Optimized POCl3-assisted synthesis of 2-amino-1,3,4-thiadiazole/1,3,4-oxadiazole derivatives as anti-influenza agents

Although recent decades have witnessed the synthesis of 1,3,4-thiadiazoles via phosphorus POCl₃-promoted cyclization reaction, simultaneous access to 2-amino-1,3,4-thiadiazole and 2-amino-1,3,4-oxadiazole analogs remains unexpected and elusive. Herein, a detailed regiocontrolled synthesis of 2-amino-1,3,4-thiadiazoles in good to high yields with good regioselectivities from readily available thiosemicarbazides using POCl₃ was disclosed. Meantime, to establish a comprehensive structure–activity relationship, 2-amino-1,3,4-oxadiazole derivatives as single regioisomers were prepared via EDCI·HCl-triggered cyclization of the thiosemicarbazide intermediates. The in vitro anti-influenza assays proved that the selected compounds with the pyrazine/pyridine ring exhibited certain inhibitory activities against influenza A virus strains A/HK/68 (H3N2) and A/PR/8/34 (H1N1) in MDCK cells. Among them, N-(adamantan-1-yl)-5-(5-(azepan-1-yl)pyrazin-2-yl)-1,3,4-thiadiazol-2-amine (4j) was the most active compound, and exhibited favorable activity with EC₅₀ values of 3.5 μM and 7.5 μM, respectively. In addition, the molecular docking results explained the reason why compound 4j had dual inhibitory activity and revealed the reasonable binding mode of this compound with the M2-S31N and M2-WT ion channels. This compound had the potential to be further developed as an anti-influenza drug.     

Regio- and stereoselectivity of the 1,3-dipolar cycloaddition of azomethine ylides to (E)-3-(2-oxo-2-(pyren-1-yl)ethylidene)indolin-2-ones: A combined experimental and theoretical study

Functionalized oxindoles and pyrrolizidines form the central structural framework for numerous natural products with extensive biological and pharmacological applications. The requirement for high regio- and stereoselectivity is the main obstacle in the synthesis of such five-membered heterocycles. Multicomponent cycloaddition reactions often provide an efficient and straightforward approach for the preparation of specific regio- and stereoisomers. In this article, the regio- and stereochemistry of the polar [3 + 2]-cycloaddition (32CA) reaction of azomethine ylides prepared by the reaction of isatin derivatives and L-proline with a series of (E)-3-(2-oxo-2-(pyren-1-yl)ethylidene)indolin-2-ones was investigated by experimental and theoretical methods. Among the isatin and (E)-3-(2-oxo-2-(pyren-1-yl)ethylidene)indolin-2-one derivatives, a remarkable inversion of regioselectivity was observed in the 32CA reaction of azomethine ylide generated by the reaction of L-proline and 5-chloroisatin or N-methyl-5-chloroisatin with (E)-5-chloro-3-(2-oxo-2-(pyren-1-yl)ethylidene)indolin-2-one. The regio- and stereochemical assignment of the structures of the cycloaddition products was determined by one- and two-dimensional (1D&2D) homonuclear and heteronuclear correlation nuclear magnetic resonance spectroscopy. The molecular mechanism as well as the regio- and stereoselectivity of the cycloaddition were investigated by means of global and local reactivity indices and a density functional theory (DFT) and explained in detail on the basis of the transition state stabilities of the reactants.     

Synthesis of benzimidazole derivatives via reaction between aromatic amines and aldehydes: Structure determination and theoretical insights

The condensation reaction between primary amine and aromatic aldehyde or ketone ubiquitously synthesizes –C=N- function that appears in the Schiff bases. Presence of ortho –NH/NH₂ group may form a cyclic product which is further oxidized to generate –C=N- function. Herein, two quinoline based cyclic benzimidazole compounds, namely, 2-[1-(Phenyl-pyridin-2-yl-methyl)-1H-benzoimidazol-2-yl]-quinoline (L5) and 2-[1-(Phenyl-pyridin-2-yl-methyl)-1H-benzoimidazol-2-yl]-quinolin-8-ol (L6) are synthesized from o-phenylenediamine derivative [N¹-(phenyl(pyridin-2-yl)methyl)benzene-1,2-diamine] (L) via condensation followed by in-situ dehydrogenation. The structures of the products have been confirmed by the single crystal X-ray diffraction measurement and other physicochemical data. The intra- and intermolecular H-bonding, C–H ^… π interactions in the structures instigate supramolecular self-assembly. The DFT computation has been attempted to explain the formation of energy minimized cyclic product out of acyclic counterpart; the meticulous comparison of the present theoretical outcomes with that of previously reported o-phenylenediamine derivatives, further supports the formation of energy minimized products.     

