Design, Synthesis, and Antimicrobial Evaluation of a New Series of N-Sulfonamide 2-Pyridones as Dual Inhibitors of DHPS and DHFR Enzymes

Design, Synthesis, DFT, docking Studies, and antimicrobial evaluation of novel benzimidazole containing sulphonamide derivatives

In silico approaches have been employed to design a new series of benzimidazole-containing sulphonamide derivatives and qualified compounds have been synthesized to analyze their potential as antimicrobial agents. Antibacterial screening of all synthesized compounds was done using the broth microdilution method against several human pathogenic bacteria, viz. Gram-positive bacteria [B. cerus (NCIN-2156), B. subtilis (ATCC-6051), S. aureus (NCIM-2079)] and Gram-negative bacteria [P. aeruginosa (NCIM-2036), E. coli (NCIM-2065), and a drug-resistant strain of E. coli (U-621)], and the compounds presented admirable MIC values, ranging between 100-1.56 µg/mL. The combinatorial analysis showed the magnificent inhibitory efficiency of the tested compounds, acquired equipotent to ten-fold more potency compared to original MIC values. An immense synergistic effect was exhibited by the compounds during combination studies with reference drugs chloramphenicol and sulfamethoxazole was presented as fractional inhibitory concentration (∑FIC). Enzyme inhibition studies of all synthesized compounds were done by using peptidyl transferase and dihydropteroate synthase enzymes isolated from E. coli and S. aureus and each of the compound presented the admirable IC50 values, where the lead compound 3 bound to peptidyl transferase (of S. aureus with IC50 363.51 ± 2.54 µM and E. coli IC50 1.04 ± 0.08 µM) & dihydropteroate synthase (of S. aureus IC50 3.51 ± 0.82 µM and E. coli IC50 2.77 ± 0.65 µM), might account for the antimicrobial effect, exhibited excellent inhibition potential. Antifungal screening was also performed employing food poisoning methods against several pathogenic fungal species, viz A. flavus, F. oxysporum, A. niger, and A. brassicae. The obtained result indicated that few compounds can prove to be a potent drug regimen against dreaded MDR strains of microbes. Structural activity relationship (SAR) analysis and docking studies reveal that the presence of electron-withdrawing, polar, and more lipophilic substituents positively favor the antibacterial activity, whereas, electron-withdrawing, more polar, and hydrophilic substituents favor the antifungal activities. A robust coherence has been found in in-silico and in-vitro biological screening results of the compounds.

Phthalazine Sulfonamide Derivatives as Carbonic Anhydrase Inhibitors. Synthesis, Biological and in silico Evaluation

Carbonic Anhydrases (CAs) are a large family of zinc metalloenzymes that catalyze the reversible hydration of carbon dioxide involved in several biological processes. They show a wide diversity in tissue distribution and their subcellular localization. Twenty-two novel phthalazine derivatives were designed, synthesized, and evaluated against four human isoforms: hCA I, hCA II, hCA IX, and hCA XII. Compounds appeared to be very active mostly against hCA IX (7) and hCA I (6) isoforms being more potent than reference drug acetazolamide (AAZ). Some compounds appeared to be very selective with a selectivity index up to 13.8. Furthermore, docking was performed for some of these compounds on all isoforms to understand the possible interactions with the active site. Additionally, the most active compounds against hCA IX were subjected to cell viability assay. The anticancer activity of the compounds (3 a-d, 5 d, 5 i, and 5 m) was investigated using two human breast cancer cell lines, i. e. MCF-7 and MDA-MB-231 cells, and the normal counterpart, namely MCF10-A cells.

Hybrid Caffeic Acid-Based DHFR Inhibitors as Novel Antimicrobial and Anticancer Agents

A novel series of 1,2,4-triazole analogues of caffeic acid was designed, synthesized, characterized, and assessed for their capacity to inhibit DHFR, as well as their anticancer and antimicrobial properties. A molecular docking analysis was conducted on DHFR, utilizing PDB IDs 1U72 and 2W9S, aiming to design anticancer and antimicrobial drugs, respectively. Among all the synthesized derivatives, compound CTh7 demonstrated the highest potency as a DHFR inhibitor, with an IC50 value of 0.15 μM. Additionally, it exhibited significant cytotoxic properties, with an IC50 value of 8.53 µM. The molecular docking analysis of the CTh7 compound revealed that it forms strong interactions with key residues of homo sapiens DHFR such as Glu30, Phe34, Tyr121, Ile16, Val115, and Phe31 within the target protein binding site and displayed excellent docking scores and binding energy (-9.9; -70.38 kcal/mol). Additionally, synthesized compounds were screened for antimicrobial properties, revealing significant antimicrobial potential against bacterial strains and moderate effects against fungal strains. Specifically, compound CTh3 exhibited notable antibacterial efficacy against Staphylococcus aureus (MIC = 5 µM). Similarly, compound CTh4 demonstrated significant antibacterial activity against both Escherichia coli and Pseudomonas aeruginosa, with MIC values of 5 µM for each. A docking analysis of the most active antimicrobial compound CTh3 revealed that it forms hydrogen bonds with Thr121 and Asn18, a π-cation bond with Phe92, and a salt bridge with the polar residue Asp27.

