretical investigation utilizing the density functional theory (DFT) and its extension TD-DFT methods is an essential complement of experiments to rationalize and understand the molecular structure and related properties. The findings from QTAIM, ELF, and RDG analyses establish that the bonding between morpholine and NBD moieties is of the electrostatic or hydrogen bond type. In addition, the Hirshfeld surfaces have been established to explore the types of interactions. Further, the non-linear optical (NLO) responses of the compound have been examined. The structure-property relationships obtained through the combined experimental and theoretical offer valuable insights for designing efficient NLO material.

Conception of Cellulose/Alginate/Mesalazine microspheres by solvent evaporation technique for drug release: Experimental and theoretical investigations

Preparation of microspheres containing Mesalazine referred to as 5-aminosalicylic acid (5-ASA) for colon targeting drug was carried out using the emulsion solvent evaporation technique. The formulation was based on 5-ASA as the active agent, sodium Alginate (SA) andEthylcellulose (EC) as encapsulating agents, with polyvinyl alcohol (PVA) as emulsifier. The effects ofthe following processing parameters, 5-ASA %, EC:SA ratio and stirring rate on the properties of the resulting products in the form microspheres were considered. The samples were characterized using Optical microscopy, SEM, PXRD, FTIR, TGA, and DTG. In vitro release of 5-ASA from the different batches of microspheres was tested in biologically simulated fluids, (gastric; SGF, pH 1.2 for 2 h), then (intestinal fluid SIF, pH 7.4for 12 h) at 37 °C. The release kinetic results have been treated mathematically relaying on Higuchi's and Korsmeyer-Peppas' models for drug liberation. DOE study was performed to evaluate the interactive effects of variables on the drug entrapment and microparticle sizes. Molecular chemical interactions in structures were optimized using DFT analysis.

Structure-activity relationships and the underlying mechanism of α-amylase inhibition by hyperoside and quercetin: Multi-spectroscopy and molecular docking analyses

Inhibiting the activity of α-amylase has been considered an effective strategy to manage hyperglycemia. Hyperoside and quercetin are the main natural flavonoids in various plants, and the inhibition mechanism on α-amylase remains unclear. In this study, the structure-activity relationships between hyperoside/quercetin and α-amylase were evaluated by enzyme kinetic analysis, multi-spectroscopic techniques, and molecular docking analysis. Results showed that hyperoside and quercetin exhibited significant α-amylase inhibitory activities with IC₅₀ values of 0.491 and 0.325 mg/mL, respectively. The α-amylase activity decreased in the presence of hyperoside and quercetin in a competitive and noncompetitive manner, respectively. UV-vis spectra suggested that the aromatic amino acid residues (Trp and Tyr) microenvironment of α-amylase changed in the presence of these two flavonoids. FTIR and CD spectra showed the vibrations of the amide bands and the secondary structure content changes. The fluorescence quenching mechanism of α-amylase by hyperoside and quercetin belonged to the static quenching type. Finally, molecular docking intuitively showed that hyperoside/quercetin formed hydrogen bonds with the key active site residues (Asp197, Glu233, and Asp300) in α-amylase. MD simulation indicated hyperoside/quercetin-α-amylase docked complexes had good stability. Taken together, this research provides new sights to developing potent drugs or functional foods with hyperoside and quercetin, offering new avenues for hyperglycemia treatment.

Computational studies of the CuAAC reaction mechanism with diimine and phosphorus ligands for the synthesis of 1,4-disubstituted 1,2,3-triazoles

The Cu(i)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions with diimine and phosphorus ligands have been studied using DFT calculations in order to understand the effect of the nature of the ligands on the catalytic cycle for the formation of the 1,4-regioisomer.

B- and Al-Doped Porous 2D Covalent Organic Frameworks as Nanocarriers for Biguanides and Metformin Drugs

Nanostructures such as nanosheets, nanotubes, nanocages, and fullerenes have been extensively studied as potential candidates in various fields since the advancement of nanoscience. Herein, the interaction between biguanides (BGN) and metformin (MET) on the modified covalent organic framework (COF), COF-B, and COF-Al was investigated using density functional theory at the ωB97XD/6-311+G (d, p) level of computation to explore a new drug delivery system. The electronic properties evaluation reveals that the studied surfaces are suited for the delivery of both drug molecules. The calculated adsorption energies and basis set superposition errors (BSSE) ranged between -21.20 and -65.86 kJ/mol. The negative values obtained are an indication of excellent interaction between the drug molecules and the COF surfaces. Moreover, BGN is better adsorbed on COF-B with E_ads of -65.86 kJ/mol, while MET is better adsorbed on COF-Al with E_ads = -47.30 kJ/mol. The analysis of the quantum theory of atom in molecules (QTAIM) explained the nature and strength of intermolecular interaction existing between the drug molecules BGN and MET with the adsorbing surfaces. The analysis of noncovalent interaction (NCI) shows a weak hydrogen-bond interaction. Other properties such as quantum chemical descriptors and natural bond orbital (NBO) analysis also agree with the potential of COF surfaces as drug delivery systems. The electron localization function (ELF) is discussed, and it confirms the transitions occurring in the NBO analysis of the complexes. In conclusion, COF-B and COF-Al are suitable candidates for the effective delivery of BGN and MET.

