Design and synthesis of pyrazolone-based compounds as potent blockers of SARS-CoV-2 viral entry into the host cells

SARS-CoV-2 are enveloped positive-stranded RNA viruses that replicate in the cytoplasm. It relies on the fusion of their envelope with the host cell membrane to deliver their nucleocapsid into the host cell. The spike glycoprotein (S) mediates virus entry into cells via the human Angiotensin-converting enzyme 2 (hACE2) protein located on many cell types and tissues' outer surface. This study, therefore, aimed to design and synthesize novel pyrazolone-based compounds as potential inhibitors that would interrupt the interaction between the viral spike protein and the host cell receptor to prevent SARS-CoV 2 entrance into the cell. A series of pyrazolone compounds as potential SARS-CoV-2 inhibitors were designed and synthesized. Employing computational techniques, the inhibitory potentials of the designed compounds against both spike protein and hACE2 were evaluated. Results of the binding free energy from the in-silico analysis, showed that three compounds (7i, 7k and 8f) and six compounds (7b, 7h, 7k, 8d, 8g, and 8h) showed higher and better binding high affinity to SARS-CoV-2 Sgp and hACE-2, respectively compared to the standard drugs cefoperazone (CFZ) and MLN-4760. Furthermore, the outcome of the structural analysis of the two proteins upon binding of the inhibitors showed that the two proteins (SARS-CoV-2 Sgp and hACE-2) were stable, and the structural integrity of the proteins was not compromised. This study suggests pyrazolone-based compounds might be potent blockers of the viral entry into the host cells.

Antidiabetes and antioxidant potential of Schiff bases derived from 2-naphthaldehye and substituted aromatic amines: Synthesis, crystal structure, Hirshfeld surface analysis, computational, and invitro studies

Three Schiff bases were synthesised by the condensation reaction between 2-napthaldehyde and aromatic amines to afford (E)-N-mesityl-1-(naphthalen-2-yl)methanimine (L1), (E)-N-(2,6-dimethylphenyl)-1-(naphthalen-2-yl)methanimine (L2) and (E)-N-(2,6-diisopropylphenyl)-1-(naphthalen-2-yl)methanimine (L3). The synthesised compounds were characterised using UV-visible, NMR (13C & 1H), and Fourier transform infrared spectroscopic methods while their purity was ascertained by elemental analysis. Structural analysis revealed that the naphthalene ring is almost coplanar with the imine functional group as evident by C1-C10-C11-N1 torsion angles of 176.4(2)° and 179.4(1)° in L2 and L3, respectively. Of all the various intermolecular contacts, H⋯H interactions contributed mostly towards the Hirshfeld surfaces of both L2 (58.7 %) and L3 (69.7 %). Quantum chemical descriptors of L1 - L3 were determined using Density Functional Theory (DFT) and the results obtained showed that the energy band gap (ΔE) for L1, L2 and L3 are 3.872, 4.023 and 4.004 eV respectively. The antidiabetic potential of the three compounds were studied using α-amylase and α-glucosidase assay. Compound L1 showed very promising antidiabetic activities with IC50 values of 58.85 μg/mL and 57.60 μg/mL while the reference drug (Acarbose) had 405.84 μg/mL and 35.69 μg/mL for α-amylase and α-glucosidase respectively. In-silico studies showed that L1 docking score as well as binding energies are higher than that of acarbose, which are recognized inhibitors of α-amylase together with α-glucosidase. Further insight from the RMSF, RMSD and RoG analysis predicted that, throughout the simulation L1 showcased evident influence on the structural stability of α-amylase. The antioxidant potential of the compounds was carried out using nitric oxide (NO), ferric reducing ability power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. The compounds exhibited good to fairly antioxidant properties with L1 as well as L3 having IC50 values of 70.91 and 91.21 μg/mL respectively for NO scavenging activities assay, which comparatively outshined acarbose (reference drug) with IC50 value of 109.95 μg/mL. Pharmacology and pharmacokinetics approximations of L1 - L3 showed minimal violation of Lipinski's Ro5 and this projects them to be less toxic and orally bioavailable as potential templates for the design of therapeutics with antioxidant and antidiabetic activities.