Chemical and pharmacological aspects of novel hetero MLB complexes derived from NO2 type Schiff base and N2 type 1,10-phenanthroline ligands

A series of hetero ligand MLB complexes (1–5) were synthesised from tridentate NO₂ type Schiff base [H₂L: (E)-2-((2-hydroxy-4-methoxyphenyl)(phenyl)methyleneamino)benzoic acid; derived from 2-hydroxy-4-methoxybenzophenone and 2-aminobenzoic acid] and bidentate N₂ type 1,10-phenanthroline (B: phen) ligands. The structural characterization of the synthesised MLB complexes were carried out via analytical as well as various spectral studies. Additionally, the low molar conductance values (Λ_m = 14–22 Ω⁻¹ cm² mol⁻¹) imply that the complexes (1–5) are non-electrolytes. The obtained results reinforce that stoichiometry of the mononuclear hetero ligand complexes can be represented as [M(II)-Schiff base(L)-phen(B)·H₂O] and both H₂L and (B) ligands can act as tri and bidentates respectively. Moreover, both the ligands bind with metal(II) ions to build a stable six, six, five membered chelate rings with octahedral geometry. The existing solvent water molecule is confirmed from thermal as well as vibrational analysis. Their microcrystalline nature and uniform surface morphology were confirmed by both powder XRD and SEM studies. 3D molecular modeling and analysis of NiLB and CuLB complexes (3 and 4) were also studied. Mn(II), Ni(II) and Cu(II) complexes (1, 3 and 4) strongly interact with DNA through intercalation binding with strong binding constant values. The obtained K_app values were 5.23, 4.98, 6.36, 7.21 and 4.86 × 10⁵ mol⁻¹ for MLB complexes (1–5) respectively and the negative Δ³G values shown that all the complexes are strongly interact with DNA in a spontaneous manner. Further, remarkable biological, antioxidant and DNA activities were remarkably exhibited by MnLB, NiLB and CuLB complexes.     

QSAR based virtual screening derived identification of a novel hit as a SARS CoV-229E 3CLpro Inhibitor: GA-MLR QSAR modeling supported by molecular Docking,molecular dynamics simulation and MMGBSA calculation approaches

Congruous coronavirus drug targets and analogous lead molecules must be identified as quickly as possible to produce antiviral therapeutics against human coronavirus (HCoV SARS 3CLpro) infections. In the present communication, we bear recognized a HIT candidate for HCoV SARS 3CLpro inhibition. Four Parametric GA-MLR primarily based QSAR model (R2:0.84, R2adj:0.82, Q2loo: 0.78) was once promoted using a dataset over 37 structurally diverse molecules along QSAR based virtual screening (QSAR-VS), molecular docking (MD) then molecular dynamic simulation (MDS) analysis and MMGBSA calculations. The QSAR-based virtual screening was utilized to find novel lead molecules from an in-house database of 100 molecules. The QSAR-vS successfully offered a hit molecule with an improved _PEC₅₀ value from 5.88 to 6.08. The benzene ring, phenyl ring, amide oxygen and nitrogen, and other important pharmacophoric sites are revealed via MD and MDS studies. Ile164, Pro188, Leu190, Thr25, His41, Asn46, Thr47, Ser49, Asn189, Gln191, Thr47, and Asn141 are among the key amino acid residues in the S1 and S2 pocket. A stable complex of a lead molecule with the HCoV SARS 3CLpro was discovered using MDS. MM-GBSA calculations resulted from MD simulation results well supported with the binding energies calculated from the docking results. The results of this study can be exploited to develop a novel antiviral target, such as an HCoV SARS 3CLpro Inhibitor.     