Theoretical Study on Spectrum and Luminescence Mechanism of Indocyanine Green Dye Based on Density Functional Theory (DFT)

Indocyanine green is a great near-infrared fluorescence with good luminescent properties and important medical applications. In this paper, the theoretical spectrum and orbital model of its molecular level are established. The two most probable conformations were studied, and their energies, vibrational spectra, UV-Vis absorption spectra, frontier molecular orbitals (HOMO and LUMO), and energy gaps were obtained by density functional theory (DFT) calculations, respectively. This provides a theoretical and design basis for the development of novel dyes similar to indocyanine green dyes and a reference case for improved application methods and synthetic predesign of novel fluorescent dyes.

A Comprehensive Study of N-Butyl-1H-Benzimidazole

Imidazole derivatives have found wide application in organic and medicinal chemistry. In particular, benzimidazoles have proven biological activity as antiviral, antimicrobial, and antitumor agents. In this work, we experimentally and theoretically investigated N-Butyl-1H-benzimidazole. It has been shown that the presence of a butyl substituent in the N position does not significantly affect the conjugation and structural organization of benzimidazole. The optimized molecular parameters were performed by the DFT/B3LYP method with 6-311++G(d,p) basis set. This level of theory shows excellent concurrence with the experimental data. The non-covalent interactions that existed within our compound N-Butyl-1H-benzimidazole were also analyzed by the AIM, RDG, ELF, and LOL topological methods. The color shades of the ELF and LOL maps confirm the presence of bonding and non-bonding electrons in N-Butyl-1H-benzimidazole. From DFT calculations, various methods such as molecular electrostatic potential (MEP), Fukui functions, Mulliken atomic charges, and frontier molecular orbital (HOMO-LUMO) were characterized. Furthermore, UV-Vis absorption and natural bond orbital (NBO) analysis were calculated. It is shown that the experimental and theoretical spectra of N-Butyl-1H-benzimidazole have a peak at 248 nm; in addition, the experimental spectrum has a peak near 295 nm. The NBO method shows that the delocalization of the aσ-electron from σ (C1-C2) is distributed into antibonding σ* (C1-C6), σ* (C1-N26), and σ* (C6-H11), which leads to stabilization energies of 4.63, 0.86, and 2.42 KJ/mol, respectively. Spectroscopic investigations of N-Butyl-1H-benzimidazole were carried out experimentally and theoretically to find FTIR vibrational spectra.

A study of impurities in the repurposed COVID-19 drug hydroxychloroquine sulfate using ultra-high-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry and liquid chromatography-solid-phase extraction-nuclear magnetic resonance

RATIONALE

Hydroxychloroquine sulfate is effective in the treatment of malaria and autoimmune diseases and as an antiviral drug. However, unreported impurities are often detected in this drug, which pose a health risk. In this study, the structures of hydroxychloroquine and six unknown impurities were analyzed using ultra-high-performance liquid chromatography-quadrupole/time-of-flight-tandem mass spectrometry (UHPLC-Q/TOF/MS/MS), and the structures were characterized using liquid chromatography-solid-phase extraction-nuclear magnetic resonance (LC-SPE-NMR) spectroscopy.

METHODS

An Agilent InfinityLad Poroshell HPH-C18 column (100 × 4.6 mm, 2.7 μm) was used. For the analysis of hydroxychloroquine and six unknown impurities, the mobile phase was 20 mM ammonium formate aqueous solution and methanol/acetonitrile (80:20, v/v) using gradient elution. Full-scan MS and MS² were performed to obtain as much structural information as possible. In addition, six unknown impurities were separated by semi-preparative liquid chromatography and characterized using LC-SPE-NMR.

RESULTS

The MS² fragmentation patterns of the impurities were investigated, leading to more structural information and an understanding of the fragmentation pathways of the impurities. The structures of the unknown impurities were confirmed using NMR. In addition, some possible pathways of the formation of the impurities in the drugs were outlined, and these impurities were found to be process impurities.

CONCLUSIONS

Based on the identification and characterization of these impurities, this study also describes the cause of the production of the impurities and provides insights for companies to improve their production processes and a scientific basis for the improvement of the related pharmacopoeias.