Development of niosomes for encapsulating captopril-quercetin prodrug to combat hypertension

Novel and effective anti-hypertensive agents are required to manage hypertension; therefore, we synthesised a novel antihypertensive drug from captopril and quercetin (cap-que) and explored its antihypertensive potential in a niosomal formulation via molecular hybridisation. The cap-que hybrid was synthesised, and its structure was characterised via NMR, FTIR, and HRMS. Niosomes were then loaded with cap-que using the thin-film hydration method. The particle size, polydispersity index, surface charge and drug entrapment efficiency (EE%) of the formulation were 418.8 ± 4.21 nm, 0.393 ± 0.063, 16.25 ± 0.21 mV, and 87.74 ± 2.82%, respectively. The drug release profile showed a sustained release of the active compound (43 ± 0.09%) from the niosomal formulation, compared to the parent drug (80.7 ± 4.68%), over 24 h. The cell viability study confirmed the biosafety of the formulation. The in vivo study in a rat model showed enhanced antihypertensive activity of the hybrid molecule and niosomal formulation which reduced systolic and diastolic pressure when compared to the individual, bare drugs. The findings of this study concluded that the antihypertensive potential of captopril can be enhanced by its hybridisation with quercetin, followed by niosomal nano drug delivery.

Exploring the therapeutic potential of prolinamides as multi-targeted agents for Alzheimer's disease treatment: molecular docking and molecular dynamic simulation studies

Alzheimer's disease (AD) presents a significant global health challenge, with its prevalence expected to rise sharply in the coming years. Despite extensive research, effective treatments addressing the multifaceted pathophysiology of AD remain elusive. This study investigates the therapeutic potential of twenty-seven prolinamides (P1 - P27), with the focus on their interactions with key proteins implicated in AD pathogenesis. Four of the compounds, namely; 10-((4-nitrophenyl)prolyl)-10 H-phenothiazine (P14), 2-((4-nitrophenyl)prolyl)isoindoline (P19), 1-(4-formylphenyl)-N-(p-tolyl)pyrrolidine-2-carboxamide (P22), and N,1-bis(4-nitrophenyl)pyrrolidine-2-carboxamide (P27) showed promising potential as Alzheimer's drug. In-silico approaches including molecular docking, molecular dynamic (MD) simulation, post md study, physicochemical and drug-likeness parameters were employed to ascertain the potential of these compounds as inhibitors of certain proteins implicated in the pathophysiology of Alzheimer's disease. Molecular docking and dynamics simulations demonstrated that P14, P19, P22 and P27 exhibited promising binding affinities towards crucial AD-associated proteins, including Beta-Secretase 1 (BACE1), Butyrylcholinesterase (BuChE), and Tau-tubulin kinase 2 (TTBK2). Structural stability analyses revealed that prolinamides, particularly P22 and P27 for BACE1 and P14 and P19 for BuChE, exhibited greater stability than their reference ligands, indicated by lower RMSD, RoG, and RMSF values. For BuChE, Rivastigmine had a docking score of -7.0 kcal/mol, a binding free energy (ΔGbind) of -22.19 ± 2.44 kcal/mol, RMSD of 1.361 ± 0.162 Å, RMSF of 9.357 ± 3.212 Å, and RoG of 22.919 ± 0.064 Å, whereas P19 exhibited a superior docking score of -10.3 kcal/mol, a significantly better ΔGbind of -33.74 ± 2.84 kcal/mol, RMSD of 1.347 ± 0.132 Å, RMSF of 8.164 ± 2.748 Å, and RoG of 22.868 ± 0.070 Å. Physicochemical and pharmacokinetic assessments affirmed the drug-likeness and bioavailability of P19 notably capable of penetrating the blood-brain barrier. Compounds P19 and P22, emerged as multi-targeted ligands, offering the potential for simultaneous modulation of multiple AD-related pathways. These findings highlight the possibilities of these compounds to be explored as novel therapeutic agents for AD. They also highlight the need for further experimental validation to confirm their efficacy and safety profiles, advancing them toward clinical application in AD management.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-024-00250-z.