Design,synthesis, biological activity evaluation and mechanism of action of myricetin derivatives containing thioether quinazolinone

Plant bacteria and viruses have a huge negative impact on food crops in the world. Therefore, it is important to create new and efficient green pesticides. In this paper, a series of myricetin derivatives containing quinazolinone sulfide were introduced. Good antibacterial and antiviral activities of the drug molecules 2-((3-((5,7-dimethoxy-4-oxo-2-(3,4,5-trimethoxyphenyl)-4H-chromen-3-yl)oxy)propyl)thio)-6-fluoro-3-phenylquinazolin-4(3H)-one (T5) and 2-((4-((5,7-dimethoxy-4-oxo-2-(3,4,5-trimethoxyphenyl)-4H-chromen-3-yl)oxy)butyl)thio)-6-methyl-3-phenylquinazolin-4(3H)-one (T15) respectively were found by biological activity screening. The value of dissociation constant (K_d) of compound T15 to TMV CP was 0.024 ± 0.006 μM, determined by Microscale thermophoresis (MST), which was far less than the value of 8.491 ± 2.027 μM of commercial drug ningnanmycin (NNM). The interaction between compound T15 and TMV CP was further verified by molecular docking. Compound T15 formed strong hydrogen bonds with residues SER:49 and SER:15 (1.92 Å, 2.20 Å, respectively), which were superior to the traditional hydrogen bonds formed by NNM with residue SER:215 (3.64 Å). In addition, the effects of compound T15 on the contents of chlorophyll and peroxidase (POD) in tobacco were studied, and the results indicated that compound T15 could enhance the disease resistance of tobacco plants to a certain extent.     

Molecular structure,spectroscopic, electronic and physicochemical properties of 7,8-dihydroxyflavone hydrate compound using first theory principle

The present investigation involves the structure-based drug design and the functional evaluation of flavone based compound that can be utilized for breast cancer therapy, and it provides a way to create platforms for chemotherapy of breast cancer treatments. The 7,8-dihydroxyflavone hydrate (7DHFH) molecule was structurally characterized by spectroscopic techniques such as FT-IR/Raman, and EPR spectral analysis, which were compared with the DFT methods using Gaussian09 software packages. The complete assignments of the fundamental vibrational modes were obtained using potential energy distribution.The DFT results show a good agreement with the all experimental results. A DFT study on frontier molecular orbital analysis is used to calculate the HOMO- LUMO energies and charge transfer or conjugative interaction taking place within the molecular system and also other molecular parameters, viz. chemical hardness, softness, ionization potential, electron affinity, electrophilicity index, and electronegativity. Furthermore, the drug likeness properties were also calculated, thus allowing us to identify the present compound as a potential anticancer agent. Molecular docking results revealed the bioactive candidate displayed the best free-energy score towards the target proteins through forming strong hydrogen bonds with the amino acid residues. Finally, the cytotoxic activity of the 7DHFH confirms the anticancer activity against human breast cancer cell lines by MTT assays.     

Investigating the binding measurements of human α-acid glycoprotein with chlorambucil and dacarbazine in the presence of imidazolium based -ionic liquid by affinity capillary electrophoresis

Human alpha (α1)-acid glycoprotein (AGP) is an acute phase protein whose plasma concentration increases several-folds in the presence of various diseases. The variability in AGP plasma concentration is expected to have a huge impact on the drug binding equilibrium. Therefore, a precise measurement of AGP-drug binding is of great demand for drug development. In the current study, an ionic liquid-based aqueous two-phase system combined with affinity capillary electrophoresis (ILATPS/ACE) was utilised in order to improve the accuracy of AGP-drug binding analysis through the measurements of electrophoretic mobilities. The utilisation of ILATPS has shown to have a positive impact on the stability of AGP activity solution during the storage for an extended period of time. In addition, the effect of various alkyl chains (C2-C10) of imidazolium-based ILs with concentrations ranging between 10.00 and 1000.0 μmol L⁻¹ on the AGP binding with the anti-cancer drugs chlorambucil (CHL) and dacarbazine (DAC) was examined by the system developed (ILATPS/ACE). A 100.00 μmol L⁻¹ 1-ethyl-3-methylimidazolium chloride (EMImCl) prepared in the physiological buffer conditions containing AGP (5.00–100.00 µmol L⁻¹) has provided an accurate apparent binding constant of 1.99 ± 0.11 and 6.95 ± 0.14 L mmol⁻¹ with CHL and DAC respectively. Apart from the ACE analysis, EMImCl/phosphate buffer solution was found to be a distinguished system that could lengthen the stability of AGP activity for a period of time reaching 90 days during the solution storage at 4.00 °C. This effect is thought to be due to the easy conversion of one-phase EMImCl/phosphate buffer/AGP at the ambient lab temperature into the two-phase solution at refrigerator temperature, 4.00 °C, and vice versa. Therefore, the ILATP/ACE system could be used to enhance the accuracy for other AGP-drug bindings with a fast, easy to use, and cost-effective analysis.     