Novel Glu-based pyrazolo[3,4-d]pyrimidine analogues: design, synthesis and biological evaluation as DHFR and TS dual inhibitors

A novel series of multifunctional pyrazolo[3,4-d]pyrimidine-based glutamate analogs (6a-l and 7a,b) have been designed and synthesized as antifolate anticancer agents. Among the tested compounds, 6i exhibited the most potent anti-proliferative activity towards NSCLC, CNS, Ovarian, Prostate, Colon, Melanoma, Breast, and Renal cancers with good to weak cytostatic activity and non-lethal actions. 6i demonstrated higher selectivity for cancer than normal cells. 6i could significantly increase the accumulation of S-phase cells during the cell cycle distribution of cancer cells with high potency in the induction of apoptosis. The results unveiled that 6i probably acts through dual inhibition of DHFR and TS enzymes (IC₅₀ = 2.41 and 8.88 µM, correspondingly). Docking studies of 6i displayed that N1-p-bromophenyl and C3-Methyl groups participate in substantial hydrophobic interactions. The drug-likeness features inferred that 6i met the acceptance criteria of Pfizer. Taking together, 6i could be a promising prototype for further optimization as an effective anticancer drug.

Synthesis and Biological Evaluation of Benzothiazolyl-pyridine Hybrids as New Antiviral Agents against H5N1 Bird Flu and SARS-COV-2 Viruses

A novel series of benzothiazolyl-pyridine hybrids 8a-h and 14a-e were produced from the reaction of enamine derivative 4 with each of the arylcyanoacetamides 5a-h and cyanoacetohydrazides 9a-e. The new products were characterized by spectral techniques (IR, 1H NMR, 13C NMR, and MS). Biological evaluation of 8a-h and 14a-e in vitro against H5N1 and SARS-COV-2 viruses showed that several compounds had significant activity. Compounds 8f-h, which contain fluorine atoms, have better activity against H5N1 and anti-SARS-CoV-2 viruses than the other compounds included in this study. Compound 8h has a trifluoromethyl group at position-3 of the phenyl ring and exhibits a high activity against H5N1 virus with 93 and 60% inhibition at concentrations of 0.5 and 0.25 μmol/μL, respectively, among the tested compounds, and it also showed anti-SARS-CoV-2 virus with a half-maximum inhibition rate of 3.669 μM, among the remaining compounds. The mechanism of action of 8f-h, which is expected to be repurposed against COVID-19, was investigated. The results showed that the compounds have virucidal effects at different stages of the three mechanisms of action. Furthermore, compounds 8f-h were found to possess CoV-3CL protease inhibitory activities with IC50 values of 544.6, 868.2, and 240.6 μg/mL, respectively, compared to IC50 = 129.8 μg/mL of the standard drug lopinavir. Interestingly, compounds 8f-h also showed high inhibitory activity against the H5N1 virus as well as the SARS-CoV-2 virus. Moreover, compounds 8f-h fit admirably into the active site of the SARS-CoV-2 main protease (PDB ID: 6LU7) using the molecular docking Moe software 2015.10.

Synthesis, characterization, molecular docking, and antimicrobial activities of dinuclear nickel(ii), palladium(ii), and platinum(iv) complexes

New nickel(ii), palladium(ii), and platinum(iv) complexes were synthesized by reacting the metal ions with benzidinedioxime in a 1 : 1 mole ratio. The CHN elemental analysis, spectroscopic analyses, and powder X-ray diffraction (PXRD) results showed that two Ni(ii) and two Pd(ii) ions coordinated to two benzidinedioxime ligands via the nitrogen atoms of both oxime groups and the two azomethine nitrogen atoms. In the case of the dinuclear platinum(iv) complex, however, each Pt(iv) is coordinated with the two oxygen atoms of the oxime group and the two azomethine nitrogen atoms of the ligand. Both elemental analyses and PXRD indicated that the complex ions of Ni(ii) and Pt(iv) have distorted octahedral geometry, whereas Pd(ii) has a square planar geometry. Molecular docking studies showed that the nickel(ii) complex is the most potent dual DHPS/DHFR bacterial inhibitor. The receptor of the DHPS enzyme (3ZTE) showed the best interaction with the nickel(ii) complex when compared to a receptor of the DHFR enzyme (3FRB). All the synthesized complexes and ligand exhibited significant results against PS. Aeruginous than their corresponding SMX-TMP drug. Among the three synthesized complexes, the nickel(ii) complex possessed the highest antimicrobial activities against tested microorganisms.

N-Acylsulfonamide: a valuable moiety to design new sulfa drug analogues

Sulfonamides are the oldest class of antibiotics, discovered more than 80 years ago. They are still used today despite the appearance of drug resistance phenomena that limit their prescription. Since the discovery and use of the first sulfa drugs, many analogues have been synthesized in order to obtain new active molecules able to circumvent bacterial resistance. Structurally similar to sulfonamide, the N-acylsulfonamide group arouses interest in the field of medicinal chemistry due to specific physico-chemical properties. We report here the synthesis and antibacterial/antibiofilm activities of 18 sulfa drug analogues with an N-acylsulfonamide moiety. These derivatives were obtained efficiently by sulfo-click reactions between readily available thioacid and sulfonyl azide synthons.

Molecular mechanism of plasmid-borne resistance to sulfonamide antibiotics

The sulfonamides (sulfas) are the oldest class of antibacterial drugs and inhibit the bacterial dihydropteroate synthase (DHPS, encoded by folP), through chemical mimicry of its co-substrate p-aminobenzoic acid (pABA). Resistance to sulfa drugs is mediated either by mutations in folP or acquisition of sul genes, which code for sulfa-insensitive, divergent DHPS enzymes. While the molecular basis of resistance through folP mutations is well understood, the mechanisms mediating sul-based resistance have not been investigated in detail. Here, we determine crystal structures of the most common Sul enzyme types (Sul1, Sul2 and Sul3) in multiple ligand-bound states, revealing a substantial reorganization of their pABA-interaction region relative to the corresponding region of DHPS. We use biochemical and biophysical assays, mutational analysis, and in trans complementation of E. coli ΔfolP to show that a Phe-Gly sequence enables the Sul enzymes to discriminate against sulfas while retaining pABA binding and is necessary for broad resistance to sulfonamides. Experimental evolution of E. coli results in a strain harboring a sulfa-resistant DHPS variant that carries a Phe-Gly insertion in its active site, recapitulating this molecular mechanism. We also show that Sul enzymes possess increased active site conformational dynamics relative to DHPS, which could contribute to substrate discrimination. Our results reveal the molecular foundation for Sul-mediated drug resistance and facilitate the potential development of new sulfas less prone to resistance.