Design and Evaluation of Quinoline-Schiff Bases Targeting Mtb DNA Gyrase: In Vitro and Computational Approaches

A new series of quinoline-Schiff bases was designed and synthesized using a straightforward and efficient methodology involving the condensation of 2-chloroquinoline-3-carbaldehyde with substituted aromatic amines. A total of 17 quinoline-Schiff bases were synthesized with 56%-86% yields and characterized by using 1H NMR, 13C NMR, and high-resolution mass spectra (HRMS) as potent anti-mycobacterial agents with Mtb DNA gyrase inhibitory activity. Among all, compound 7f displayed a significantly potent broad-spectrum antitubercular and antimicrobial activity against most of the tested strains of bacteria and fungi, with minimum inhibitory concentration (MIC) values in the range of 1.95-15.62 µg/mL. Seven quinoline-Schiff bases (7a, 7b, 7d, 7g, 7o, 7p, and 7q) displayed a key improvement in both drug-sensitive and drug-resistant strains with MIC range of 3.90-15.62 µg/mL, respectively. A subsequent in vitro study evaluated the most promising compounds (7a, 7d, 7f, 7p, and 7q) against Mtb DNA gyrase. Among these, compounds 7a, 7d, and 7f exhibited the highest activity, with IC50 values of 1.98, 1.26, and 3.96 µM, respectively. Molecular docking studies revealed strong binding affinities of the synthesized derivatives with the Mtb DNA gyrase enzyme, highlighting key hydrogen and carbon-hydrogen bond interactions with Tyr21, Gly84, Asn85, Asp110, Gln125, and pi-pi and pi-alkyl interactions with Arg62, Phe116, Pro118, Ala146, and Val147. Furthermore, ADMET profiling of the most effective derivatives 7a, 7d, and 7f demonstrated comparable bioavailability scores (0.55) with varied lipophilicity (MLOGP: 2.90-3.39) and lower TPSA compared to ciprofloxacin (CFX). These comprehensive analyses and properties suggest favorable drug-likeness with potential for further optimization.

A promising class of antiprotozoal agents, design and synthesis of novel Pyrimidine-Cinnamoyl hybrids

Malaria, caused by parasitic protozoans of the Plasmodium genus, continues to be one of the greatest global health crises, especially in Africa. The emergence of antimalarial drug resistance continues to be a health problem necessitating an urgent need for alternative and cost-effective antimalarials. Using a molecular hybridization approach, we report the design and synthesis of an efficacious novel class of antiprotozoal agents; (E)-1-(4-(4,6-diphenylpyrimidin-2-yl)piperazin-1-yl)-3-phenyl prop-2-en-1-one derivatives (8a-r). The in vitro inhibitory activity of the synthesized compounds was evaluated against the NF54 chloroquine-sensitive strain of Plasmodium falciparum. From the antiprotozoal screening, three compounds displayed propitious activity with IC50 values (0.18-0.21 μM), using quinine and chloroquine as standard antimalarials. Compounds 8o and 8l emerged as the most potent candidates with IC50 values of 0.18 ± 0.02 μM and 0.21 ± 0.001 μM with an associated good safety index of 18.59 and 16.75 to human kidney epithelial (HEK293) cells, respectively. The synthesized analogues present a new chemical architecture structurally unrelated to the current regime of antimalarial drugs, representing a valid strategy to combat resistance in P. falciparum species to current commercial drugs. We further investigated the binding affinities of the compounds against recombinant forms of two P. falciparum heat shock protein 70 homologues; PfHsp70-1 and PfHsp70-z, both of which are essential and promising druggable candidates. Compound 8l exhibited the highest binding affinity for PfHsp70-1 and PfHsp70-z. Furthermore, molecular docking revealed that compounds 8k, 8l, 8m, and 8o exhibited better fitness to PfHsp70-1, with compounds 8l and 8o showing the highest binding affinity of -10.5 kcal/mol and -10.1 kcal/mol, respectively. Therefore, it can be speculated that PfHsp70-1 may be a possible target of some of the inhibitors tested in this study. The presence of electron-donating groups on the phenyl ring of 4,6-pyrimidine moiety and cinnamoyl group demonstrated a positive correlation between the observed computational data and the biological activity. Taken together, this paper demonstrates the importance of using the molecular hybridization approach in the development of newer cinnamoyl clubbed with 4,6-diphenyl pyrimidine hybrids as potential antiprotozoal agents.

