Synthesis and structure-activity relationship studies of 4-arylthiosemicarbazides as topoisomerase IV inhibitors with Gram-positive antibacterial activity. Search for molecular basis of antibacterial activity of thiosemicarbazides

Thiosemicarbazone-Based Compounds: A Promising Scaffold for Developing Antibacterial, Antioxidant, and Anticancer Therapeutics

This paper presents the synthesis and characterization of new thiosemicarbazone derivatives with potential applications as antibacterial, antioxidant and anticancer agents. Six thiosemicarbazone derivatives (L-L5) were synthesized by reacting an appropriate thiosemicarbazide derivative with 2-pyridinecarboxaldehyde. The structures of the obtained compounds were confirmed using mass spectrometry, infrared spectroscopy, and NMR spectroscopy. Antibacterial activity was evaluated by using the microdilution method, determining the minimum inhibitory concentration (MIC) against a panel of Gram-positive and Gram-negative bacteria. Compound L1 showed the most potent antibacterial activity, especially against Bacillus cereus (MIC 10 mg/L). Molecular docking to topoisomerase II and transcriptional regulator PrfA suggests that the studied compounds can effectively bind to molecular targets recognized in anticancer and antibacterial therapies. An assessment of physicochemical properties (ADME) indicates favorable parameters of the compounds as potential drugs. Compounds L and L2 showed the highest antioxidant activity, surpassing the activity of the Trolox standard. Cytotoxicity against A549 lung cancer cells was evaluated by the MTT assay. Compound L4 exhibited the strongest inhibitory effect on cancer cell survival. The obtained results indicate that the synthesized thiosemicarbazide derivatives, especially L1, L2, and L4, are promising compounds with potential applications as antibacterial and anticancer drugs.

Synthesis, molecular modelling and antibacterial activity of 4-aryl-thiosemicarbazides

N-Substituted phenyl/cyclohexyl-2-(pyridine-4-carbonyl) hydrazine-1-carbothioamides (2a–r) were synthesized, characterized by spectral and analytical data. The compounds were evaluated for antibacterial activity by the disc diffusion method. Most of the compounds showed activity against Gram-positive bacteria. Compound 2h with 4-Sulfapyrimidine phenyl substitution was found to be the most promising candidate, active against Gram-positive and methicillin-resistant Staphylococcus aureus (MRSA) strains with minimum inhibitory concentration (MIC) of (2–7 μg/mL). From the docking study, we predicted that compounds (2r, 2g, 2h, 2o, 2p and 2e) possess better antibacterial activity by having a good binding affinity with target protein and they could be used as potential drugs as antimicrobials. Amongst all the docked compounds, the compound 2h presented near binding affinity & interaction docking score with DNA gyrase enzymes with reference to ciprofloxacin.

Thiosemicarbazide Derivatives Decrease the ATPase Activity of Staphylococcus aureus Topoisomerase IV, Inhibit Mycobacterial Growth, and Affect Replication in Mycobacterium smegmatis

Compounds targeting bacterial topoisomerases are of interest for the development of antibacterial agents. Our previous studies culminated in the synthesis and characterization of small-molecular weight thiosemicarbazides as the initial prototypes of a novel class of gyrase and topoisomerase IV inhibitors. To expand these findings with further details on the mode of action of the most potent compounds, enzymatic studies combined with a molecular docking approach were carried out, the results of which are presented herein. The biochemical assay for 1-(indol-2-oyl)-4-(4-nitrophenyl) thiosemicarbazide (4) and 4-benzoyl-1-(indol-2-oyl) thiosemicarbazide (7), showing strong inhibitory activity against Staphylococcus aureus topoisomerase IV, confirmed that these compounds reduce the ability of the ParE subunit to hydrolyze ATP rather than act by stabilizing the cleavage complex. Compound 7 showed better antibacterial activity than compound 4 against clinical strains of S. aureus and representatives of the Mycobacterium genus. In vivo studies using time-lapse microfluidic microscopy, which allowed for the monitoring of fluorescently labelled replisomes, revealed that compound 7 caused an extension of the replication process duration in Mycobacterium smegmatis, as well as the growth arrest of bacterial cells. Despite some similarities to the mechanism of action of novobiocin, these compounds show additional, unique properties, and can thus be considered a novel group of inhibitors of the ATPase activity of bacterial type IIA topoisomerases.

