Structural analyses of Candida albicans sterol 14α-demethylase complexed with azole drugs address the molecular basis of azole-mediated inhibition of fungal sterol biosynthesis

Evaluation of the Antifungal Properties of Azomethine-Pyrazole Derivatives from a Structural Perspective

About 95 % of candidiasis infections worldwide are attributed to five Candida fungi species, with C. albicans being the most prevalent and severe. Due to resistance phenomena, the last decade has seen a significant challenge for candidiasis treatment with antifungal drugs, which has led to an urgent need for new antifungal agents. In this article, we report the synthesis of a series of azomethine-pyrazole derivatives bearing a para-substituted azo-phenyl ring. These compounds were evaluated as antifungal agents against Candida species and Cryptococcus neoformans strains. Compound ClAzoNH, substituted by chloride, displayed the highest toxicity on Candida albicans, with an MIC50 value of 2.08 μg/mL, while methoxy-substituted MeOAzoNH showed moderate inhibitory activity. The unsubstituted AzoNH compound exhibited the highest activity towards Candida tropicalis, Candida glabrata, Candida parapsilosis, and Candida krusei strains. In the case of C. albicans, the CaCYP51 protein appears to be the most probable biological target, while for C. neoformans, interactions with the CnFTase protein explained the in vitro results.

Azole resistance: patterns of amino acid substitutions in Candida sterol 14α-demethylase

The emergence of azole-resistant Candida infections is a major concern. A key mechanism is the gain of resistance through amino acid substitutions in the sterol 14α-demethylase, the main target of azole drugs. While numerous resistant substitutions are known, the pattern of such substitutions remains unclear. We hypothesized that resistant substitutions occur disproportionately at azole-binding sites. We compiled 2222 instances of azole-resistant substitutions from the literature and performed extensive computational sequence analyses. Altogether, there were 169 known substitutions at 133 sites in sterol 14α-demethylases of seven Candida species, whereas C. albicans alone had 120 substitutions at 97 sites. Just 10 sites and 18 substitutions (such as Y132F/H, K143R, D116E, and G464S) accounted for 75% of the total instances. Only about 48% of the sites were present within previously recognized hotspot regions, while just 33% of the azole-interacting residues had known resistant substitutions, most of them with only a few instances. The literature data on azole-resistant substitutions in Candida appear to be highly biased, as a few substitutions, such as Y132F/H and K143R, were preferentially sought and reported with over 1,000 instances. Additionally, there were numerous reports of "resistant" substitutions in azole-susceptible Candida isolates. Our study provides new perspectives into azole resistance.

New Methyl and Ethyl Gallate Esters Linked Chlorinated Benzoyl Derivatives as Anti-Candida albicans Agents: Isolation, Semi-Synthesis, In Vitro and In Silico Studies

Fungal infections caused by pathogenic fungi, particularly Candida albicans, range from oral thrush to severe systemic infections, especially in immunocompromised individuals. To address this, we employed a single-step reaction procedure to esterify methyl gallate (MG) and ethyl gallate (EG), isolated from the EtOAc-soluble fraction of the hydromethanolic leaf extract of Vachellia nilotica L. (Fabaceae), using substituted benzoyl chlorides. The structures of the synthesized ester analogs (MG1-MG4 and EG1-EG4) were characterized using UV, FT-IR, NMR, and mass spectrometry. Among them, MG1 showed the highest C. albicans inhibition (83.8%). Molecular docking analysis against C. albicans 14α-demethylase (CaCYP51) revealed a binding free energy (∆Gbind) of -33.08 kcal/mol for MG1, which is comparable to that of fluconazole (-36.91 kcal/mol) and consistent with the in vitro results. MD simulation demonstrated good stability of complex-MG1 throughout the simulation, with fluctuations remaining below 4.0 Å. In the active site, fluconazole formed a hydrogen bond with T267, while MG1 interacted with Y461 via hydrogen bonding. Given the close alignments between in vitro and in silico results, MG1 is identified as a potential C. albicans inhibitor, although alternative inhibition mechanisms may also be involved. However, further research, including in vivo studies and toxicity evaluations, is required.

New 5,6-dihydrobenzo[h]quinoline derivatives as potential demethylase inhibitors (DMIs): design, synthesis, activity evaluation and molecular dynamics simulation

BACKGROUND

Bipolaris maydis is a serious plant fungus and strongly affects the yield and quality of crops. The main control strategy is the employment of fungicides. To research efficient fungicide with novel structure, a series of novel 5,6-dihydrobenzo[h]quinoline derivatives were designed and synthesized.

RESULTS

Thirty-six novel 5,6-dihydrobenzo[h]quinoline analogues were designed and synthesized. The assay results showed that most compounds exhibited significant fungicidal activity against Pyricularia oryzae, Bipolaris maydis, Sclerotinia sclerotiorum, Penicillium digitatum and Valsa mali at 16 μg mL-1. Compounds 4 h, 5e, 6a and 6b showed better antifungal activity than fluquinconazole against B. maydis. Their half maximal effective concentration (EC50) values were 0.732, 0.283, 0.529, 0.644 and 0.826 μg mL-1, respectively. Furthermore, the bioactive compounds were determined against sterol 14α-demethylase (CYP51). The results indicated that they displayed prominent inhibiting activities, 4 h, 5e, 6a and 6b also had better inhibitory activities than fluquinconazole against CYP51. Their half maximal inhibitory concentration (IC50) values were 0.840, 0.315, 0.601, 0.750 and 1.018 μg mL-1, respectively. The fluorescent quenching tests of proteins indicated that the quenching patterns of compounds 5e and 6a were analogous to fluquinconazole. The molecular dynamics (MD) simulations indicated that compound 5e possessed stronger affinity than fluquinconazole to CYP51.

CONCLUSION

The results of the present study displayed that novel 5,6-dihydrobenzo[h]quinoline derivatives could be one scaffold of potential CYP51 inhibitor and will provide some valuable information for the research and development of new fungicides. © 2024 Society of Chemical Industry.

Discovery of novel azole derivatives with benzanilide-containing hydrophobic side chains for the treatment of drug-resistant fungal infections

As fungal resistance to existing antifungal drugs continues to rise, there is an urgent need for new drugs with anti-resistance activity. In this study, a series of newly designed and synthesized benzanilide-containing azoles exhibited promising antifungal activity against fluconazole-sensitive Candida albicans. Importantly, the newly synthesized compounds also displayed potent activity against azole-resistant strains, surpassing the performance of the positive control fluconazole. This suggests that these compounds may have the potential to combat drug-resistant fungal infections. Subsequent studies on the antifungal mechanisms revealed that the compound can inhibit fungal CYP51, thereby blocking ergosterol biosynthesis. Morphological observations of fungal cells further confirmed CYP51 as the target of action. Resistance mechanisms elucidated that these compounds can inhibit biofilm formation and the expression of resistance-related genes ERG11 and efflux pump gene CDR1, thereby reversing resistance. Meanwhile, the most potent compound A11 demonstrated the ability to stimulate reactive oxygen species, thereby exhibiting potent fungicidal activity. Furthermore, the compound A11 also showed good stability in liver microsomes and plasma metabolism. Cytotoxicity studies demonstrated low toxicity of the compounds against MRC-5 cells, indicating their potential safety for therapeutic use. In vivo experimental results indicated that the representative compound A11 significantly inhibited fungal infections caused by resistant strains. Molecular docking studies further supported the efficacy of compound A11, showing its ability to bind to Candida albicans CYP51. These findings highlight the promising antifungal activity and minimal cytotoxicity of the benzanilide-containing azoles, making them potential candidates for the treatment of drug-resistant fungal infections.