Antibacterial activity of flavonoids and triterpenoids isolated from the stem bark and sap of Staudtia kamerunensis Warb. (Myristicaceae)

The chemical investigation of the ethyl acetate extract of the stem bark of Staudtia kamerunensis and sap led to the isolation of six compounds which included three isoflavonoids: biochanin A (1), formononetin (2) and 3-(1,3-benzodioxol-5-yl)-5,6,7-trimethoxy-4H-1-benzopyran-4-one (3), one flavonoid: (-) epicatechin (4) and two pentacyclic triterpenoids (oleanan-12-ene-2α,3β -diol (5) and 2α,3β-dihydroxylup-20-ene (6). They were characterized by HREIMS (High Resolution Electron Ionisation Mass Spectrometry), NMR spectroscopy (1D and 2D) and comparison with existing data in literature. The crude extract and isolates were tested against twelve bacterial strains namely; Bacillus subtilis, Staphylococcus epidermidis, Enterococcus faecalis, Mycobacterium smegmatis, Staphylococcus aureus, Enterobacter cloacae, Klebsiella oxytoca, Pseudomonas aeruginosa, Proteus vulgaris, Escherichia coli, Proteus mirabilis and Klebsiella pneumonia. Streptomycin, nalidixic acid and ampicillin were used as standard antibacterial drugs. The results revealed significant antibacterial activity for both the ethyl acetate partition and for the tested compounds, with the lowest MIC value being 15.625 μg/mL. A synergistic activity of the isolated triterpenoids was evaluated with interesting results. On a general note, the antibacterial activity of compound 5 was doubled specifically against Gram-negative bacterial strains. This could be a therapeutic antimicrobial pathway in face of the rising bacterial resistance. To the best of our knowledge, it is the first time that flavonoids and triterpenoids are isolated from this genus and species. It is also the first report of antibacterial studies on this species.     

Cyclometalated complexes containing ferrocenyl Schiff base: Preparation,characterization, DFT calculations,application in cancer and biological researches and MOE studies

A series of transition metal (II/III) complexes containing organometallic Schiff base ligand (H₂L) had been synthesized and characterized by using elemental analysis (C, H, N, M), molar conductivity, IR, UV–Vis, ¹H NMR and mass spectral analysis. Also, their TG and DTG behaviors were investigated. The ligand was prepared by condensation of 4-aminosalicylic acid with 2-acetylferrocene in 1:1 M ratio. The data of elemental analysis indicated that the prepared complexes were synthesized also in a 1:1 M ratio. The ligand behaved as neutral bidentate ligand that coordinated to metal ions through protonated O-phenolic and protonated carboxylic-OH groups. All complexes had octahedral structure. DFT calculations for H₂L ligand were determined with some parameters such as HOMO-LUMO energy gab, electronegativity and chemical hardness–softness. Antimicrobial activity of both H₂L Schiff base ligand and its metal complexes was tested against different strains of bacteria and fungi species. Furthermore, all compounds had been screened for their anticancer activities against breast cancer (MCF-7) cell line. [Cu(H₂L)(H₂O)₂Cl₂]·2H₂O complex had the lowest IC₅₀ value = 47.3 µg/mL. For determining the more effective and probable binding mode between the H₂L ligand, Co(II) and Zn(II) complexes with different active sites of 4K3V, 2YLB and 3DJD receptors, so molecular docking studies were investigated.     

Basic characterization and Alzheimer’s disease relieving property of a glucose riched polysaccharide from Cibotium barometz

The water-soluble polysaccharides from plants have attracted ever-increasing attention in the field of food and drug due to their various activities and low toxicity. CBP50-1, as a purified fraction of polysaccharide from the rhizome of Cibotium barometz (CBP), mainly consisted of glucose (55.45%) and xylose (25.27%). CBP50-1 showed excellent antioxidant activity for scavenging 2,2?Diphenyl?1?picryl?hydrazy (DPPH) radical and hydroxyl radical, further inhibiting lipid peroxidation. CBP50-1 significantly improved the survival rate of Caenorhabditis elegans under thermal and oxidative stress. Furthermore, CBP50-1 reduced the paralysis and oxidative damage induced by amyloid-beta (Aβ) and increased the antioxidant enzyme activity in Alzheimer’s disease (AD) model C. elegans CL4176 through c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) signal pathway. Thus, CBP50-1 had a potential application in health industries.     