Novel Fluorescent Benzothiazolyl-Coumarin Hybrids as Anti-SARS-COVID-2 Agents Supported by Molecular Docking Studies: Design, Synthesis, X-ray Crystal Structures, DFT, and TD-DFT/PCM Calculations

This study revealed the design and preparation of new 3-(benzo[d]thiazol-2-yl)-2H-chromen-2-one derivatives 9a-h. The structures of the synthesized products were elucidated by their spectroscopic data and X-ray crystallography for compounds 9a and 9d. The prepared new compounds were measured for their fluorescence, and a good result indicated that the emission efficiency was decreased by increasing the electron-withdrawing groups from the unsubstituted compound 9a to the highly substituted derivative 9h (2 Br heavy atoms). On the other hand, the B3LYP/6-311G** theoretical level of theory was used to optimize the quantum mechanical calculations of the geometrical characteristics and energy of the novel compounds 9a-h under study. The electronic transition was investigated using the TD-DFT/PCM B3LYP approach, which uses time-dependent density functional calculations. Moreover, the compounds exhibited nonlinear optical properties (NLO) and a small HOMO-LUMO energy gap, which makes them easy to polarize. Furthermore, the acquired infrared spectra were compared with the expected harmonic vibrations of the substances 9a-h. On the other hand, binding energy analyses of compounds 9a-h with human corona virus nucleocapsid protein Nl63 (PDB ID: 5epw) were predicted using molecular docking and virtual screening tools. The results showed a promising binding and how these potent compounds were inhibiting the COVID-19 virus. Compound 9h was the most active anti-COVID-19 agent among all the synthesized benzothiazolyl-coumarin derivatives, as it forms five bonds. The presence of the two bromine atoms in its structure was responsible for the potent activity.

Acrylonitrile adducts: design, synthesis and biological evaluation as antimicrobial, haemolytic and thrombolytic agent

In this work, five acrylonitrile adducts were screened for antibacterial activity against Gram-positive Bacillus subtilis, Microbial Type Culture Collection and Gene Bank (MTCC 1305) and Gram-negative Escherichia coli (MTCC 443). Synthesis was followed by aza-Michael addition reaction, where the acrylonitrile accepts an electron pair from the respective amines and results in the formation of n-alkyliminobis-propionitrile and n-alkyliminopropionitrile under microwave irradiation. Characterization of the compounds were performed using Fourier Transform Infrared (FTIR), Proton Nuclear Magnetic Resonance (¹H NMR) and Electrospray Ionisation Mass Spectrometry (ESI-MS). The particle size characterization was done by Dynamic Light Scattering (DLS) technique. The antibacterial study showed higher inhibition rate for both Gram-positive and Gram-negative bacteria. The antibacterial ability was found to be dose dependent. The minimum inhibitory concentration against both bacteria were found to be 1, 3, 0.4, 1, 3 µl/ml for E. coli and 6, 6, 0.9, 0.5, 5 µl/ml for B. subtilis. Time-kill kinetics evaluation showed that the adducts possess bacteriostatic action. Further it was evaluated for high-throughput in vitro assays to determine the compatibility of the adducts for drug delivery. The haemolytic and thrombolytic activity was analysed against normal mouse erythrocytes. The haemolytic activity showed prominent results, and thereby projecting this acrylonitrile adducts as potent antimicrobial and haemolytic agent.

Synthesis, Biological and In Silico Studies of Griseofulvin and Usnic Acid Sulfonamide Derivatives as Fungal, Bacterial and Human Carbonic Anhydrase Inhibitors

Carbonic anhydrases (CAs, EC 4.2.1.1) catalyze the essential reaction of CO₂ hydration in all living organisms, being actively involved in the regulation of a plethora of patho-/physiological conditions. A series of griseofulvin and usnic acid sulfonamides were synthesized and tested as possible CA inhibitors. Since β- and γ- classes are expressed in microorganisms in addition to the α- class, showing substantial structural differences to the human isoforms they are also interesting as new antiinfective targets with a different mechanism of action for fighting the emerging problem of extensive drug resistance afflicting most countries worldwide. Griseofulvin and usnic acid sulfonamides were synthesized using methods of organic chemistry. Their inhibitory activity, assessed against the cytosolic human isoforms hCA I and hCA II, the transmembrane hCA IX as well as β- and γ-CAs from different bacterial and fungal strains, was evaluated by a stopped-flow CO₂ hydrase assay. Several of the investigated derivatives showed interesting inhibition activity towards the cytosolic associate isoforms hCA I and hCA II, as well as the three γ-CAs and Malassezia globosa (MgCA) enzyme. Six compounds (1b-1d, 1h, 1i and 1j) were more potent than AAZ against hCA I while five (1d, 1h, 1i, 1j and 4a) showed better activity than AAZ against the hCA II isoform. Moreover, all compounds appeared to be very potent against MgCA with a Ki lower than that of the reference drug. Furthermore, computational procedures were used to investigate the binding mode of this class of compounds within the active site of human CAs.