A quantitative analysis of ligand binding at the protein-lipid bilayer interface

The majority of drugs target membrane proteins, and many of these proteins contain ligand binding sites embedded within the lipid bilayer. However, targeting these therapeutically relevant sites is hindered by limited characterization of both the sites and the molecules that bind to them. Here, we introduce the Lipid-Interacting LigAnd Complexes Database (LILAC-DB), a curated dataset of 413 structures of ligands bound at the protein-bilayer interface. Analysis of these structures reveals that ligands binding to lipid-exposed sites exhibit distinct chemical properties, such as higher calculated partition coefficient (clogP), molecular weight, and a greater number of halogen atoms, compared to ligands that bind to soluble proteins. Additionally, we demonstrate that the atomic properties of these ligands vary significantly depending on their depth within and exposure to the lipid bilayer. We also find that ligand binding sites exposed to the bilayer have distinct amino acid compositions compared to other protein regions, which may aid in the identification of lipid-exposed binding sites. This analysis provides valuable guidelines for researchers pursuing structure-based drug discovery targeting underexploited ligand binding sites at the protein-lipid bilayer interface.

Antimicrobial Investigation of Phthalimide and N-Phthaloylglycine Esters: Activity, Mechanism of Action, Synergism and Ecotoxicity

Motivated by the search for novel antimicrobials against opportunistic resistant pathogens and based on the reported antimicrobial activity of phthalimides, two series of phthalimide and N-phthaloylglycine esters were designed to investigate whether the addition of butyl and aryl groups enhances their antimicrobial properties. Thus, in vitro antimicrobial activity, antifungal mechanism of action, effect combined with Chloramphenicol, in silico/vitro toxicity, and a docking molecular were studied. Phthalimide and N-phthaloylglycine aryl esters were obtained in yields of 75-98%. Phthalimide aryl ester 3b (R = Me) showed the best results against Gram-(+) and Gram-(-) bacteria, S. aureus and P. aeruginosa, respectively, and yeast fungi, C. tropicalis and C. albicans, with MIC values equal to 128 µg·mL-1. Regarding the antifungal mechanism of action on C. albicans, the MIC values of compound 3b changed from 128 to 1024 µg·mL-1 in the presence of ergosterol. Furthermore, compound 3b showed synergy with Chloramphenicol against P. aeruginosa, with a FICI value equal to 0.5. Finally, the four most promising compounds had their in silico/vitro toxicity evaluated, which showed moderate toxicity to non-toxicity on Artemia salina larvae. With the exception of Chloramphenicol, all selected compounds, including Fluconazole, are potentially hepatotoxic, but they were predicted not to cause skin sensitization, suggesting a potential application for topical use. Molecular docking revealed that compound 3b exhibits superior binding affinity and stability with the 50S ribosomal subunit (-92.69 kcal·mol-1) compared to Chloramphenicol, and a unique π-sulfur interaction with CYP51, suggesting its potential as a dual-action antibacterial and antifungal candidate against resistant pathogens.

In silico activity and effect of synthetic chalcones on Candida albicans and Candida tropicalis biofilms

Biofilm formation is considered one of the most important virulence factors for Candida species, which presents an extracellular matrix of polymeric substances that limits the passage of antifungals, leading to fungal resistance. Therefore, the present study investigated the biofilm eradication effect of synthetic chalcones against Candida albicans and Candida tropicalis. Molecular docking studies were conducted to verify the mechanism of action of chalcones on Candida species proteins. The biofilm eradication effect was determined using crystal violet methodology to quantify biomass and Thiazolyl blue tetrazolium bromide (MTT) to verify the influence on metabolic activity. A molecular docking study was also carried out with Candida proteins using the Protein Data Bank repository (https://www.rcsb.org/) and Autodocktools™ software. The results showed that (1E,4E)-1,5-diphenylpenta-1,4-dien-3-one (DB-Acetone), (1E,3E,6E,8E)-1,9-diphenylnona-1,3,6,8-tetraen-5-one (DB-CNM), and (1E,4E)-1,5-bis(4-methoxyphenyl)penta-1,4-dien-3-one (DB-Anisal) were able to eradicate the biomass of C. albicans CA INCQS 40006 (ATCC 10231), while fluconazole only reduced the biomass at the three tested concentrations (IC50, IC50 × 10, and IC50 × 20) against C. tropicalis CT INCQS 40042 (ATCC 13803). Both chalcones and fluconazole successfully reduced metabolic activity across all tested strains. The molecular docking study concluded that DB-Acetone, DB-Anisal, and DB-CNM exhibited significant affinity energy values toward the binding sites of C. albicans and C. tropicalis. It is concluded that the synthetic chalcones showed promising results in inhibiting Candida spp. biofilm, demonstrating efficacy in reducing biomass as well as metabolic activity.

Azole resistance: insights from Y132 substitutions in Candida sterol 14α-demethylase utilizing molecular dynamics simulations

Azole-resistant Candida infections are on the rise. Resistant substitutions at Y132 in sterol 14α-demethylase, the key target of azole drugs, are frequent. However, it is unclear why only some Y132 substitutions are favoured or how they exert differential effects on different azoles. Reported instances of Y132 substitutions were collected from the literature. Extensive molecular dynamics simulations of sterol 14α-demethylase bound to fluconazole or VT1161 (VT1) were performed using GROMACS, and the ligand-binding free energies were computed to quantify the effects of various Y132 substitutions on azole binding/interactions. Three azole-resistant substitutions, Y to C/F/H, were reported at residue position 132 in sterol 14α-demethylase. The Y132H was the most common substitution in C. albicans, while it was Y132F in other species. Ligand-binding free energies were -13.97 kcal/mol and -35.30 kcal/mol for fluconazole and VT1, respectively. There were differences in the ligand-binding free energies after substitutions compared to the wild type protein. Y132F and Y132H were the most frequent substitutions in Candida sterol 14α-demethylase. Far higher binding free energy of fluconazole in comparison with VT1 might partly explain its susceptibility to azole-resistant substitutions. The results give key insights into azole resistance, and antifungal drug discovery and optimization.

Exploring medium and long arm extensions of 1,2,4-triazole derivatives as Candida albicans 14α-demethylase (CYP51) inhibitors

Fungal infections have been described as a silent crisis affecting more than one billion people each year. At least 150 million of these cases involve severe and life threatening invasive fungal infections, accounting for approximately 1.7 million deaths annually. 1,2,4-Trizoles such as fluconazole and posaconazole are widely used antifungal agents, but azole resistance is an increasing problem requiring further study. 1,2,4-Triazole derivatives with medium and long arm extensions designed to bind within the Candida albicans CYP51 (CaCYP51) access channel were synthesised to study their inhibition of CaCYP51 (IC50, MIC) and binding affinity (K d). A long arm extension using the amide linker was found to be most effective (e.g.13), giving an antifungal profile vs. wild-type and resistant model fungal strains comparable with posaconazole.

Identifying novel inhibitors against drug-resistant mutant CYP-51 Candida albicans: A computational study to combat fungal infections

Candida albicans (C. albicans) is an opportunistic pathogen in immunocompromised individuals and a normal inhabitant of the oral cavity, throat, gastrointestinal tract, and genitourinary system among health populations. Our study focused on identifying new inhibitors capable of binding to the mutant cytochrome P450 family 51 (CYP-51) protein and intended to be effective against resistant C. albicans infections. The pharmacophore ligand-based model was used for the virtual screening of compound libraries. Molecular docking was performed on Maestro, Schrodinger. ADMET analysis was performed to check drug-likeness properties. Density function theory (DFT) calculations, molecular dynamic (MD) simulation, and free binding energy (MMPBSA) were also calculated. For docking, six compounds were selected from 11,022 hits from PubChem libraries, which showed the best interaction with mutant CYP-51 and were identified by pharmacophore mapping performed with the Pharma IT tool. Each of the six compounds was docked into the active site of the mutant CYP-51 protein. Overall, CP-3 exhibited significant binding affinity (-10.70 kcal/mol) as well as, showed good ADMET characteristics such as drug-likeness, absorption, distribution, metabolism, excretion, and toxicity. The lead compound, CP-3, was further used for MD simulation to observe the dynamic behavior of the complex in the active site of the mutant CYP-51 protein. Computational studies indicated that CP-3 could be a useful antagonist for the mutant protein, CYP-51. This study used computational approaches to identify potential inhibitors of C. albicans by targeting CYP-51 for antifungal drug development. Further invitro and in vivo studies are needed to evaluate its pharmacokinetic properties and efficacy as a novel antifungal drug.