Multi spectroscopic and computational investigations on the electronic structure of oxyclozanide

The present work contributes to a combined theoretical and experimental investigation on oxyclozanide. The experimental vibrational spectra were characterized by Fourier transform infrared (4000-400 cm^?1), Fourier transform Raman (4000-400 cm^?1), ¹H and ¹³C NMR were recorded in Deuterated methanol, UV–Vis (200–400 nm) techniques and theoretical optimized molecular geometry, harmonic vibrational spectra, magnetic spectra, and electronic spectra was calculated by Density Functional Theory (DFT) employed with B3LYP/6-311++G(d,p) basis set and compared with experimental data. The highest occupied molecular orbital - lowest unoccupied molecular orbital (HOMO-LUMO) energy was also calculated for the titled compound. The intermolecular interactions have been addressed through Hirshfeld surface analysis. In addition, Natural bond orbital (NBO) analyses of the title compound were performed to evaluate the suitable reactivity site and chemical stabilization behavior, Mulliken atomic charge distribution, and molecular electrostatic potential energy surfaces, were calculated to get a better insight into the structure of oxyclozanide. The experimental and theoretical findings suggest an excellent correlation to confirm the structure of oxyclozanide.     

Formulation and molecular docking simulation study of luliconazole nanosuspension–based nanogel for transdermal drug delivery using modified polymer

The purpose of study was to formulate nanosuspension-based nanogel of luliconazole (LLZ) for transdermal delivery to enhance its skin retention and effectiveness using modified starch ester. Nanosuspensions show promising results with size of 369.1–745.4 nm having PDI 0.193–0.344 and zeta potential 22–45 mV. These nanosuspensions form micelles and hydrophobic core of it provides the reservoir for LLZ with better drug loading and binding interaction. Drug loading was confirmed by percent drug entrapment efficiency (PDEE) and PDI. Molecular docking simulation (MDS) provides detail insight of LLZ polymer complexation at hydrophobic cavity of micelles and revealed that there was binding between drug and polymer in aqueous milieu having interaction energy ranges from ?7.1 to ?6.0 kcal/mol. Nanosuspensions so made were incorporated into gel by using Carbopol 934 ® and tested for % drug content, spreadability, pH, and viscosity with ranges of 101.62–97.71, 28.94–34.38 (gcm/s), 6.91–7.21, and 4802.62–9461.83 (cp), respectively. Nanogel also evaluated for stability and skin permeation study using human cadaver skin (HCS). In vitro skin permeation study indicated that the amount of LLZ permeated through skin from nanogel (71.042–83.818 μgcm ?2) was higher than standard cream (70.085 μgcm ?2). Nanogel increased the accumulation of LLZ in HCS ~3 times than standard cream. The transdermal flux was greater for standard cream (123.79 μgcm ?2), whereas smaller for nanogel (50.394–82.743 μgcm ?2) due to skin retention. Nanosuspension-based gel are able to especially favor LLZ accumulation into skin, provide better drug loading, improve stability, and efficacy. Thus, targeting older antibiotics such as LLZ and formulating into nanosystem utilized to expand its usefulness to physicians to treat illnesses caused by resistant fungal strains.     

Multi-component pharmacokinetics assessment of Artemisia annua L. in rats based on LC-ESI-MS/MS quantification combined with molecular docking