Deciphering the competitive inhibition of dihydropteroate synthase by 8 marcaptoguanine analogs: enhanced potency in phenylsulfonyl fragments

The emergence of sulfa-drug resistance and reduced efficacy of pterin-based analogs towards Dihydropteroate synthase (DHPS) inhibition dictate a pressing need of developing novel antimicrobial agents for immune-compromised patients. Recently, a series of 8-Marcaptoguanin (8-MG) derivatives synthesized for 6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (experimental K_D ∼ 100-.0.36) showed remarkable homology with the pteroic-acid and serve as a template for product antagonism in DHPS. The present work integrates ligand-based drug discovery techniques with structure-based docking, enhanced MD simulation, and MM/PBSA techniques to demonstrate the essential features of 8-MG analogs which make it a potent inhibitor for DHPS. The delicate balance in hydrophilic, hydrophobic substitutions on the 8-MG core is the crucial signature for DHPS inhibition. It is found that the dynamic interactions of active compounds are mainly dominated by consistent hydrogen bonding network with Asp 96, Asn 115, Asp 185, Ser 222, Arg 255 and π-π stacking, π-cation interactions with Phe 190, Lys 221. Further, two new 8-MG compounds containing N-phenylacetamide (compound S1, ΔG_bind-eff = -62.03 kJ/mol) and phenylsulfonyl (compound S3, ΔG_bind-eff = -71.29 kJ/mol) fragments were found to be the most potent inhibitor of DHPS, which stabilize the flexible pABA binding loop, thereby increasing their binding affinity. MM/PBSA calculation shows electrostatic energy contribution to be the principal component in stabilizing the inhibitors in the binding pocket. This fact is further confirmed by the higher energy barrier obtained in umbrella sampling for this class of inhibitors.

Synthesis, Physicochemical Properties and Molecular Docking of New Benzothiazole Derivatives as Antimicrobial Agents Targeting DHPS Enzyme

The drug-resistance problem is widely spread and becoming more common in community-acquired and nosocomial strains of bacteria. Therefore, finding new antimicrobial agents remains an important drug target. From this perspective, new derivatives of benzothiazole were synthesized and evaluated for their antimicrobial activity and ability to inhibit the DHPS enzyme. The synthesis was carried out by the reaction of benzothiazole N-arylsulphonylhydrazone with N-aryl-2-cyano-3-(dimethylamino)acrylamide, N-aryl-3-(dimethylamino)prop-2-en-1-one, arylaldehydes or diazonium salt of arylamine derivatives, which led to the formation of N-arylsulfonylpyridones 6a-d (yield 60-70%) and 12a-c (yield 50-60%),N-(2-(benzo[d]thiazole-2-yl)-3-arylacryloyl-4-methylsulfonohydrazide 14a-c (yield 60-65%), 4-(benzo[d]thiazole-2-yl)-5-aryl-1H-pyrazol-3(2H)-one 16a-c (yield 65-75%), and N'-(2-(benzo[d]thiazol-2-yl)-2-(2-arylhydrazono)acetyl)-4-arylsulfonohydrazide 19a-e (yield 85-70%). The antimicrobial evaluations resulted into a variety of microbial activities against the tested strains. Most compounds showed antimicrobial activity against S. aureus with an MIC range of 0.025 to 2.609 mM. The most active compound, 16c, exhibited superior activity against the S. aureus strain with an of MIC 0.025 mM among all tested compounds, outperforming both standard drugs ampicillin and sulfadiazine. The physicochemical-pharmacokinetic properties of the synthesized compounds were studied, and it was discovered that some compounds do not violate rule of five and have good bioavailability and drug-likeness scores. The five antimicrobial potent compounds with good physicochemical-pharmacokinetic properties were then examined for their inhibition of DHPS enzyme. According to the finding, three compounds, 16a-c, had IC₅₀ values comparable to the standard drug and revealed that compound 16b was the most active compound with an IC₅₀ value of 7.85 μg/mL, which is comparable to that of sulfadiazine (standard drug) with an IC₅₀ value of 7.13 μg/mL. A docking study was performed to better understand the interaction of potent compounds with the binding sites of the DHPS enzyme, which revealed that compounds 16a-c are linked by two arene-H interactions with Lys220 within the PABA pocket.

New thiazole-based derivatives as EGFR/HER2 and DHFR inhibitors: Synthesis, molecular modeling simulations and anticancer activity

New series of thiazole and imidazo[2,1-b]thiazole derivatives were synthesized and tested for their in vitro anticancer activity. Compounds 27, 34, 39 and 42-44 showed the best anticancer activity against the tested cancer cell lines with high safety profile and selectivity indices, especially MCF-7 breast cancer, compared to sorafenib. As an attempt to reveal their mode of cytotoxicity, EGFR, HER2 kinase and DHFR inhibition assays were performed. Compounds 39 and 43 were the most potent dual EGFR/HER2 kinase inhibitors, with IC₅₀ values of 0.153 (EGFR), 0.108 (HER2) and 0.122 (EGFR), 0.078 (HER2) μM, respectively. 39 and 42 were the best DHFR inhibitors showing IC₅₀ 0.291 and 0.123 μM, respectively. 39 and 43 induced their cytotoxicity via cell cycle arrest at G1/S and G1 phases, respectively, and apoptosis rather than necrosis in the MCF-7 breast cancer cell line. In vivo anti-breast cancer assay of 39 and 43 showed significant tumor volume reduction with recovered caspase-3 immunoexpression. Modeling study results proved the importance of the 5-(4-substituted phenyl)-imidazo[2,1-b]thiazole moiety and the hydrazide side chain for the anticancer activity. The most potent compounds showed good drug-likeness features and could be used as prototypes for further optimization. 39 could be an example of a multi-targeting anticancer agent that acts by inhibiting EGFR/HER2 kinase, DHFR enzymes and cellular apoptosis.