Repurposing eugenol and cinnamaldehyde as potent antimicrobial agents: A comprehensive in-vitro and in-silico study

Multi-drug-resistant (MDR) pathogens represent a critical global health threat, necessitating the development of novel antimicrobial agents with broad-spectrum activity and minimal toxicity. This study investigates the antimicrobial and anti-biofilm properties of 4-Allyl-2-methoxyphenol (eugenol, EU) and (E)-3-Phenylprop-2-enal (cinnamaldehyde, CN) against 19 clinically significant pathogens through a combination of in-vitro assays and in-silico analyses. EU displayed remarkable activity, particularly against Aspergillus niger (20.5 ± 0.5 mm), and strong binding affinities with key protein targets, including peptide deformylase and β-carbonic anhydrase, with binding free energies (ΔG) ranging from -12.75 to -0.60 kcal/mol. CN exhibited exceptional activity against Staphylococcus epidermidis (29.6 ± 0.4 mm) and Candida albicans (36.6 ± 0.4 mm), supported by a significant binding affinity with β-carbonic anhydrase (ΔG: -5.23 kcal/mol). Dissociation constants (Kd) derived from MM-GBSA analyses indicated EU's strong inhibitory potential with nano- to picomolar Kd values, directly correlating with low IC50 values. CN demonstrated moderate inhibitory activity with Kd in the micromolar range. Molecular dynamics (MD) simulations confirmed the stability of these protein-ligand complexes, revealing critical hydrophobic interactions, such as those involving PHE122, that contributed to binding stabilization. ADMET profiling further underscored the favorable pharmacokinetics and safety of both compounds. These findings establish EU and CN as promising candidates for antimicrobial therapy, with potential applications in combating MDR pathogens and biofilm-associated infections. The complementary strengths of EU and CN warrant further structural optimization and combination studies, offering new avenues in the development of next-generation antimicrobial agents.

Itraconazole resistance in Madurella fahalii linked to a distinct homolog of the gene encoding cytochrome P450 14-α sterol demethylase (CYP51)

BACKGROUND

Mycetoma is a deep fungal infection caused by several microorganisms, with Madurella mycetomatis being the most common causative agent. Another related species, Madurella fahalii, is also known to cause eumycetoma. However, unlike M. mycetomatis, M. fahalii exhibits resistance to itraconazole, the standard treatment for eumycetoma, and the underlying cause of this resistance remains unknown. Therefore, understanding the mechanism of this resistance is critical for developing more effective therapies.

PRINCIPAL FINDINGS

Using the high-quality draft genome sequence of Madurella fahalii IFM 68171, we identified two copies of the gene encoding cytochrome P450 14-α sterol demethylase (CYP51), the target enzyme of itraconazole. These include a gene conserved among Madurella species (Mfcyp51A1) and a M. fahalii-specific gene (Mfcyp51A2). Both genes are actively transcribed in M. fahalii and are upregulated in response to itraconazole. Furthermore, heterologous expression in Saccharomyces cerevisiae revealed that transformants carrying the Mfcyp51A2 gene exhibited reduced susceptibility to itraconazole compared to those with Mfcyp51A1.

CONCLUSION

We demonstrated that itraconazole resistance in M. fahalii may be attributed to the presence of an additional CYP51 gene. This study represents the first report on the physiological characteristics of Madurella species using genetic engineering techniques.

Antimicrobial and antiparasitic potential of lupeol: antifungal effect on the Candida parapsilosis species complex and nematicidal activity against Caenorhabditis elegans

Introduction. There is growing concern about infections caused by non-albicans Candida species, including species of the Candida parapsilosis complex - which have seen a considerable increase in cases during the COVID-19 pandemic - in addition to concern about nematode resistance to currently used anthelmintics.Gap Statement. Lupeol is a triterpenoid phytosterol that has a wide range of biological activities, although its antifungal and antiparasitic potential is still poorly explored. Additionally, its effect on the biofilm of the C. parapsilosis species complex has not yet been studied.Aim. This study aimed to investigate the antifungal effect of lupeol against C. parapsilosis complex species, in planktonic cells and mature biofilms, as well as its nematicidal potential against Caenorhabditis elegans. In addition, molecular docking was performed to identify potential target molecules for lupeol's antifungal effect.Methodology. Twelve strains of C. parapsilosis species complex were used. Planktonic susceptibility was performed through the broth microdilution assay, while the antibiofilm effect was investigated by measuring the biomass and metabolic activity. The antifungal mechanism of action of lupeol was investigated by target fishing. The evaluation of the nematicidal effect was performed using the C. elegans infection model.Results. Lupeol demonstrated antifungal activity against planktonic cells with a MIC between 64 and 512 µg ml-1. In mature biofilms, lupeol was able to reduce biomass starting from a concentration of 1024 µg ml-1 and reduce metabolic activity from a concentration of 64 µg ml-1. It was observed that there was interaction of lupeol with the enzyme 14α-demethylase. Furthermore, lupeol had a nematicidal effect from a concentration of 64 µg ml-1.Conclusion. Lupeol exhibits an antifungal effect on the C. parapsilosis species complex, in the planktonic and mature biofilm forms, possibly by affecting the ergosterol synthesis. Lupeol further demonstrated a nematicidal potential.

QSAR, Antimicrobial, and Antiproliferative Study of (R/S)-2-Thioxo-3,4-dihydropyrimidine-5-carboxanilides

Owing to the significant contribution of three-dimensional (3D) field-based QSAR toward hit optimization and accurately predicting the activities of small molecules, herein, the 3D-QSAR, in vitro antimicrobial, molecular docking, and pharmacophore modeling studies of all the isolated (R/S)-2-thioxo-DHPM-5-carboxanilides exhibiting antimicrobial activity were carried out. The screening process was performed using 46 compounds, and the best-scoring model with the top statistical values was considered for bacterial and fungal targets Bacillus subtilis and Candida albicans. As a result of 3D-QSAR analysis, compound 4v-(S)- and 4v-(R)-isomers were found to be more potent compared to the standard drugs tetracycline and fluconazole, respectively. Furthermore, the enantiomerically pure isomers 4q, 4d', 4n, 4f', 4v, 4q', 4c, and 4p' were found to be more potent than tetracycline and fluconazole to inhibit the bacterial and fungal growth against B. subtilis, Salinivibrio proteolyticus, C. albicans, and Aspergillus niger, respectively. Molecular docking analysis shows that with the glide score of -10.261 kcal/mol, 4v-(R)-isomer was found to be more potent against the fungal target C. albicans and may target the 14-α demethylase than fluconazole. Furthermore, all compounds' antiproliferative activity results showed that 4o' exhibited GI50 values between 8.8 and 34 μM against six solid tumor cell lines. Following the greater potential of 4o' toward the HeLa cell line, its kinetics study and live cell imaging were carried out. These outcomes highlight the acceptance and safety as well as the potential of compounds as effective antiproliferative and antifungal agents.