Artemisia annua L. (A. annua) has been used as herbal medicine in China for thousands of years for clearing deficiency heat, treating malaria and removing jaundice. A rapid, sensitive and specific liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC–ESI–MS/MS) method was developed, validated, and successfully used for simultaneous quantification of the active components in rat plasma after oral administration of A. annua extract. Molecular docking of each component with drug metabolizing enzymes was carried out to explore the effect of each component on CYP-mediated drug metabolism. Two coumarins (scopolin (SPL) and scopoletin (SPLT)), three flavonoids (rutin (RUT), chrysosplenol D (CHD), casticin (CAS)) and three sesquiterpenes (arteannuin B (ARN), dihydroartemisinic acid (DARM) and artemisinic acid (ARM)) were detected in rat plasma after oral administration. CHD and CAS were rapidly absorbed into rat blood with the T_max values of 0.11 ± 0.04 h and 0.13 ± 0.05 h, respectively. Their half-lives (t_1/2 2.68 ± 3.62 h and 0.33 ± 0.07 h) were shorter. SPLT were also rapidly absorbed into the blood (T_max 0.15 ± 0.03 h), but exhibited a longer half-life (t_1/2 6.53 ± 1.84 h), indicating that it could be effective in vivo for a longer period of time. The peak time of SPL, RUT, DARM and ARM ranged from 1 ～ 4 h, demonstrating that they could maintain considerable concentrations for a longer time. ARN showed strong enterohepatic circulation in rats, leading to slower onset time and longer effect. A few components including SPLT, CHD, CAS and ARN could be metabolized into their corresponding II phase metabolites combining with glucuronic acid or sulfuric acid. RUT could decompose its glycosyl to generate genin. The molecular docking results indicated that those flavonoids and coumarins of A. annua interacting with CYPs mainly through hydrogen bonding and π-π stacking had better CYP450 enzyme binding ability than the sesquiterpenoids, which were easier to induce drug interactions. This study presented an integrated strategy for investigating the pharmacokinetic behaviors of eight components in A. annua and laid the foundation for revealing the mechanism of action of A. annua in the organism.     

Nanoparticles: Properties,applications and toxicities

This review is provided a detailed overview of the synthesis, properties and applications of nanoparticles (NPs) exist in different forms. NPs are tiny materials having size ranges from 1 to 100 nm. They can be classified into different classes based on their properties, shapes or sizes. The different groups include fullerenes, metal NPs, ceramic NPs, and polymeric NPs. NPs possess unique physical and chemical properties due to their high surface area and nanoscale size. Their optical properties are reported to be dependent on the size, which imparts different colors due to absorption in the visible region. Their reactivity, toughness and other properties are also dependent on their unique size, shape and structure. Due to these characteristics, they are suitable candidates for various commercial and domestic applications, which include catalysis, imaging, medical applications, energy-based research, and environmental applications. Heavy metal NPs of lead, mercury and tin are reported to be so rigid and stable that their degradation is not easily achievable, which can lead to many environmental toxicities.     

Synthesis,pharmacological evaluation,and molecular modeling studies of novel isatin hybrids as potential anticancer agents

A novel series of isatin hybrids 5a-g was designed, synthesized, and characterized spectroscopically. The synthesized compounds were evaluated for their cytotoxic activity against the human breast cancer cell line (MCF-7) by in vitro MTT assay. Amongst the tested compounds, 5e compound bearing benzyl moiety at N₄ piperazine was found to be the most active with the promising IC₅₀ (12.47 µM). Moreover, the active compounds 5e and 5g were subjected to antitumor evaluation (in vivo) against Dalton’s ascitic lymphoma (DAL) cell line and the results suggested that the best active compound 5e can normalize the blood picture in comparison to the standard drug. An in silico molecular docking study using the crystal structure of Hsp90 protein described the role of significant protein–ligand interactions and revealed more insights into the binding mode. The drug-likeliness of the compounds was predicted based on Lipinski's rule of five and pharmacokinetic ADME parameters. Hence, the synthesized isatin hybrids could be novel starting point anticancer lead compounds demonstrating drug-like properties which can be explored further for anticancer drug discovery.     

Bioanalytical method validation,biopharmaceutical and pharmacokinetic evaluation of GSK-650394, a serum- and glucocorticoid-regulated kinase 1 inhibitor