Novel Thiophene Thioglycosides Substituted with the Benzothiazole Moiety: Synthesis, Characterization, Antiviral and Anticancer Evaluations, and NS3/4A and USP7 Enzyme Inhibitions

Novel derivatives of benzothiazole-2-thiophene S-glycoside were synthesized and tested for their antiviral and anticancer potency and NS3/4A and USP7 enzyme inhibitions. The ring system was formed by first synthesizing new derivatives of 5-mercaptothiophene substituted with the benzothiazole moiety, followed by coupling with various halo sugar derivatives. New compounds were tested in vitro for the cytotoxic effect on five types of normal cell lines and for antiviral activity using a plaque reduction assay against CBV4, HSV-1, HCVcc genotype 4 viruses, HAV HM 175, and HAdV7. Notably, three compounds demonstrated substantial IC50, CC50, and SI values against HSV-1 with a viral reduction of 80% or more. Two substances have demonstrated a reduction of more than 50% in CBV4 and HCVcc viruses. The effectiveness of the compounds against HSV-1 and HCVcc was tested for their capability to inhibit NS3/4A protease and USP7 enzyme. Additionally, a panel of 60 human cancer cells was used to investigate the ability of the newly synthesized compounds to inhibit the in vitro tumor growth. The results revealed that two compounds, 6a and 6c, have an inhibitory effect on most cancer types, whereas 6d and 6f inhibited only three and two cell lines, respectively.

Synthesis of novel pyridine and pyrimidine thioglycoside phosphoramidates for the treatment of COVID-19 and influenza A viruses

A novel series of pyridine, cytosine, and uracil thioglycoside analogs (4a-i, 9a,b, and 13a,b, respectively) and their corresponding phosphoramidates (6a-I, 10a,b, and 14a,b, respectively) were synthesized and assessed for their antiviral inhibitory activities in a dual-pathogen screening protocol against SARS-CoV-2 and influenza A virus (IAV). MTT cytotoxicity (TC50) and plaque reduction assays were used to explore inhibition and cytotoxicity percentage values for H5N1 influenza virus strain and the half-maximal cytotoxic concentration (CC₅₀) and inhibitory concentration (IC₅₀) for SARS-CoV-2 virus. Most of the tested compounds demonstrated dose-dependent inhibition behavior. Both cytosine thioglycoside phosphoramidates 10a and 10b exhibited the most potent profiles with 83% and 86% inhibition at 0.25 µM concentration against H5N1 and IC₅₀ values of 12.16 µM, 14.9 µM against SARS-CoV-2, respectively. Moreover, compounds 10a and 10b have been shown to have the highest selectivity index (SI) among all the tested compounds against SARS-CoV-2 with 28.2 and 26.9 values, respectively.

Intracellular Bacterial Targeting by a Thiazolyl Benzenesulfonamide and Octaarginine Peptide Complex

A brominated thiazolyl benzenesulfonamide (BTB) derivative is conjugated with the cell-penetrating peptide octaarginine (R8) in an effort to construct innovative antibacterial products. The noncovalent complex of BTB and R8 is characterized by Fourier transform infrared (FTIR) spectroscopy, which indicates hydrogen bonding between the two constituents. Attachment of the peptide moiety renders aqueous solubility to the hydrophobic benzenesulfonamide drug and bestows bactericidal activity. Confocal imaging in conjunction with dye probes shows successful clearance of intracellular Staphylococcus aureus bacteria by the BTB-R8 complex. Scanning electron micrographs and studies with a set of fluorescent dyes suggest active disruption of the bacterial cell membrane by the BTB-R8 complex. In contrast, the complex of BTB with octalysine (K8) fails to cause membrane damage and displays a modest antibacterial effect. A complex of BTB with the water-soluble hydrophilic polymer poly(vinylpyrrolidone) (PVP) does not display any antibacterial effect, indicating the distinctive role of the cell-penetrating peptide (CPP) R8 in the cognate complex. The leakage of the encapsulated dye from giant unilamellar vesicles upon interaction with the BTB-R8 complex further highlights the membrane activity of the complex, which cannot be accomplished by bare sulfonamide alone. This work broadens the scope of use of CPPs with respect to eliciting antibacterial activity and potentially expands the limited arsenal of membrane-targeting antibiotics.

Pyrazolo[4,3-c]pyridine Sulfonamides as Carbonic Anhydrase Inhibitors: Synthesis, Biological and In Silico Studies

Carbonic anhydrases (CAs, EC 4.2.1.1) catalyze the essential reaction of CO2 hydration in all living organisms, being actively involved in the regulation of a plethora of patho-/physiological conditions. A series of chromene-based sulfonamides were synthesized and tested as possible CA inhibitors. On the other hand, in microorganisms, the β- and γ- classes are expressed in addition to the α- class, showing substantial structural differences to the human isoforms. In this scenario, not only human but also bacterial CAs are of particular interest as new antibacterial agents with an alternative mechanism of action for fighting the emerging problem of extensive drug resistance afflicting most countries worldwide. Pyrazolo[4,3-c]pyridine sulfonamides were synthesized using methods of organic chemistry. Their inhibitory activity, assessed against the cytosolic human isoforms hCA I and hCA II, the transmembrane hCA IX and XII, and β- and γ-CAs from three different bacterial strains, was evaluated by a stopped-flow CO2 hydrase assay. Several of the investigated derivatives showed interesting inhibition activity towards the cytosolic associate isoforms hCA I and hCA II, as well as the 3β- and 3γ-CAs. Furthermore, computational procedures were used to investigate the binding mode of this class of compounds within the active site of hCA IX. Four compounds (1f, 1g, 1h and 1k) were more potent than AAZ against hCA I. Furthermore, compound 1f also showed better activity than AAZ against the hCA II isoform. Moreover, ten compounds out of eleven appeared to be very potent against the γ-CA from E.coli, with a Ki much lower than that of the reference drug. Most of the compounds showed better activity than AAZ against hCA I as well as the γ-CA from E.coli and the β-CA from Burkholderia pseudomallei (BpsCAβ). Compounds 1f and 1k showed a good selectivity index against hCA I and hCA XII, while 1b was selective against all 3β-CA isoforms from E.coli, BpsCA, and VhCA and all 3γ-CA isoforms from E.coli, BpsCA and PgiCA.