The fluoroquinolone compounds potentiate the antifungal activity of the echinocandins against Aspergillus fumigatus

The antifungal drugs of the echinocandin family show high efficacy against Aspergillus fumigatus. However, their paradoxical effect, which restores fungal growth at high drug concentrations, and the emergence of resistant strains necessitate improvements. We identified 13 fluoroquinolone compounds from a chemical library containing 10,000 compounds that potentiate the antifungal activity of caspofungin. Among them, NE-E07 significantly enhanced the efficacy of echinocandins against A. fumigatus, including resistant strains, without potentiating other antifungal families like voriconazole or amphotericin B. Specifically, NE-E07 demonstrated a unique ability to potentiate caspofungin's activity against the echinocandin-resistant strain USHM-M0051 isolated from patients. Our experiments revealed that NE-E07, in combination with caspofungin, affected ergosterol biosynthesis in a manner consistent with azole drugs. Docking tests suggest that NE-E07 has a high binding affinity with CYP51, which affects ergosterol biosynthesis similarly to azole drugs. Interestingly, known fluoroquinolones like ciprofloxacin, nalidixic acid, and norfloxacin did not show this potentiating effect, suggesting that NE-E07's unique structure is critical for its activity. Moreover, NE-E07 did not enhance echinocandin activity against Candida albicans or Cryptococcus neoformans, highlighting its specific action against A. fumigatus. In vivo studies demonstrated that co-treatment with NE-E07 and caspofungin increased the survival rate of mice infected with A. fumigatus. This significant improvement in survival underscores the potential clinical relevance of NE-E07 as a co-administered drug with echinocandins for treating fungal infections, particularly those resistant to echinocandins.

Preparation, Antifungal Activity Evaluation, and Mechanistic Studies of Unique and Structurally Novel Pyrazole-Heterocyclic-Amide Analogues

Thirty-six novel pyrazole-heterocyclic-amide analogues were designed, synthesized, and characterized. The bioassay results showed that most target compounds exhibited good fungicidal activities against Rhizoctonia solani, Gibberella zeae, Pseudoperonospora cubensis, Helminthosporium maydis, and Coniothyrium diplodiella at 20 μg/mL. Compounds 6d, 6f, 6l, and 6j possessed better fungicidal activities than the commercial fungicide prochloraz against H. maydis. Their half maximal effective concentration (EC50) values were 0.47, 0.26, 0.58, and 0.69 μg/mL, respectively, and the EC50 value of prochloraz was 0.77 μg/mL. Furthermore, the inhibitory activities for the bioactive compounds were determined against sterol 14α-demethylase (CYP51), the results displayed that they had prominent activities, compounds 6d, 6f, 6l, and 6j also showed better inhibitory activities than prochloraz against CYP51, their half maximal inhibitory concentration (IC50) values were 0.543, 0.29, 0.77, 0.66, and 0.86 μg/mL, respectively. The results of molecular dynamics simulations exhibited that compound 6f displayed stronger affinity to CYP51 than prochloraz, and estimated ΔGbind values of -44.9 and -37.2 kcal/mol were found for 6f and prochloraz, respectively.

Retinoids as Alternative Antifungal Agents Against Candida albicans: In Vitro and In Silico Evidence

Candida albicans (C. albicans) is the most common pathogen responsible for a wide spectrum of human infections ranging from superficial mucocutaneous mycoses to systemic life-threatening diseases. Its main virulence factors are the morphological transition between yeast and hyphal forms and the ability to produce biofilm. Novel antifungal strategies are required given the severity of systemic candidiasis, especially in immunocompromised patients, and the lack of effective anti-biofilm treatments. We previously demonstrated that all-trans retinoic acid (ATRA), an active metabolite of vitamin A, exerted an inhibitory effect on Candida growth, yeast-hyphal transition and biofilm formation. Here, we further investigated the possible anti-Candida potential of trifarotene and tazarotene, which are the other two molecules belonging to the retinoid family, compared to ATRA. The results indicate that both drugs were able to suppress Candida growth, germination and biofilm production, although trifarotene was proven to be more effective than tazarotene, showing effectiveness comparable to ATRA. In silico studies suggest that all three retinoids may exert antifungal activity through their molecular interactions with the heat shock protein (Hsp) 90 and 14α-demethylase of C. albicans. Moreover, interactions between retinoids and ergosterol have been observed, suggesting that those compounds have great potential against C. albicans infections.

Synthesis and Evaluation of Antibacterial and Antifungal Activities In vitro and In silico of Novel Morpholinoalkoxychalcones

INTRODUCTION

Chalcone compounds exhibit diverse bioactivities, attracting significant interest. Morpholine is a heterocycle commonly used in medicinal chemistry. It could enhance the potency, pharmacokinetics, and bioactivities of its compounds.

METHODS

Adding morpholine into the chalcone scaffold could help create new compounds with favorable bioactivities. In this study, a new parallel synthesis procedure has been developed. Using this procedure, 18 novel morpholinoalkoxychalcones have been successfully synthesized. They had chains with morpholine appended on ring A or ring B. All the synthesized compounds were evaluated for the antibacterial and antifungal activities by agar diffusion method on 5 bacteria and 2 fungi strains.

RESULTS

The compounds with good inhibition were determined with respect to the MIC values by the agar dilution method. Among the tested compounds, B.21 was found to be the best against E. faecalis, with an MIC value of 0.6 mM. B.43 with an MIC value of 2.04 mM has displayed its potential in inhibiting A. niger and C. albicans the best among other compounds.

CONCLUSION

The in silico study has revealed two targets to align with the in vitro results. Longer alkyl chains have enhanced the activity, along with the presence of OH, NH2, and halogen groups on both rings A and B.

Identification of novel and potent triazoles targeting CYP51 for antifungal: Design, synthesis, and biological study

Invasive fungal infections (IFIs) are emerging as a serious infectious disease worldwide. Due to the lack of effective antifungal drugs and serious drug resistance, the number of people with low immunity is increasing, leading to high morbidity and mortality. Azole drugs targeting CYP51 are widely used in the treatment of invasive fungal infections. By analyzing representative azole antifungal drugs, the characteristics of pharmacophore were summarized. The binding mode of lead compound Iodiconazole was analyzed, and it was found that the narrow hydrophobic cavity was not fully occupied. Therefore, a series of triazole compounds were designed and synthesized by fragment growth strategy. Most of the compounds showed strong inhibitory activity against pathogenic fungi, among which compound A33 showed excellent inhibitory activity against pathogenic fungi and drug-resistant strains. In addition, the preferred compound A33 can prevent fungal phase transition, the formation of fungal biofilm, and show satisfactory fungicidal activity. In addition, the compound A33 was almost non-toxic to mammalian HUVEC cell. These results strongly suggested that compound A33 was worth further investigation as a potential azole inhibitor.

Synthesis, characterization, biological activities, and computational studies of pyrazolyl-thiazole derivatives of thiophene

This study reports the synthesis, characterization, and biological evaluation of a series of pyrazolyl-thiazole derivatives of thiophene. Seven compounds were synthesized and characterized using NMR spectroscopy and mass spectrometry. The antimicrobial activities of these derivatives were evaluated against various bacterial (Escherichia coli, Bacillus subtilis, Bacillus megaterium, Staphylococcus aureus) and fungal strains (Aspergillus niger, Aspergillus oryzae, Rhizopus, Candida albicans), demonstrating significant inhibition zones and low minimum inhibitory concentrations (MIC). In addition, the compounds exhibited notable antioxidant activities in DPPH and hydroxyl radical scavenging assays. Computational studies, including density functional theory (DFT) calculations and molecular docking simulations, were performed to understand the electronic properties and binding interactions of the synthesized compounds with biological targets. The molecular docking results supported the experimental findings, highlighting the potential of these pyrazolyl-thiazole derivatives as multifunctional therapeutic agents with both antimicrobial and antioxidant properties.