GSK-650394 is an inhibitor of serum- and glucocorticoid-regulated kinase 1 that displays potency for treating cancer, hypertension, cardiovascular and neuronal diseases, such as Parkinson’s disease. However, the biopharmaceutical properties and pharmacokinetics of GSK-650394 have not been studied extensively. Also, there are currently no bioanalytical assays available for this new drug candidate. In this study, we developed a simple and sensitive liquid chromatography-tandem mass spectrometry method to quantify GSK-650394 in rat plasma and validated its selectivity, linearity, accuracy and precision, sensitivity, matrix effects, extraction recovery, and stability, following the United States Food and Drug Administration guidelines. In vitro studies showed the biopharmaceutical properties of GSK-650394, including its low solubility in water and simulated gastrointestinal fluids, passive transport in Caco-2 cell monolayers, high plasma protein binding, and primary metabolism by glucuronide conjugation in the small intestine and liver of rats. Following intravenous administration (2 mg/kg) to rats, GSK-650394 exhibited low total clearance (11.18 ± 1.28 mL/min/kg) and volume of distribution at steady-state (346.1 ± 120.6 mL/kg). Following oral administration (2, 5, and 10 mg/kg) to rats, GSK-650394 underwent enterohepatic circulation, with low bioavailability (～9%). The insignificant difference in bioavailability among three oral doses suggests that GSK-650394 may follow linear pharmacokinetics up to an oral dose of 10 mg/kg. In addition, the total form of parent drug and glucuronide conjugate in rat plasma from three oral doses showed a much higher value of area under the plasma concentration versus time curve than the parent drug, indicating that the primary metabolism process of GSK-650394 was glucuronidation. Our findings suggest that the low oral bioavailability of GSK-650394 is associated with its low solubility, instability under acidic gastric conditions, and extensive glucuronidation metabolism.     

Pharmacophore model-aided virtual screening combined with comparative molecular docking and molecular dynamics for identification of marine natural products as SARS-CoV-2 papain-like protease inhibitors

Targeting SARS-CoV-2 papain-like protease using inhibitors is a suitable approach for inhibition of virus replication and dysregulation of host anti-viral immunity. Engaging all five binding sites far from the catalytic site of PLpro is essential for developing a potent inhibitor. We developed and validated a structure-based pharmacophore model with 9 features of a potent PLpro inhibitor. The pharmacophore model-aided virtual screening of the comprehensive marine natural product database predicted 66 initial hits. This hit library was downsized by filtration through a molecular weight filter of ≤ 500 g/mol. The 50 resultant hits were screened by comparative molecular docking using AutoDock and AutoDock Vina. Comparative molecular docking enables benchmarking docking and relieves the disparities in the search and scoring functions of docking engines. Both docking engines retrieved 3 same compounds at different positions in the top 1 % rank, hence consensus scoring was applied, through which CMNPD28766, aspergillipeptide F emerged as the best PLpro inhibitor. Aspergillipeptide F topped the 50-hit library with a pharmacophore-fit score of 75.916. Favorable binding interactions were predicted between aspergillipeptide F and PLpro similar to the native ligand XR8-24. Aspergillipeptide F was able to engage all the 5 binding sites including the newly discovered BL2 groove, site V. Molecular dynamics for quantification of Cα-atom movements of PLpro after ligand binding indicated that it exhibits highly correlated domain movements contributing to the low free energy of binding and a stable conformation. Thus, aspergillipeptide F is a promising candidate for pharmaceutical and clinical development as a potent SARS-CoV-2 PLpro inhibitor.     

Synthesis,characterization, and application of griseofulvin surface molecularly imprinted polymers as the selective solid phase extraction sorbent in rat plasma samples

In present study, an investigation was carried out to develop and validate an analytical method for the selective extraction and determination of griseofulvin (GSF) from plasma samples. For this purpose, a rational approach was made to synthesize and characterize the surface molecularly imprinted polymers (SMIPs). The SMIPs were utilized as solid phase extraction (SPE) sorbents. The SMIPs were prepared by using GSF as template molecule on the surface of modified silica particles through a non-covalent technique. The particles demonstrated high adsorption capacity (119.1 µg/mL), fast adsorption equilibrium time (30 min) and good recognition selectivity for the template drug. The scanning electron microscopy and infrared spectroscopy were used to explain the structural and morphological characteristics of the SMIPs and surface non-imprinted polymers. The SPE method was combined with HPLC for plasma analysis. The method validation results demonstrated that the established method possessed good linearity for GSF ranging from 0.1 to 50 µg/mL (R² = 0.997). The limit of detection for this method was 0.02 µg/mL for rat plasma samples. The recoveries of GSF from spiked plasma samples were (90.7–97.7%) and relative standard deviations were (0.9–4.5%). Moreover, the SMIPs as selective SPE sorbent can be reused more than 8 times which is a clear advantage over commercial SPE sorbents. Finally, the usefulness of the proposed strategy was assessed by extraction and detection of GSF in real rat plasma samples.