Heme Protein Binding of Sulfonamide Compounds: A Correlation Study by Spectroscopic, Calorimetric, and Computational Methods

Protein-ligand interaction studies are useful to determine the molecular mechanism of the binding phenomenon, leading to the establishment of the structure-function relationship. Here, we report the binding of well-known antibiotic sulfonamide drugs (sulfamethazine, SMZ; and sulfadiazine, SDZ) with heme protein myoglobin (Mb) using spectroscopic, calorimetric, ζ potential, and computational methods. Formation of a 1:1 complex between the ligand and Mb through well-defined equilibrium was observed. The binding constants obtained between Mb and SMZ/SDZ drugs were on the order of 104 M-1. SMZ with two additional methyl (-CH3) substitutions has higher affinity than SDZ. Upon drug binding, a notable loss in the helicity (via circular dichroism) and perturbation of the three-dimensional (3D) protein structure (via infrared and synchronous fluorescence experiments) were observed. The binding also indicated the dominance of non-polyelectrolytic forces between the amino acid residues of the protein and the drugs. The ligand-protein binding distance signified high probability of energy transfer between them. Destabilization of the protein structure upon binding was evident from differential scanning calorimetry results and ζ potential analyses. Molecular docking presented the best probable binding sites of the drugs inside protein pockets. Thus, the present study explores the potential binding characteristics of two sulfonamide drugs (with different substitutions) with myoglobin, correlating the structural and energetic aspects.

Synthesis of some novel coumarin isoxazol sulfonamide hybrid compounds, 3D-QSAR studies, and antibacterial evaluation

With the progressive and ever-increasing antibacterial resistance pathway, the need for novel antibiotic design becomes critical. Sulfonamides are one of the more effective antibiotics against bacteria. In this work, several novel sulfonamide hybrids including coumarin and isoxazole group were synthesized in five steps starting from coumarin-3-carboxylic acid and 3-amino-5-methyl isoxazole and assayed for antibacterial activity. The samples were obtained in good to high yield and characterized by FT-IR, ¹³C-NMR, ¹H-NMR, CHN and melting point techniques. 3D-QSAR is a fast, easy, cost-effective, and high throughput screening method to predict the effect of the compound's efficacy, which notably decreases the needed price for experimental drug assay. The 3D-QSAR model displayed acceptable predictive and descriptive capability to find r2 and q2 the pMIC of the designed compound. Key descriptors, which robustly depend on antibacterial activity, perhaps were explained by this method. According to this model, among the synthesized sulfonamide hybrids, 9b and 9f had the highest effect on the gram-negative and gram-positive bacteria based on the pMIC. The 3D-QSAR results were confirmed in the experimental assays, demonstrating that our model is useful for developing new antibacterial agents. The work proposes a computationally-driven strategy for designing and discovering new sulfonamide scaffold for bacterial inhibition.

New Sulfanilamide Derivatives Incorporating Heterocyclic Carboxamide Moieties as Carbonic Anhydrase Inhibitors

Carbonic Anhydrases (CAs) are ubiquitous metalloenzymes involved in several disease conditions. There are 15 human CA (hCA) isoforms and their high homology represents a challenge for the discovery of potential drugs devoid of off-target side effects. For this reason, many synthetic and pharmacologic research efforts are underway to achieve the full pharmacological potential of CA modulators of activity. We report here a novel series of sulfanilamide derivatives containing heterocyclic carboxamide moieties which were evaluated as CA inhibitors against the physiological relevant isoforms hCA I, II, IX, and XII. Some of them showed selectivity toward isoform hCA II and hCA XII. Molecular docking was performed for some of these compounds on isoforms hCA II and XII to understand the possible interaction with the active site amino acid residues, which rationalized the reported inhibitory activity.

Antibacterial Activities and Molecular Docking of Novel Sulfone Biscompound Containing Bioactive 1,2,3-Triazole Moiety

In this study, a new synthetic 1,2,3-triazole-containing disulfone compound was derived from dapsone. Its chemical structure was confirmed using microchemical and analytical data, and it was tested for its in vitro antibacterial potential. Six different pathogenic bacteria were selected. MICs values and ATP levels were determined. Further, toxicity performance was measured using MicroTox Analyzer. In addition, a molecular docking study was performed against two vital enzymes: DNA gyrase and Dihydropteroate synthase. The results of antibacterial abilities showed that the studied synthetic compound had a strong bactericidal effect against all tested bacterial strains, as Gram-negative species were more susceptible to the compound than Gram-positive species. Toxicity results showed that the compound is biocompatible and safe without toxic impact. The molecular docking of the compound showed interactions within the pocket of two enzymes, which are able to stabilize the compound and reveal its antimicrobial activity. Hence, from these results, this study recommends that the established compound could be an outstanding candidate for fighting a broad spectrum of pathogenic bacterial strains, and it might therefore be used for biomedical and pharmaceutical applications.