New Ester-Containing Azole Derivatives With Potent Anti-Candida Effects: Synthesis, Antifungal Susceptibility, Cytotoxicity, and Molecular Modeling Studies

Mortalities due to mycoses have dramatically increased with the emergence of drug-resistant strains and growing immune-compromised populations globally. Azole antifungals have been the first choice against fungal infections of a wide spectrum and several azole derivatives with ester function were reported for their potentially promising and favorable activity against Candida spp. In this study, we designed and synthesized a series of 1-(aryl)-2-(1H-imidazol-1-yl/1H-1,2,4-triazol-1-yl)ethyl esters, and tested them against seven reference Candida strains using EUCAST reference microdilution method. Among the series, 6a, 6d, and 6g proved highly potent in vitro compared to fluconazole; especially against Candida albicans and Candida tropicalis with minimum inhibitor concentration (MIC) values as low as 0.125 and 0.06 mg/L, respectively, although their activities against Candida krusei and Candida glabrata remained limited. The compounds also showed minimal toxicity to murine fibroblasts according to the in vitro cytotoxicity tests. Molecular modeling predicted 6g as an orally available druglike compound according to all parameters and CYP51 inhibition as the likely mechanism for their antifungal effects. The study underpins the promise of azoles with ester functionality as a potential scaffold for small-molecule antifungal drug design.

Cytochrome P450 monooxygenase systems: Diversity and plasticity for adaptive stress response

Superfamily of cytochromes P450 (CYPs) is composed of heme-thiolate-containing monooxygenase enzymes, which play crucial roles in the biosynthesis, bioactivation, and detoxification of a variety of organic compounds, both endogenic and exogenic. Majority of CYP monooxygenase systems are multi-component and contain various redox partners, cofactors and auxiliary proteins, which contribute to their diversity in both prokaryotes and eukaryotes. Recent progress in bioinformatics and computational biology approaches make it possible to undertake whole-genome and phylogenetic analyses of CYPomes of a variety of organisms. Considerable variations in sequences within and between CYP families and high similarity in secondary and tertiary structures between all CYPs along with dramatic conformational changes in secondary structure elements of a substrate binding site during catalysis have been reported. This provides structural plasticity and substrate promiscuity, which underlie functional diversity of CYPs. Gene duplication and mutation events underlie CYP evolutionary diversity and emergence of novel selectable functions, which provide the involvement of CYPs in high adaptability to changing environmental conditions and dietary restrictions. In our review, we discuss the recent advancements and challenges in the elucidating the evolutionary origin and mechanisms underlying the CYP monooxygenase system diversity and plasticity. Our review is in the view of hypothesis that diversity of CYP monooxygenase systems is translated into the broad metabolic profiles, and this has been acquired during the long evolutionary time to provide structural plasticity leading to high adaptative capabilities to environmental stress conditions.

Most azole resistance mutations in the Candida albicans drug target confer cross-resistance without intrinsic fitness cost

Azole antifungals are the main drugs used to treat fungal infections. Amino acid substitutions in the drug target Erg11 (Cyp51) are a common resistance mechanism in pathogenic yeasts. How many and which mutations confer resistance is, however, largely unknown. Here we measure the impact of nearly 4,000 amino acid variants of Candida albicans Erg11 on the susceptibility to six clinical azoles. This was achieved by deep mutational scanning of CaErg11 expressed in Saccharomyces cerevisiae. We find that a large fraction of mutations lead to resistance (33%), most resistance mutations confer cross-resistance (88%) and only a handful of resistance mutations show a significant fitness cost (9%). Our results reveal that resistance to azoles can arise through a large set of mutations and this will probably lead to azole pan-resistance, with little evolutionary compromise. This resource will help inform treatment choices in clinical settings and guide the development of new drugs.

Investigating role of positively selected genes and mutation sites of ERG11 in drug resistance of Candida albicans

The steep increase in acquired drug resistance in Candida isolates has posed a great challenge in the clinical management of candidiasis globally. Information of genes and codon sites that are positively selected during evolution can provide insights into the mechanisms driving antifungal resistance in Candida. This study aimed to create a manually curated list of genes of Candida spp. reported to be associated with antifungal resistance in literature, and further investigate the structure-function implications of positively selected genes and mutation sites. Sequence analysis of antifungal drug resistance associated gene sequences from various species and strains of Candida revealed that ERG11 and MRR1 of C. albicans were positively selected during evolution. Four sites in ERG11 and two sites in MRR1 of C. albicans were positively selected and associated with drug resistance. These four sites (132, 405, 450, and 464) of ERG11 are predictive markers for azole resistance and have evolved over time. A well-characterized crystal structure of sterol-14-α-demethylase (CYP51) encoded by ERG11 is available in PDB. Therefore, the stability of CYP51 in complex with fluconazole was evaluated using MD simulations and molecular docking studies for two mutations (Y132F and Y132H) reported to be associated with azole resistance in literature. These mutations induced high flexibility in functional motifs of CYP51. It was also observed that residues such as I304, G308, and I379 of CYP51 play a critical role in fluconazole binding affinity. The insights gained from this study can further guide drug design strategies addressing antimicrobial resistance.

Imidazoles and Quaternary Ammonium Compounds as Effective Therapies against (Multidrug-Resistant) Bacterial Wound Infections

BACKGROUND/OBJECTIVES

The rise and spread of antimicrobial resistance complicates the treatment of bacterial wound pathogens, further increasing the need for newer, effective therapies. Azoles such as miconazole have shown promise as antibacterial compounds; however, they are currently only used as antifungals. Previous research has shown that combining azoles with quaternary ammonium compounds yields synergistic activity against fungal pathogens, but the effect on bacterial pathogens has not been studied yet.

METHODS

In this study, the focus was on finding active synergistic combinations of imidazoles and quaternary ammonium compounds against (multidrug-resistant) bacterial pathogens through checkerboard assays. Experimental evolution in liquid culture was used to evaluate the possible emergence of resistance against the most active synergistic combination.

RESULTS

Several promising synergistic combinations were identified against an array of Gram-positive pathogens: miconazole/domiphen bromide, ketoconazole/domiphen bromide, clotrimazole/domiphen bromide, fluconazole/domiphen bromide and miconazole/benzalkonium chloride. Especially, miconazole with domiphen bromide exhibits potential, as it has activity at a low concentration against a broad range of pathogens and shows an absence of strong resistance development over 11 cycles of evolution.

CONCLUSIONS

This study provides valuable insight into the possible combinations of imidazoles and quaternary ammonium compounds that could be repurposed for (topical) wound treatment. Miconazole with domiphen bromide shows the highest application potential as a possible future wound therapy. However, further research is needed into the mode of action of these compounds and their efficacy and toxicity in vivo.

Exploring Triazole-Connected Steroid-Pyrimidine Hybrids: Synthesis, Spectroscopic Characterization, and Biological Assessment

Molecules originating from natural sources are physicochemically and biologically diverse. The conjugation of two active biomolecules has become the foundation for medical and pharmaceutical sciences. An effective synthesis of 11 new steroid-pyrimidine conjugates containing 1,2,3-triazole rings was carried out. The group of 3α-OH bile acids (lithocholic, deoxycholic, cholic) and 3β-OH sterols (cholesterol, cholestanol) were respectively modified to azidoacetates. 2-thiouracil was converted into N(1)S and N(3)S dipropargyl derivatives. Azide-alkyne cycloaddition in the presence of copper(I) of the obtained compounds led to the preparation of 1,2,3-triazole derivatives. Based on a series of spectroscopic (1H NMR, 13C NMR, Fourier-transform infrared (FT-IR)), spectrometric analyses (Electrospray ionization-mass spectrometry (ESI-MS), electron impact-mass spectrometry (EI-MS)), and semiempirical calculations, the structures of all compounds were confirmed. In silico biological tests and molecular docking (for domain 1KZN, 2H94, 5V5Z, 1EZF, 2Q85) were performed for selected compounds. The tests performed indicate the theoretical antimicrobial potential of the obtained ligands.