Antibacterial Activity of Fluorobenzoylthiosemicarbazides and Their Cyclic Analogues with 1,2,4-Triazole Scaffold

The development of drug-resistant bacteria is currently one of the major challenges in medicine. Therefore, the discovery of novel lead structures for the design of antibacterial drugs is urgently needed. In this structure-activity relationship study, a library of ortho-, meta-, and para-fluorobenzoylthiosemicarbazides, and their cyclic analogues with 1,2,4-triazole scaffold, was created and tested for antibacterial activity against Gram-positive bacteria strains. While all tested 1,2,4-triazoles were devoid of potent activity, the antibacterial response of the thiosemicarbazides was highly dependent on substitution pattern at the N4 aryl position. The optimum activity for these compounds was found for trifluoromethyl derivatives such as 15a, 15b, and 16b, which were active against both the reference strains panel, and pathogenic methicillin-sensitive and methicillin-resistant Staphylococcus aureus clinical isolates at minimal inhibitory concentrations (MICs) ranging from 7.82 to 31.25 μg/mL. Based on the binding affinities obtained from docking, the conclusion can be reached that fluorobenzoylthiosemicarbazides can be considered as potential allosteric d-alanyl-d-alanine ligase inhibitors.

Recent advancements in the medicinal chemistry of bacterial type II topoisomerase inhibitors

Replication proteins are sought as a potential targets for antimicrobial agents. Despite their promising target characteristics, only topoisomerase II inhibitors targeting DNA gyrase and/or topoisomerase IV have reached clinical use. Topoisomerases are the enzymes that are essential for cellular functions and various biological activities. A wide range of natural and synthetic compounds have been identified as potential topoisomerase inhibitors but the resistance is most commonly found in these drugs. The emergence of FQ resistance has increased the need for the development of novel topoisomerase inhibitors with efficacy and high potency against FQ-resistant strains. Besides structural modifications of existing FQ scaffolds, novel non-quinolone topoisomerase II inhibitors, known as novel bacterial topoisomerase inhibitors, have been developed which showed remarkable inhibitory activity against DNA gyrase/topoisomerase IV or both with an improved spectrum of antibacterial potency including drug-resistant strains. This review aims to summarize various recent advancements in the medicinal chemistry of topoisomerase inhibitors with the following objectives: (1) To represent inclusive data on types of topoisomerases and various marketed topoisomerase inhibitors as drugs; (2) To discuss the recent advances in the medicinal chemistry of various topoisomerase inhibitors (DNA gyrase and topo IV) belonging to different structural classes as potential antibacterial agents; (3) To summarizes the structure activity relationship (SAR) including in silico and mechanistic studies to afford ideas and to provide focused direction for the development of new chemical entities which are effective against drug-resistant bacterial pathogens and biofilms.

Investigation of thiosemicarbazide free or within chitosan nanoparticles in a murine model of vulvovaginal candidiasis

Vulvovaginal candidiasis is a serious health problem affecting numerous women around the world. Its treatment is based on antifungals which may not provide an effective cure because of the resistance presented by its etiological pathogens Candida spp. Candida albicans is the most prevalent species related to vulvovaginal candidiasis. Here, we evaluated the in vivo antifungal potential of thiosemicarbazide and thiosemicarbazide encapsulated within chitosan nanoparticles in a murine model of vulvovaginal candidiasis. The results demonstrated the antifungal capacity of free or nanoencapsulated thiosemicarbazide within chitosan to reduce the fungal load in the vaginal tissue of infected mice. In addition, histological analyses indicated the absence or a mild to moderate infection in thiosemicarbazide-treated groups. Statistical tests confirmed the existence of significant differences between the treated and the control groups. Therefore, our results suggest a potential application of thiosemicarbazide and encapsulated thiosemicarbazide as an alternative vulvovaginal candidiasis therapy.

Systematic Identification of Thiosemicarbazides for Inhibition of Toxoplasma gondii Growth In Vitro

One of the key stages in the development of new therapies in the treatment of toxoplasmosis is the identification of new non-toxic small molecules with high specificity to Toxoplasma gondii. In the search for such structures, thiosemicarbazide-based compounds have emerged as a novel and promising leads. Here, a series of imidazole-thiosemicarbazides with suitable properties for CNS penetration was evaluated to determine the structural requirements needed for potent anti-Toxoplasma gondii activity. The best 4-arylthiosemicarbazides 3 and 4 showed much higher potency when compared to sulfadiazine at concentrations that are non-toxic to the host cells, indicating a high selectivity of their anti-toxoplasma activity.