Fragmentation of Polyfunctional Compounds Recorded Using Automated High-Throughput Desorption Electrospray Ionization

Using desorption electrospray ionization (DESI) as part of an automated high-throughput system, tandem mass spectra of the compounds in a pharmaceutical library were recorded in the positive mode under standardized conditions. Quality control filtering yielded an MS/MS library of 16 662 spectra. Fragmentation of subsets of the compounds in the library chosen to contain a single instance of a particular functional group (amide, piperazine, sulfonamide) was predicted by experts, and the results were compared with the experimental data. Expert performance was good to excellent for all the cases evaluated. Substituents on the functional groups were found to exert important secondary control over the fragmentation, with the main effect observed being product ion stabilization by aromatic substitution, which was consistent across the different groups evaluated. These substituent effects are generally explicable in terms of standard physical organic chemistry considerations of product ion stability as controlling fragmentation. A somewhat unexpected feature was the incidence of homolytic cleavages, driven by the stability of substituted amine radical cations. The findings of this study are intended to lay the groundwork for machine learning approaches to performing MS/MS spectrum → structure and structure → MS/MS spectrum operations on the same experimental data set. The effort involved and the success achieved in computer-aided interpretation, now underway, will be compared with the expert performance as described here.

Chromene-Containing Aromatic Sulfonamides with Carbonic Anhydrase Inhibitory Properties

Carbonic anhydrases (CAs, EC 4.2.1.1) catalyze the essential reaction of CO₂ hydration in all living organisms, being actively involved in the regulation of a plethora of patho/physiological conditions. A series of chromene-based sulfonamides were synthesized and tested as possible CA inhibitors. Their inhibitory activity was assessed against the cytosolic human isoforms hCA I, hCA II and the transmembrane hCA IX and XII. Several of the investigated derivatives showed interesting inhibition activity towards the tumor associate isoforms hCA IX and hCA XII. Furthermore, computational procedures were used to investigate the binding mode of this class of compounds, within the active site of hCA IX.

Structure based design, synthesis, and biological evaluation of imidazole derivatives targeting dihydropteroate synthase enzyme

In this study, we have designed and synthesized 2-((5-acetyl-1-(phenyl)-4-methyl-1H-imidazol-2-yl)thio)-N-(4-((benzyl)oxy)phenyl) acetamide derivatives. Antimicrobial activities of all the imidazole derivatives have been examined against Gram-positive and Gram-negative bacteria and results showed that the conjugates have appreciable antibacterial activity. Besides, several analogous were evaluated for their in vitro antiresistant bacterial strains such as Extended-spectrum beta-lactamases (ESBL), Vancomycin-resistant Enterococcus (VRE), and Methicillin-resistant Staphylococcus aureus (MRSA). The SAR revealed that the 12l compound resulted in potency against all bacterial strains as well as ESBL, VRE, and MRSA strains. Lipinski's rule of five, and ADME studies were preformed for all the synthesized compounds with Staphylococcus aureus dihydropteroate synthase (saDHPS) protein (PDB ID: 6CLV) and were found standard drug-likeness properties of conjugates. Moreover, the binding mode of the ligands with the protein study has been examined by molecular docking and results are quite promising. Besides, all the analogous were tested for their in vitro antituberculosis, antimalarial, and antioxidant activity.

Synthesis of new pyridines with sulfonamide moiety via a cooperative vinylogous anomeric-based oxidation mechanism in the presence of a novel quinoline-based dendrimer-like ionic liquid

In the present study, we reported the synthesis of a novel quinoline-based dendrimer-like ionic liquid. After characterization of the mentioned ionic liquid with suitable techniques such as Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDX), elemental mapping, thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG), its catalytic performance was investigated in the synthesis of new pyridines with sulfonamide moiety via a cooperative vinylogous anomeric-based oxidation mechanism under mild reaction conditions. All target molecules were achieved in short reaction times and high yields.

Novel Synthesis and Antiviral Evaluation of New Benzothiazole-Bearing N-Sulfonamide 2-Pyridone Derivatives as USP7 Enzyme Inhibitors

In this article, a series of benzothiazole-bearing N-sulfonamide 2-pyridone derivatives were synthesized via the reaction of benzothiazole sulfonylhydrazide with sodium salts of both (hydroxymethylene) cycloalkanones and unsaturated ketones, as well as ethoxymethylene derivatives. The structures of the resultant compounds were confirmed using IR, ¹H NMR, ¹³C NMR, ¹H-¹H correlation spectroscopy (COSY), ¹H-¹³C heteronuclear multiple bond coherence (HMBC), and ¹H-¹³C heteronuclear multiple quantum coherence (HSQC) spectral analysis and elemental analysis. The newly synthesized compounds were evaluated in vitro for their antiviral activities against the HSV-1, HAV HM175, HCVcc genotype 4, CBV4, and HAdV7 viruses. Additionally, the compounds were examined for their cytotoxic effect on five normal cell lines. It was observed that five compounds were found to possess viral reduction of 50% or more against CBV4 with significant IC₅₀, CC₅₀, and SI values. In the case of HSV-1 and HAV HM175 viruses, three compounds have shown more than 50% reduction, while in the case of HCVcc genotype 4 and HAdV7 viruses, only two compounds demonstrated more than 50% reduction. Furthermore, the physicochemical properties of the most active compounds were evaluated. The two most potent compounds against HSV-1 virus, 7e and 13a, were evaluated for their inhibitory activity against USP7. Docking studies using Molecular Operating Environment (MOE) were used to identify the interactions between 7e and 13a compounds and the active site of the USP7 enzyme.