Facile synthesis, crystal structure, biological evaluation, and molecular modeling studies of N-((4-acetyl phenyl) carbamothioyl) pivalamide as the multitarget-directed ligand

The crystal structure of N-((4-acetylphenyl)carbamothioyl)pivalamide (3) was synthesized by inert refluxing pivaloyl isothiocyanate (2) and 4-aminoacetophenone in dry acetone. The spectroscopic characterization (¹H-NMR, ¹³CNMR, FT-IR) and single crystal assays determined the structure of synthesized compound (3). Systematic experimental and theoretical studies were conducted to determine the molecular characteristics of the synthesized crystal. The biological examination of (3) was conducted against a variety of enzymes i.e., acetyl cholinesterase (AChE), butyl cholinesterase (BChE), alpha amylase, and urease enzyme were evaluated. The crystal exhibited approximately 85% enzyme inhibition activity against BChE and AChE, but only 73.8 % and 57.9% inhibition activity against urease and alpha amylase was observed respectively. The theoretical calculations were conducted using density functional theory studies (DFTs) with the 6–31G (d, p) basis set and B3LYP functional correlation. The Frontier molecular orbital analysis revealed that the HOMO/LUMO energy gap was smaller, which corresponds to the molecule’s reactivity. In terms of reactivity, the chemical softness value was found to be in good agreement with experimental values. In Crystal structure analysis, the intramolecular N—H•••O hydrogen bond generates a S 6) ring motif and N—H•••O interactions exist in crystal structure between the centroids of neighboring parallel aromatic (C4-C9) rings with a centroid to centroid distance of 3.9766 (7)Å. These intermolecular interactions were useful in structural stabilization. The Hirshfeld surfaces and their related two-dimensional fingerprint plots were used for thorough investigation of intermolecular interactions. According to Hirshfeld surface analysis of the crystal structure the most substantial contributions to the crystal packing are from H ••• O and H ••• N/N ••• H interactions. Molecular docking studies were conducted to evaluate the binding orientation of synthesized crystal with multiple targets. The compound exhibited stronger interactions with AChE and BChE with binding energies of -7.5 and -7.6 kcal/mol, respectively. On the basis of in-vitro and in-silico findings, it is deduced that N-((4-acetylphenyl)carbamothioyl)pivalamide 3) possesses reactive and potent multiple target inhibitory properties.

Application of DFT Calculations in Designing Polymer-Based Drug Delivery Systems: An Overview

Drug delivery systems transfer medications to target locations throughout the body. These systems are often made up of biodegradable and bioabsorbable polymers acting as delivery components. The introduction of density functional theory (DFT) has tremendously aided the application of computational material science in the design and development of drug delivery materials. The use of DFT and other computational approaches avoids time-consuming empirical processes. Therefore, this review explored how the DFT computation may be utilized to explain some of the features of polymer-based drug delivery systems. First, we went through the key aspects of DFT and provided some context. Then we looked at the essential characteristics of a polymer-based drug delivery system that DFT simulations could predict. We observed that the Gaussian software had been extensively employed by researchers, particularly with the B3LYP functional and 6-31G(d, p) basic sets for polymer-based drug delivery systems. However, to give researchers a choice of basis set for modelling complicated organic systems, such as polymer-drug complexes, we then offered possible resources and presented the future trend.

A computational study of potential therapeutics for COVID-19 invoking conceptual density functional theory

The pandemic, COVID-19, has caused social and economic disruption at a larger pace all over the world. Identification of an effective drug for the deadliest disease is still an exigency. One of the most promising approaches to combat the lethal disease is use of repurposed drugs. This study provides insights into some of the potential repurposed drugs viz. camostat mesylate, hydroxychloroquine, nitazoxanide, and oseltamivir in terms of the computational quantum chemical method. Properties of these compounds have been elucidated in terms of Conceptual Density Functional Theory (CDFT)-based descriptors, IR spectra, and thermochemical properties. Computed results specify that hydroxychloroquine is the most reactive drug among them. Thermochemical data reveals that camostat mesylate has the utmost heat capacity, entropy, and thermal energy. Our findings indicate that camostat mesylate and hydroxychloroquine may be investigated further as potential COVID-19 therapeutics. We anticipate that the current study will aid the scientific community to design and develop viable therapeutics against COVID-19.

Application of Mathematical Modeling and Computational Tools in the Modern Drug Design and Development Process

The conventional drug discovery approach is an expensive and time-consuming process, but its limitations have been overcome with the help of mathematical modeling and computational drug design approaches. Previously, finding a small molecular candidate as a drug against a disease was very costly and required a long time to screen a compound against a specific target. The development of novel targets and small molecular candidates against different diseases including emerging and reemerging diseases remains a major concern and necessitates the development of novel therapeutic targets as well as drug candidates as early as possible. In this regard, computational and mathematical modeling approaches for drug development are advantageous due to their fastest predictive ability and cost-effectiveness features. Computer-aided drug design (CADD) techniques utilize different computer programs as well as mathematics formulas to comprehend the interaction of a target and drugs. Traditional methods to determine small-molecule candidates as a drug have several limitations, but CADD utilizes novel methods that require little time and accurately predict a compound against a specific disease with minimal cost. Therefore, this review aims to provide a brief insight into the mathematical modeling and computational approaches for identifying a novel target and small molecular candidates for curing a specific disease. The comprehensive review mainly focuses on biological target prediction, structure-based and ligand-based drug design methods, molecular docking, virtual screening, pharmacophore modeling, quantitative structure-activity relationship (QSAR) models, molecular dynamics simulation, and MM-GBSA/MM-PBSA approaches along with valuable database resources and tools for identifying novel targets and therapeutics against a disease. This review will help researchers in a way that may open the road for the development of effective drugs and preventative measures against a disease in the future as early as possible.