Chiral Fluorescent Antifungal Azole Probes Detect Resistance, Uptake Dynamics, and Subcellular Distribution in Candida Species

Azoles are essential for fungal infection treatment, yet the increasing resistance highlights the need for innovative diagnostic tools and strategies to revitalize this class of antifungals. We developed two enantiomers of a fluorescent antifungal azole probe (1 S and 1 R ), analyzing 60 Candida strains via live-cell microscopy. A database of azole distribution images in strains of Candida albicans, Candida glabrata, and Candida parapsilosis, among the most important pathogenic Candida species, was established and analyzed. This analysis revealed distinct populations of yeast cells based on the correlation between fluorescent probe uptake and cell diameter. Varied uptake levels and subcellular distribution patterns were observed in C. albicans, C. glabrata, and C. parapsilosis, with the latter displaying increased localization to lipid droplets. Comparison of the more potent fluorescent antifungal azole probe enantiomer 1 S with the moderately potent enantiomer 1 R highlighted time-dependent differences in the uptake profiles. The former displayed a marked elevation in uptake after approximately 150 min, indicating the time required for significant cell permeabilization to occur and its association with the azole's antifungal activity potency. Divergent uptake levels between susceptible and high efflux-based azole-resistant strains were detected, offering a rapid diagnostic approach for identifying azole resistance. This study highlights unique insights achievable through fluorescent antifungal azole probes, unraveling the complexities of azole resistance, subcellular dynamics, and uptake within fungal pathogens.

A First-in-Class Pyrazole-isoxazole Enhanced Antifungal Activity of Voriconazole: Synergy Studies in an Azole-Resistant Candida albicans Strain, Computational Investigation and in Vivo Validation in a Galleria mellonella Fungal Infection Model

The widespread and irrational use of azole antifungal agents has led to an increase of azole-resistant Candida albicans strains with an urgent need for combination drug therapy, enhancing the treatment efficacy. Here, we report the discovery of a first-in-class pyrazole-isoxazole, namely, 5b, that showed remarkable growth inhibition against the C. albicans ATCC 10231 strain in combination with voriconazole, acting as a downregulator of ERG 11 (Cyp51) gene expression with a significant reduction of the yeast-to-hypha morphological transition. Furthermore, C. albicans CYP51 enzyme assay and in-depth molecular docking studies unveiled the unique ability of the combination of 5b and voriconazole to completely fill the CYP51 binding sites. In vivo studies using a Galleria mellonella model confirmed the previously in vitro observed synergistic effect of 5b with voriconazole. Also considering its biocompatibility in a cellular model of human keratinocytes, these results indicate that 5b represents a promising compound for a further optimization campaign.

Design, Synthesis, and Activity Evaluation of Novel Benzazole Bifunctional Antifungal Inhibitors with an LDH Carrier

Fungal infections maintain a close relation with the body's immune function. In this study, three series of benzazole compounds were designed as dual-target (PD-L1/CYP51) inhibitors using the skeleton splicing approach; their molecular structures were synthesized and evaluated accordingly. Among them, the compounds 9a-2, 12a-2, and 12b-1 exhibited potent antifungal activity and dual-target inhibition ability. Especially, the compound 12a-2 simultaneously exerted excellent bifunctional effects of fungal inhibition and immune activation. Moreover, a layered double hydroxide (LDH) carrier was also successfully constructed based on an infection microenvironment to improve the bioavailability and the targeting of compound 12a-2. This significantly accelerated the recovery process of deep and shallow fungal infections. In conclusion, this study expanded the development horizon of antifungal drugs and provided a novel drug delivery route for treating fungal infections.

Antifungal Activity, Mode of Action, and Cytotoxicity of 4-Chlorobenzyl p-Coumarate: A Promising New Molecule

Fungal infections represent a serious health problem worldwide. The study evaluated the antifungal activity of 4-chlorobenzyl p-coumarate, an unprecedented semi-synthetic molecule. Docking molecular and assay experiments were conducted to determine the Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC), mode of action, effect on growth, fungal death kinetics, drug association, effects on biofilm, micromorphology, and against human keratinocytes. The investigation included 16 strains of Candida spp, including C. albicans, C. krusei, C. glabrata, C. tropicalis, C. dubliniensis, C. lusitaniae, C. utilis, C. rugosa, C. guilhermondi, and C. parapsilosis. Docking analysis predicted affinity between the molecule and all tested targets. MIC and MFC values ranged from 3.9 μg/mL (13.54 μM) to 62.5 μg/mL (217.01 μM), indicating a probable effect on the plasma membrane. The molecule inhibited growth from the first hour of testing. Association with nystatin proved to be indifferent. All concentrations of the molecule reduced fungal biofilm. The compound altered fungal micromorphology. The tested compound exhibited an IC50 of 7.90±0.40 μg/mL (27.45±1.42 μM) for keratinocytes. 4-chlorobenzyl p-coumarate showed strong fungicidal effects, likely through its action on the plasma membrane and alteration of fungal micromorphology, and mildly cytotoxic to human keratinocytes.

Naringenin-Zinc Oxide Nanocomposites Amalgamated Polymeric Gel Augmented Drug Delivery and Attenuated Experimental Cutaneous Candidiasis in Balb/c Mice: In Vitro and In Vivo Studies

Naringenin (NRG) inhibits the fungal 17β-hydroxysteroid dehydrogenase accountable for ergosterol synthesis in Candida albicans (C. albicans), a causative agent for cutaneous candidiasis. In present research, NRG was complexed with ZnO nanomaterial (NRG-Zn2+) to synthesize NRG-Zn2+ nanocomposites. The particle size and ζ-potential of NRG-Zn2+ nanocomposites were respectively estimated to be 180.33 ± 1.22-nm and - 3.92 ± 0.35-mV. In silico data predicted the greater affinity of NRG-Zn2+ nanocomposite for 14α-demethylase and ceramide in comparison to NRG alone. Later, NRG-Zn2+ nanocomposites solution was transformed in to naringenin-zinc oxide nanocomposites loaded chitosan gel (NRG-Zn-CS-Gel) with viscosity and firmness of 854806.7 ± 52386.43 cP and 698.27 ± 10.35 g, respectively. The ex-vivo skin permeation demonstrated 70.49 ± 5.22% skin retention, significantly greater (P < 0.05) than 44.48 ± 3.06% of naringenin loaded chitosan gel (NRG-CS-Gel) and 31.24 ± 3.28% of naringenin solution (NRG Solution). NRG-Zn-CS-Gel demonstrated 6.71 ± 0.84% permeation of NRG with a flux value of 0.046 ± 0.01-µg/cm2/h. The MIC50 of NRG-Zn-CS-Gel against C. albicans was estimated to be 0.156-µg/mL with FICI (fractional inhibitory concentration index) of 0.018 that consequently exhibited synergistic efficacy. Further, NRG-Zn-CS-Gel demonstrated superior antifungal efficacy in C. albicans induced cutaneous candidiasis infection in Balb/c mice. The fungal burden in NRG-Zn-CS-Gel treated group was 109 ± 25 CFU/mL, significantly lower (P < 0.05) than positive control (2260 ± 446 CFU/mL), naringenin loaded chitosan gel (NRG-CS-Gel; 928 ± 127 CFU/mL) and chitosan gel (CS-Gel; 2116 ± 186 CFU/mL) treated mice. Further, histopathology examination and cytokine profiling of TNF-α, IL-1β and IL-10 revealed the healing of skin and inflammation associated with cutaneous candidiasis infection. In conclusion, NRG-Zn-CS-Gel may be a potential candidate for translating in to a clinical viable topical nanotherapeutic.