Piperazine-azole-fluoroquinolone hybrids: Conventional and microwave irradiated synthesis, biological activity screening and molecular docking studies

A series of new 1,2,4-triazole and 1,3,4-oxadiazole derivatives was obtained via several steps sequential reactions of phenyl piperazine. Then, these compounds were converted to the corresponding fluoroquinolone hybrids via one pot three component Mannich reaction. All the reactions were examined under conventional and microwave mediated conditions, and optimum conditions were determined. The effect of different solvents and microwave power on microwave prompted reactions was investigated as well. All the newly synthesized compounds were characterized by FTIR, ¹H NMR, ¹³C NMR and EI MS spectral techniques. The antimicrobial activity, DNA gyrase and Topoisomerase IV inhibition potentials were performed. The results obtained showed that fluoroquinolone hybrids possess good antimicrobial activity. Moreover, Fluoroquinolone-azole-piperazine hybrids synthesized in the present study displayed excellent DNA gyrase inhibition. To unveil the interaction mode of compounds to receptor, a molecular docking study was performed. With an average least binding energy of -9.5 kcal/mol, all compounds were found to have remarkable inhibitory potentials against DNA gyrase (E. coli).

Synthesis and Antibacterial Activity of New Thiazolidine-2,4-dione-Based Chlorophenylthiosemicarbazone Hybrids

Series of new thiazolidine-2,4-dione-based chlorophenylthiosemicarbazone hybrids (17–40) were synthesized by the reaction of condensation chlorophenylthiosemicarbazides with formylphenyl 2-(2,4-dioxothiazolidin-5-yl/ylidene)acetates. New compounds were tested on reference strains of Gram-positive and Gram-negative bacteria. The antibacterial activity of target compounds was determined by broth dilution method. Most active compounds possess minimum inhibitory concentration (MIC) = 3.91 mg/L. These compounds were non-toxic at concentrations close to their antibacterial effect. The antibacterial activity of some compounds was similar to or higher than the activity of used reference drugs such as oxacillin and cefuroxime. The structure–activity relationships (SARs) analysis collectively suggests that at least two different molecular mechanisms of their antibacterial activity should be expected.

4-Cyclohexyl-1-(2-methoxybenzoyl)thiosemicarbazide with an unknown solvent

In the title compound, C15H21N3O2S, a short intramolecular N—H...O hydrogen bond generates anS(6) ring. The molecule is twisted with a dihedral angle between the benzene ring and the mean plane of the cyclohexyl ring being 58.90 (6)°. In the crystal, inversion dimers are formed with each molecule linked to the other by two N—H(H)...O hydrogen bonds to the same acceptor, generatingR21(6) loops. A region of disordered electron density was corrected for using the SQUEEZE routine inPLATON[Spek (2015).ActaCryst. C71, 9–18]. The given chemical formula and other crystal data do not take into account the unknown solvent molecule(s).

Lipophilicity Studies on Thiosemicarbazide Derivatives

The lipophilicity of two series of thiosemicarbazide derivatives was assessed by the RP-HPLC method with the RP-18 chromatographic column and the methanol–water mixture as the mobile phase. Distribution coefficients logP_HPLC were compared to calculated values generated by commonly used AClogP software and quantum chemical calculations. The reliability of the predictions was evaluated using the correlation matrix and PCA. For 4-benzoylthiosemicarbazides, a high correlation between theoretical and experimental logP parameters was obtained using the XlogP3 algorithm, while for 4-aryl/(cyclohexyl)thiosemicarbazides, the XlogP2 parameter was strongly correlated with the experimentally obtained logP.

Antistaphylococcal Activity of Selected Thiourea Derivatives

Five of thiourea derivatives were prepared using as a starting compound 3-(trifluoromethyl)aniline, 4-chloro-3-nitroaniline, 1,3-thiazol-2-amine, 2H-1,2,3-triazol-4-amine and commercial isothiocyanates. All compounds were evaluated in vitro for antimicrobial activity. Derivatives 2 and 3 showed the highest inhibition against Gram-positive cocci (standard and hospital strains). The observed MIC values were in the range of 0.5–8 μg/ml. The products effectively inhibited the formation of biofilms of methicillin-resistant and standard strains of Staphylococcus epidermidis. Inhibitory activity of thioureas 2 and 3 against Staphylococcus aureus topoisomerase IV was studied. The examined compounds were nongenotoxic.