Folic acid-sulfonamide conjugates as antibacterial agents: design, synthesis and molecular docking studies

Dihydrofolate reductase (DHFR) inhibitors, as antibacterial agents, contain pyrimidine, pteridine, and azine moieties among many other scaffolds. Folic acid (FA), with a pteridine ring and amine group, was used as our focus scaffold, which was then conjugated with sulfonamides to develop new conjugates. The novel synthesized conjugates were characterized using infrared spectroscopy, and ¹H and ¹³C nuclear magnetic resonance (NMR) spectral studies and consequently screened for antimicrobial activities against bacterial strains with ampicillin as a positive control. Compound DS2 has the highest zone of inhibition (36.6 mm) with a percentage activity index (%AI) value of 122.8% against S. aureus and a minimum inhibitory concentration (MIC) of 15.63 μg mL^-1. DHFR enzyme inhibition was also evaluated using the synthesized conjugates through in vitro studies, and inhibition assays revealed that compound DS2 exhibited a 75.4 ± 0.12% (mean ± standard error of the mean (SEM)) inhibition, which is comparable with the standard DHFR inhibitor trimethoprim (74.6 ± 0.09%). The compounds attached to the unsubstituted aryl moiety of the sulfonamides revealed better inhibition against the bacterial strains as compared to the methyl substituted aryl sulfonamides. Molecular docking studies of the novel synthesized conjugates were also performed on the DHFR enzyme to identify the plausible binding modes to explore the binding mechanisms of these conjugates.

Dual-Target Inhibitors of the Folate Pathway Inhibit Intrinsically Trimethoprim-Resistant DfrB Dihydrofolate Reductases

Trimethoprim (TMP) is widely used to treat infections in humans and in livestock, accelerating the incidence of TMP resistance. The emergent and largely untracked type II dihydrofolate reductases (DfrBs) are intrinsically TMP-resistant plasmid-borne Dfrs that are structurally and evolutionarily unrelated to chromosomal Dfrs. We report kinetic characterization of the known DfrB family members. Their kinetic constants are conserved and all are poorly inhibited by TMP, consistent with TMP resistance. We investigate their inhibition with known and novel bisubstrate inhibitors of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK). Importantly, all are inhibited by the HPPK inhibitors, making these molecules dual-target inhibitors of two folate pathway enzymes that are strictly microbial.

Design and Synthesis of a New Class of Pyridine-Based N-Sulfonamides Exhibiting Antiviral, Antimicrobial, and Enzyme Inhibition Characteristics

A new strategy for designing and assembling a novel class of functionalized pyridine-based benzothiazole and benzimidazole incorporating sulfonamide moieties was developed. The synthesis was carried out by reacting N-cyanoacetoarylsulfonylhydrazide with various electrophiles such as 2-(benzo[d]thiazol-2-yl)-3,3-bis(alkylthio)acrylonitriles and 2-(benzo[d]imidazol-2-yl)-3,3-bis(methylthio)-acrylonitriles, as well as 2-ethoxyl acrylonitrile derivatives. The synthesized compounds were tested for their antiviral and antimicrobial potency. Two of the synthesized compounds, 15c and 15d, showed more than 50% viral reduction against HSV-1 and CBV4, with significant IC₅₀ and CC₅₀ values. The two potent compounds 15c and 15d have also shown inhibitory activity against Hsp90α protein with IC₅₀ values of 10.24 and 4.48 μg/mL, respectively. A combination of 15c and 15d with acyclovir has led to IC₅₀ values that are lower than that of acyclovir alone. Molecular modeling studies were used to identify the interactions between the 15c and 15d compounds and the active site of Hsp90α enzyme. The antimicrobial investigation of the new compounds has also shown that 8b and 15d exhibited a higher inhibition zone (IZ) than sulfadiazine and gentamicin against Klebsiella pneumonia, whereas 9a showed higher IZ than ampicillin against Staphylococcus aureus. According to the enzyme assay study on dihydrofolate reductase, 9a was shown to be the most potent compound among all examined compounds.

Tailored-design of electrospun nanofiber cellulose acetate/poly(lactic acid) dressing mats loaded with a newly synthesized sulfonamide analog exhibiting superior wound healing

To effectively allow for controlled release of a newly synthesized sulfonamide analog, biodegradable poly(lactic acid) nanofibrous dressing mats tailored-designed for maximum wound healing efficacy were developed. The heterocyclic analog, N-(3,4-diamino-7-(benzo [d]thiazol-2-yl)-6-oxo-1H-pyrazolo[4,3-c]pyridin-5(6H)-yl)benzenesulfonamide, has been specifically synthesized to possess superior antibacterial and anti-inflammatory characteristics. Hydrophilic cellulose acetate and/or poly(ethylene oxide) were blended with the hydrophobic PLA to control the hydrophilicity/hydrophobicity ratio for the sustained release of the drug. SEM detected no drug crystals on the surface of the nanofibers confirming the homogeneous dispersion and compatibility of the drug with the nanofibers. BET indicated almost-reversible Type II sorption isotherms. The swelling studies revealed that the presence of hydrogen bonds between the hydroxyl groups of CA with the carbonyl ester groups of PLA limited the ability of CA molecules to leach from the polymer matrix. Water vapor permeability were all determined to be within the range of 15-19 g/m²/h. In-vitro cell viability and cell proliferation studies revealed the superiority of the fabricated dressing mats in terms of its bioactivity and cellular interaction. In-vivo studies confirmed the major improvement in its wound healing capabilities attributed to an enhanced epithelization, anti-inflammation, neo-angiogenesis, fibroplasias and collagen deposition that surpassed that of commercially available ones.