Investigation of Azole Resistance Involving cyp51A and cyp51B Genes in Clinical Aspergillus flavus Isolates

This study aimed to investigate azole resistance mechanisms in Aspergillus flavus, which involve cyp51A and cyp51B genes. Real-time Reverse Transcriptase qPCR method was applied to determine the overexpression of cyp51A and cyp51B genes for 34 A. flavus isolates. PCR sequencing of these two genes was used to detect the presence of gene mutations. Susceptibility test found sensitivity to voriconazole (VOR) in all strains. 14.7% and 8.8% of isolates were resistant to itraconazole (IT) and posaconazole (POS), respectively, with a cross-resistance in 5.8%. For the double resistant isolates (IT/POS), the expression of cyp51A was up to 17-fold higher. PCR sequencing showed the presence of 2 mutations in cyp51A: a synonymous point mutation (P61P) in eight isolates, which did not affect the structure of CYP51A protein, and another non synonymous mutation (G206L) for only the TN-33 strain (cross IT/POS resistance) causing an amino acid change in the protein sequence. However, we noted in cyp51B the presence of the only non-synonymous mutation (L177G) causing a change in amino acids in the protein sequence for the TN-31 strain, which exhibits IT/POS cross-resistance. A short single intron of 67 bp was identified in the cyp51A gene, whereas three short introns of 54, 53, and 160 bp were identified in the cyp51B gene. According to the models provided by PatchDock software, the presence of non-synonymous mutations did not affect the interaction of CYP51A and CYP51B proteins with antifungals. In our study, the overexpression of the cyp51A and cyp51B genes is the primary mechanism responsible for resistance in A. flavus collection. Nevertheless, other resistance mechanisms can be involved.

Comparative Genomics of the First Resistant Candida auris Strain Isolated in Mexico: Phylogenomic and Pan-Genomic Analysis and Mutations Associated with Antifungal Resistance

Candida auris is an emerging multidrug-resistant and opportunistic pathogenic yeast. Whole-genome sequencing analysis has defined five major clades, each from a distinct geographic region. The current study aimed to examine the genome of the C. auris 20-1498 strain, which is the first isolate of this fungus identified in Mexico. Based on whole-genome sequencing, the draft genome was found to contain 70 contigs. It had a total genome size of 12.86 Mbp, an N50 value of 1.6 Mbp, and an average guanine-cytosine (GC) content of 45.5%. Genome annotation revealed a total of 5432 genes encoding 5515 proteins. According to the genomic analysis, the C. auris 20-1498 strain belongs to clade IV (containing strains endemic to South America). Of the two genes (ERG11 and FKS1) associated with drug resistance in C. auris, a mutation was detected in K143R, a gene located in a mutation hotspot of ERG11 (lanosterol 14-α-demethylase), an antifungal drug target. The focus on whole-genome sequencing and the identification of mutations linked to the drug resistance of fungi could lead to the discovery of new therapeutic targets and new antifungal compounds.

Novel Pyrido[4,3-d]pyrimidine Derivatives as Potential Sterol 14α-Demethylase Inhibitors: Design, Synthesis, Inhibitory Activity, and Molecular Modeling

Thirty-four new pyrido[4,3-d]pyrimidine analogs were designed, synthesized, and characterized. The crystal structures for compounds 2c and 4f were measured by means of X-ray diffraction of single crystals. The bioassay results showed that most target compounds exhibited good fungicidal activities against Pyricularia oryzae, Rhizoctonia cerealis, Sclerotinia sclerotiorum, Botrytis cinerea, and Penicillium italicum at 16 μg/mL. Compounds 2l, 2m, 4f, and 4g possessed better fungicidal activities than the commercial fungicide epoxiconazole against B. cinerea. Their half maximal effective concentration (EC50) values were 0.191, 0.487, 0.369, 0.586, and 0.670 μg/mL, respectively. Furthermore, the inhibitory activities of the bioactive compounds were determined against sterol 14α-demethylase (CYP51). The results displayed that they had prominent activities. Compounds 2l, 2m, 4f, and 4g also showed better inhibitory activities than epoxiconazole against CYP51. Their half maximal inhibitory concentration (IC50) values were 0.219, 0.602, 0.422, 0.726, and 0.802 μg/mL, respectively. The results of molecular dynamics (MD) simulations exhibited that compounds 2l and 4f possessed a stronger affinity to CYP51 than epoxiconazole.

Construction and Activity Evaluation of Novel Bifunctional Inhibitors and a COF Carrier Based on a Fungal Infection Microenvironment

Faced with increasingly serious fungal infections and drug resistance issues, three different series of novel dual-target (programmed death ligand 1/14 α-demethylase) compounds were constructed through the fragment combination pathway in the study. Their chemical structures were synthesized, characterized, and evaluated. Among them, preferred compounds 10c-1, 17b-1, and 18b-2 could efficiently exert their antifungal and antidrug-resistant fungal ability through blocking ergosterol biosynthesis, inducing the upregulation of reactive oxygen species level, and triggering apoptosis. Especially, compound 18b-2 exhibited the synergistic function of fungal inhibition and immune activation. Moreover, the covalent organic framework carrier was also generated based on the acidic microenvironment of fungal infection to improve the bioavailability and targeting of preferred compounds; this finally accelerated the body's recovery rate.

Design, Synthesis, Bioactive Evaluation, and Molecular Dynamics Simulation of Novel 4H-Pyrano[3,2-c]pyridine Analogues as Potential Sterol 14α-Demethylase (CYP51) Inhibitors

To discover potential sterol 14α-demethylase (CYP51) inhibitors, thirty-four unreported 4H-pyrano[3,2-c]pyridine derivatives were designed and synthesized. The assay results indicated that most compounds displayed significant fungicidal activity against Sclerotinia sclerotiorum, Colletotrichum lagenarium, Botrytis cinerea, Penicillium digitatum, and Fusarium oxysporum at 16 μg/mL. The half maximal effective concentration (EC50) values of compounds 7a, 7b, and 7f against B. cinerea were 0.326, 0.530, and 0.610, respectively. Namely, they had better antifungal activity than epoxiconazole (EC50 = 0.670 μg/mL). Meanwhile, their half maximal inhibitory concentration (IC50) values against CYP51 were 0.377, 0.611, and 0.748 μg/mL, respectively, representing that they also possessed better inhibitory activities than epoxiconazole (IC50 = 0.802 μg/mL). The fluorescent quenching tests of proteins showed that 7a and 7b had similar quenching patterns to epoxiconazole. The molecular dynamics simulations indicated that the binding free energy of 7a and epoxiconazole to CYP51 was -35.4 and -27.6 kcal/mol, respectively.

Cytochrome P450 Enzymes as Drug Targets in Human Disease

Although the mention of cytochrome P450 (P450) inhibition usually brings to mind unwanted variability in pharmacokinetics, in several cases P450s are good targets for inhibition. These P450s are essential, but in certain disease states, it is desirable to reduce the concentrations of their products. Most of the attention to date has been with human P450s 5A1, 11A1, 11B1, 11B2, 17A1, 19A1, and 51A1. In some of those cases, there are multiple drugs in use, e.g., exemestane, letrozole, and anastrozole with P450 19A1, the steroid aromatase target in breast cancer. There are also several targets that are less developed, e.g., P450s 2A6, 8B1, 4A11, 24A1, 26A1, and 26B1. SIGNIFICANCE STATEMENT: The selective inhibition of certain cytochrome P450s that have major physiological functions has been shown to be very efficacious in certain human diseases. In several cases, the search for better drugs continues.