Biological evaluation and molecular modelling study of thiosemicarbazide derivatives as bacterial type IIA topoisomerases inhibitors

In the present article, we describe the inhibitory potency of nine thiosemicarbazide derivatives against bacterial type IIA topoisomerases, their antibacterial profile and molecular modelling evaluation. We found that one of the tested compounds, compound 7, significantly inhibits activity of Staphylococcus aureus DNA gyrase with an IC(50) below 15 μM. Besides, this compound displays antibacterial activity on reference Staphylococuss spp. and Enterococcus faecalis strains as well as clinical S. aureus isolates at non-cytotoxic concentrations in mammalian cells with MIC values ranging from 16 to 32 μg/mL thereby indicating, in some cases, equipotent or even more effective action than standard drugs such as vancomycin, ampicillin and nitrofurantoin. The computational studies showed that both molecular geometry and the electron density distribution have a great impact on antibacterial activity of thiosemicarbazide derivatives.

Synthesis, cytotoxicity and antimicrobial activity of thiourea derivatives incorporating 3-(trifluoromethyl)phenyl moiety

A total of 31 of thiourea derivatives was prepared reacting 3-(trifluoromethyl)aniline and commercial aliphatic and aromatic isothiocyanates. The yields varied from 35% to 82%. All compounds were evaluated in vitro for antimicrobial activity. Derivatives 3, 5, 6, 9, 15, 24 and 27 showed the highest inhibition against Gram-positive cocci (standard and hospital strains). The observed MIC values were in the range of 0.25-16 μg/ml. Inhibitory activity of thioureas 5 and 15 against topoisomerase IV isolated from Staphylococcus aureus was studied. Products 5 and 15 effectively inhibited the formation of biofilms of methicillin-resistant and standard strains of Staphylococcus epidermidis. Moreover, all obtained thioureas were evaluated for cytotoxicity and antiviral activity against a large panel of DNA and RNA viruses. Compounds 5, 6, 8-12, 15 resulted cytotoxic against MT-4 cells (CC50 ≤ 10 μM).

Design, synthesis and biological evaluation of 4-benzoyl-1-dichlorobenzoylthiosemicarbazides as potent Gram-positive antibacterial agents

Twelve 4-benzoyl-1-dichlorobenzoylthiosemicarbazides have been tested as potential antibacterials. All the compounds had MICs between 0.49 and 15.63 µg/ml toward Micrococcus luteus, Bacillus cereus, Bacillus subtilis and Staphylococcus epidermidis indicating, in most cases, equipotent or even more effective action than cefuroxime. In order to clarify if the observed antibacterial effects are universal, further research were undertaken to test inhibitory potency of two most potent compounds 3 and 11 on clinical isolates of Staphylococcus aureus. Compound 11 inhibited the growth of methicillin-sensitive S. aureus (MSSA) at MICs of 1.95-7.81 µg/ml, methicillin-resistant S. aureus (MRSA) at MICs of 0.49-1.95 µg/ml and MDR-MRSA at MIC of 0.98 and 3.90 µg/ml, respectively. Finally, inhibitory efficacy of 3 and 11 on planktonic cells and biofilms formation in clinical isolates of S. aureus and Haemophilus parainfluenzae was tested. The majority of cells in biofilm populations of MSSA and MRSA were eradicated at low level of 3, with MBICs in the range of 7.82-15.63 µg/ml.

N-substituted indole carbohydrazide derivatives: synthesis and evaluation of their antiplatelet aggregation activity

Background

Platelet aggregation is one of the most important factors in the development of thrombotic disorders which plays a central role in thrombosis (clot formation). Prophylaxis and treatment of arterial thrombosis are achieved using anti-platelet drugs. In this study, a series of novel substituted indole carbohydrazide was synthesized and evaluated for anti-platelet aggregation activity induced by adenosine diphosphate (ADP), arachidonic acid (AA) and collagen.

Methods

Our synthetic route started from methyl 1H-indole-3-carboxylate (1) and ethyl 1H-indole-2-carboxylate (4) which were reacted with hydrazine monohydrate 99%. The aldol condensation of the later compound with aromatic aldehydes led to the formation of the title compounds. Sixteen indole acylhydrazone derivatives, 3d-m and 6d-i were tested for anti-platelet aggregation activity induced by adenosine diphosphate (ADP), arachidonic acid (AA) and collagen.