In silico exploration of natural xanthone derivatives as potential inhibitors of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication and cellular entry

The COVID-19 pandemic, caused by SARS-CoV-2, has underscored the urgent need for effective antiviral therapies, particularly against vaccine-resistant variants. This study investigates natural xanthone derivatives as potential inhibitors of the ACE2 receptor, a critical entry point for the virus. We computationally evaluated 91 xanthone compounds derived from Swertia chirayita, identifying two promising candidates: 8-O-[β-D-Xylopyranosyl-(1→6)-β-D-glucopyranosyl]-1,7-dihydroxy-3-methoxy xanthone (XAN71) and 8-O-[β-D-Xylopyranosyl-(1→6)-β-D-glucopyranosyl]-1-hydroxy-3,7-dimethoxy-xanthone (XAN72). Molecular docking and dynamics simulations (MDDS) were performed to assess their binding energy and stability within the ACE2 active site, comparing them to the reference inhibitor MLN-4067. The top six compounds were selected based on their docking performance, followed by Molecular Mechanics/Poisson-Boltzmann Surface Area (MM/PBSA) calculations to quantify binding affinities. Additionally, molecular electrostatic potential (MEP) analysis was conducted to visualize electron density regions relevant to binding interactions. Our results demonstrate that XAN71 and XAN72 exhibit superior binding affinities of -70.97 and - 69.85 kcal/mol, respectively, outperforming MLN-4067 (-61.33 kcal/mol). MD simulations revealed stable interactions with key ACE2 residues, primarily through hydrogen bonds and hydrophobic contacts. The Molecular Electrostatic Potential(MEP) analysis further elucidated critical electron density regions that enhance binding stability. This study establishes XAN71 and XAN72 as viable candidates for ACE2 inhibition, providing a structural basis for their development as natural xanthone-based therapeutics against SARS-CoV-2. These findings highlight the potential of targeting ACE2 with natural compounds to combat COVID-19, particularly in light of emerging viral variants.

Assessing the efficacy of iso-mukaadial acetate and betulinic acid against selected Plasmodium falciparum glycolytic pathway proteins: in silico and in vitro studies

Malaria is the extensive health concern in sub-Saharan Africa, with Plasmodium falciparum being the most lethal strain. The continued emergence of drug-resistant P. falciparum advocates for the development of new antimalarials. Our current study aimed to effectively explore the interaction capabilities of iso-mukaadial acetate (IMA) and betulinic acid (BA) against two essential P. falciparum glycolytic pathway proteins, PfLDH and PfHk. Recombinant PfLDH and PfHk were independently expressed in E. coli BL21 (DE3) cells and subsequently purified using affinity chromatography. Protein-ligand interaction studies probed in silico and in vitro approaches. Parasite inhibition studies confirmed potent antimalarial activity against the P. falciparum NF54 strains, with BA and IMA showing IC50 values of 1.27 µg/ml and 1.03 µg/ml against the asexual stage of P. falciparum, respectively. FTIR experiments confirmed interactions between the compounds and the secondary structure of the proteins. Direct protein-ligand interaction studies analysis using microscale thermophoresis (MST) showed a KD value of 0.1036 ± 0.6001 µM for the PfLDH-BA complex and 0.7473 ± 0.3554 µM KD value for PfLDH-IMA. Meanwhile, PfHk-IMA had 0.39701 ± 0.16298 µM KD value, while the PfHk-BA complex had no interaction detected. Molecular docking and molecular dynamics simulation studies were used to measure and confirm the interactive strength of complexes. Molecular docking reported a binding score of - 1.155 kcal/mol for the PfLDH-BA complex and a binding score of - 3.200 kcal/mol for PfLDH-IMA. The PfHk-BA complex had - 2.871 kcal/mol and PfHk-IMA complex had - 4.225 kcal/mol binding score. In conclusion, BA and IMA compounds had better interactions and remained bound within the binding sites of the glycolytic pathway proteins (PfLDH and PfHk).