Results

Among the synthesized compounds, 6g and 6h with 100% inhibition, proved to be the most potent derivatives of the 2-substituted indole on platelet aggregation induced by AA and collagen, respectively. In 3-substituted indole 3m with 100% inhibition and 3f and 3i caused 97% inhibition on platelet aggregation induced by collagen and AA, respectively.

Conclusion

In this study, compounds 6g, 6h, 3m, 3f and 3i showed better inhibition on platelet aggregation induced by AA and collagen among the title compounds. Quantitative structure–activity relationship (QSAR) analysis between the structural parameters of the investigated derivatives and their antiplatelet aggregation activity was performed with various molecular descriptors but, analysis of the physicochemical parameters doesn’t show a significant correlation between the observed activities and general molecular parameters of the synthesized derivatives. Although, due to the existence of several receptors on the platelets surface which are responsible for controlling the platelet aggregation, the investigated compounds in the present study may exert their activities through binding to more than one of these receptors and therefore no straight forward SAR could be obtained for them.

Structure-activity relationship studies of microbiologically active thiosemicarbazides derived from hydroxybenzoic acid hydrazides

Forty-five derivatives of thiosemicarbazide were synthesized, and their antibacterial activity against Gram-positive and Gram-negative bacteria was evaluated. Some of the described compounds exhibited interesting activity against reference strains of Gram-positive bacteria, whereas only two derivatives had the ability to inhibit the growth of Gram-negative species (Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 13883, Proteus mirabilis ATCC 12453). The most potent antimicrobial activity was observed in the cases of salicylic acid hydrazide derivatives. The differences in activity inspired us to conduct conformational analysis using molecular mechanics level. The obtained results suggest that the molecule geometry, especially at the N4-terminus of thiosemicarbazide skeleton, determines the antibacterial activity. Unfortunately, in opposition to what we expected, only one of the tested compounds inhibited the activity of the topoIV enzyme, and none of them was active against DNA gyrase.

1,4-Disubstituted thiosemicarbazide derivatives are potent inhibitors of Toxoplasma gondii proliferation

A series of 4-arylthiosemicarbazides substituted at the N1 position with a 5-membered heteroaryl ring was synthesized and evaluated in vitro for T. gondii inhibition proliferation and host cell cytotoxicity. At non-toxic concentrations for the host cells all studied compounds displayed excellent anti-parasitic effects when compared to sulfadiazine, indicating a high selectivity of their anti-T. gondii activity. The differences in bioactivity investigated by DFT calculations suggest that the inhibitory activity of 4-aryl-thiosemicarbazides towards T. gondii proliferation is connected with the electronic structure of the molecule. Further, these compounds were tested as potential antibacterial agents. No growth-inhibiting effect on any of the test microorganisms was observed for all the compounds, even at high concentrations.

Synthesis of novel 4-nitropyrrole-based semicarbazide and thiosemicarbazide hybrids with antimicrobial and anti-tubercular activity

We report the synthesis and screening of forty novel 4-nitropyrrole-semicarbazide conjugates inspired from the reported bio-potential of bromopyrrole alkaloids and semicarbazide derivatives for antimicrobial activity. Herein, hybrids 5k-5o, 5r, 5s and 5t displayed four-fold increased activity (MIC=0.39 μg/mL) against Escherichia coli compared to standard ciprofloxacin. Eight hybrids, 5k-5o and 5r-5t displayed equal antibacterial activity (MIC=1.56 μg/mL) against Klebsiella pneumonia compared to standard ciprofloxacin. Hybrid, 5k-5o (MIC=0.195 μg/mL) displayed highly potent antibacterial activity against MSSA as compared to standard ciprofloxacin. Eight-fold superior activity was observed for four hybrids 5k-5m and 5o (MIC=0.39 μg/mL) against MRSA. Further, nine hybrids displayed four-fold superior antifungal activity (MIC=0.78 μg/mL) compared to standard Amphotericin B. Encouraging MICs of these hybrids recognize them as promising leads for development of potential antimicrobial drugs.

Pharmacological and structure-activity relationship evaluation of 4-aryl-1-diphenylacetyl(thio)semicarbazides

This article describes the synthesis of six 4-aryl-(thio)semicarbazides (series a and b) linked with diphenylacetyl moiety along with their pharmacological evaluation on the central nervous system in mice and computational studies, including conformational analysis and electrostatic properties. All thiosemicarbazides (series b) were found to exhibit strong antinociceptive activity in the behavioural model. Among them, compound 1-diphenylacetyl-4-(4-methylphenyl)thiosemicarbazide 1b was found to be the most potent analgesic agent, whose activity is connected with the opioid system. For compounds from series a significant anti-serotonergic effect, especially for compound 1-diphenylacetyl-4-(4-methoxyphenyl)semicarbazide 2b was observed. The computational studies strongly support the obtained results.

Synthesis and anti-Candidal activity of N-(4-aryl/cyclohexyl)-2-(pyridine-4-yl carbonyl) hydrazinecarbothioamide

Eighteen N-(4-aryl/cyclohexyl)-2-(pyridine-4-yl carbonyl) hydrazinecarbothioamide derivatives were synthesized, evaluated against ten clinical isolates of Candida spp. and compared with itraconazole. Introduction of p-chloro (2c), p-iodo (2q), m-chloro (2l) and o-nitro (2r) substitution at phenyl ring of thiosemicarbazide enhanced the anti-Candida activity. Compound (2c) bearing p-cholorophenyl ring was found to be the most effective against Candida albicans ATCC 66027, Candida spp. 12810 (blood) and Candida spp. 178 (HVS) with MIC value of 0.09-0.78 μg/mL, whereas itraconazole exhibits the inhibitory activity with MIC value of 0.04-1.56 μg/mL against all tested strains. There is a correlation between anti-Candidal activity and p-chloro substitution at phenyl ring of thiosemicarbazide. All synthesized compounds were investigated for their potential cytotoxicity against non cancer cell line MCF-10A. The active compounds 2c, 2r and 2a were further investigated for their cytotoxic effects on three cancer cell lines; HT1080 (skin), HepG2 (liver) and A549 (lung). The active compounds showed minimal cytotoxic activity against non cancer cell line and all three cancer cell lines. Moreover, compound 2c displaying better activity against C. albicans ATCC66027 and Candida spp. [blood] compared to reference drug (itraconazole), represents a good lead for the development of newer, potent and broad spectrum anti-Candidal agents.

Synthesis and evaluation of antimicrobial activity of hydrazones derived from 3-oxido-1H-imidazole-4-carbohydrazides

In this work we reported the synthesis and evaluation of in vitro antimicrobial activities of hydrazones 6 obtained from 3-oxido-1H-imidazole-4-carbohydrazides 4. All new compounds were characterized by spectroscopic methods. Hydrazones 6 were tested for their in vitro antimicrobial activity against four Gram-positive and four Gram-negative strains of bacteria as well as one fungal species. Three of the tested compounds appeared to be promising agents against reference strains of Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis. They were also tested against twelve clinical isolates of S. aureus and their cytotoxic effect on murine fibroblasts and HeLa human tumor cell line was determined.

Cytotoxic effect and molecular docking of 4-ethoxycarbonylmethyl-1-(piperidin-4-ylcarbonyl)-thiosemicarbazide--a novel topoisomerase II inhibitor

The preliminary cytotoxic effect of 4-ethoxycarbonylmethyl-1-(piperidin-4-ylcarbonyl)-thiosemicarbazide hydrochloride (1)-a potent topoisomerase II inhibitor-was measured using a MTT assay. It was found that the compound decreased the number of viable cells in both estrogen receptor-positive MCF-7 and estrogen receptor-negative MDA-MB-231breast cancer cells, with IC(50) values of 146 ± 2 and 132 ± 2 μM, respectively. To clarify the molecular basis of the inhibitory action of 1, molecular docking studies were carried out. The results suggest that 1 targets the ATP binding pocket.

Antifungal effect of 4-arylthiosemicarbazides against Candida species. Search for molecular basis of antifungal activity of thiosemicarbazide derivatives

The in vitro antifungal potency of six series of 4-arylthiosemicarbazides was evaluated. Two isoquinoline derivatives with an ortho-methoxy or ortho-methyl group at the phenyl ring were the most potent antifungal agents. Molecular modeling studies and docking of all 4-arylthiosemicarbazides into the active sites of sterol 14α-demethylase (CYP51), topoisomerase II (topo II), l-glutamine: d-fructose-6-phosphate amidotransferase (GlcN-6-P), secreted aspartic proteinase (SAP), N-myristoyltransferase (NMT), and UDP-N-acetylmuramoyl-l-alanine:d-glutamate ligase (MurD) indicated the importance of both structural and electronic factors in ligand recognition and thus for the antifungal effectiveness of 4-arylthiosemicarbazides. A possible antifungal target was identified (NMT) and isoquinoline-thiosemicarbazides showed more favorable affinity than the native ligand.

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