Multifunctional in vitro, in silico and DFT analyses on antimicrobial BagremycinA biosynthesized by Micromonospora chokoriensis CR3 from Hieracium canadense

Among the actinomycetes in the rare genera, Micromonospora is of great interest since it has been shown to produce novel therapeutic compounds. Particular emphasis is now on its isolation from plants since its population from soil has been extensively explored. The strain CR3 was isolated as an endophyte from the roots of Hieracium canadense, and it was identified as Micromonospora chokoriensis through 16S gene sequencing and phylogenetic analysis. The in-vitro analysis of its extract revealed it to be active against the clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and Candida tropicalis (15 mm). No bioactivity was observed against Gram-negative bacteria, Escherichia coli ATCC 25922, and Klebsiella pneumoniae ATCC 706003. The Micromonospora chokoriensis CR3 extract was also analyzed through the HPLC-DAD-UV-VIS resident database, and it gave a maximum match factor of 997.334 with the specialized metabolite BagremycinA (BagA). The in-silico analysis indicated that BagA strongly interacted with the active site residues of the sterol 14-α demethylase and thymidylate kinase enzymes, with the lowest binding energies of - 9.7 and - 8.3 kcal/mol, respectively. Furthermore, the normal mode analysis indicated that the interaction between these proteins and BagA was stable. The DFT quantum chemical properties depicted BagA to be reasonably reactive with a HOMO-LUMO gap of (ΔE) of 4.390 eV. BagA also passed the drug-likeness test with a synthetic accessibility score of 2.06, whereas Protox-II classified it as a class V toxicity compound with high LD50 of 2644 mg/kg. The current study reports an endophytic actinomycete, M. chokoriensis, associated with H. canadense producing the bioactive metabolite BagA with promising antimicrobial activity, which can be further modified and developed into a safe antimicrobial drug.

Identification of Potent and Selective Inhibitors of Acanthamoeba: Structural Insights into Sterol 14α-Demethylase as a Key Drug Target

Acanthamoeba are free-living pathogenic protozoa that cause blinding keratitis, disseminated infection, and granulomatous amebic encephalitis, which is generally fatal. The development of efficient and safe drugs is a critical unmet need. Acanthamoeba sterol 14α-demethylase (CYP51) is an essential enzyme of the sterol biosynthetic pathway. Repurposing antifungal azoles for amoebic infections has been reported, but their inhibitory effects on Acanthamoeba CYP51 enzymatic activity have not been studied. Here, we report catalytic properties, inhibition, and structural characterization of CYP51 from Acanthamoeba castellanii. The enzyme displays a 100-fold substrate preference for obtusifoliol over lanosterol, supporting the plant-like cycloartenol-based pathway in the pathogen. The strongest inhibition was observed with voriconazole (1 h IC50 0.45 μM), VT1598 (0.25 μM), and VT1161 (0.20 μM). The crystal structures of A. castellanii CYP51 with bound VT1161 (2.24 Å) and without an inhibitor (1.95 Å), presented here, can be used in the development of azole-based scaffolds to achieve optimal amoebicidal effectiveness.

Synthesis, In Silico Study, and In Vitro Antifungal Activity of New 5-(1,3-Diphenyl-1H-Pyrazol-4-yl)-4-Tosyl-4,5-Dihydrooxazoles

The increase in multi-drug resistant Candida strains has caused a sharp rise in life-threatening fungal infections in immunosuppressed patients, including those with SARS-CoV-2. Novel antifungal drugs are needed to combat multi-drug-resistant yeasts. This study aimed to synthesize a new series of 2-oxazolines and evaluate the ligands in vitro for the inhibition of six Candida species and in silico for affinity to the CYP51 enzymes (obtained with molecular modeling and protein homology) of the same species. The 5-(1,3-diphenyl-1H-pyrazol-4-yl)-4-tosyl-4,5-dihydrooxazoles 6a-j were synthesized using the Van Leusen reaction between 1,3-diphenyl-4-formylpyrazoles 4a-j and TosMIC 5 in the presence of K2CO3 or KOH without heating, resulting in short reaction times, high compound purity, and high yields. The docking studies revealed good affinity for the active site of the CYP51 enzymes of the Candida species in the following order: 6a-j > 4a-j > fluconazole (the reference drug). The in vitro testing of the compounds against the Candida species showed lower MIC values for 6a-j than 4a-j, and for 4a-j than fluconazole, thus correlating well with the in silico findings. According to growth rescue assays, 6a-j and 4a-j (like fluconazole) inhibit ergosterol synthesis. The in silico toxicity assessment evidenced the safety of compounds 6a-j, which merit further research as possible antifungal drugs.

Unleashing the potential of vanillic acid: A new twist on nature's recipe to fight inflammation and circumvent azole-resistant fungal infections

Vanillic acid (VA) - a naturally occurring phenolic compound in plants - is not only used as a flavoring agent but also a prominent metabolite post tea consumption. VA and its associated compounds are believed to play a significant role in preventing diseases, underscoring the need for a systematic investigation. Herein, we report a 4-step synthesis employing the classical organic reactions, such as Willamson's alkylation, Fischer-Spier reaction, and Steglich esterification, complemented with a protection-deprotection strategy to prepare 46 VA derivatives across the five series (1a-1i, 2a-2i, 3, 3a-3i, 4a-4i, 5a-5i) in high yields. The synthesized compounds were investigated for their antifungal, anti-inflammatory, and toxic effects. Notably, compound 1a demonstrated remarkable ROS inhibition with an IC50 value of 5.1 ± 0.7 µg/mL, which is more than twice as effective as the standard ibuprofen drug. A subset of the synthesized derivatives (2b, 2c, 2e, 3b-3d, 4a-4c, 5a, and 5e) manifested their antifungal effect against drug-resistant Candida strains. Compound 5g, in particular, revealed synergism with the established antifungal drugs amphotericin B (AMB) and fluconazole (FLZ), doubling FLZ's potency against azole resistant Candida albican ATCC 36082. Furthermore, 5g improved the potency of these antifungals against FLZ-sensitive strains, including C. glabrata ATCC 2001 and C. parapsilosis ATCC 22019, as well as various multidrug-resistant (MDR) Candida strains, namely C. albicans ATCC 14053, C. albicans CL1, and C. krusei SH2L OM341600. Additionally, pharmacodynamics of compound 5g was examined using time-kill assay, and a benign safety profile was observed with no hemolytic activity in whole blood, and no cytotoxicity towards the normal BJ human cell line. The synergistic potential of 5g was further investigated through both experimental methods and docking simulations.These findings highlight the therapeutic potential of VA derivatives, particularly in addressing inflammation and circumventing FLZ resistance in Candida albicans.

Indole clubbed 2,4-thiazolidinedione linked 1,2,3-triazole as a potent antimalarial and antibacterial agent against drug-resistant strain and molecular modeling studies

In the face of escalating challenges of microbial resistance strains, this study describes the design and synthesis of 5-({1-[(1H-1,2,3-triazol-4-yl)methyl]-1H-indol-3-yl}methylene)thiazolidine-2,4-dione derivatives, which have demonstrated significant antimicrobial properties. Compared with the minimum inhibitory concentrations (MIC) values of ciprofloxacin on the respective strains, compounds 5a, 5d, 5g, 5l, and 5m exhibited potent antibacterial activity with MIC values ranging from 16 to 25 µM. Almost all the synthesized compounds showed lower MIC compared to standards against vancomycin-resistant enterococcus and methicillin-resistant Staphylococcus aureus strains. Additionally, the majority of the synthesized compounds demonstrated remarkable antifungal activity, against Candida albicans and Aspergillus niger, as compared to nystatin, griseofulvin, and fluconazole. Furthermore, the majority of compounds exhibited notable inhibitory effects against the Plasmodium falciparum strain, having IC50 values ranging from 1.31 to 2.79 μM as compared to standard quinine (2.71 μM). Cytotoxicity evaluation of compounds 5a-q on SHSY-5Y cells at up to 100 μg/mL showed no adverse effects. Comparison with control groups highlights their noncytotoxic characteristics. Molecular docking confirmed compound binding to target active sites, with stable protein-ligand complexes displaying drug-like molecules. Molecular dynamics simulations revealed dynamic stability and interactions. Rigorous tests and molecular modeling unveil the effectiveness of the compounds against drug-resistant microbes, providing hope for new antimicrobial compounds with potential safety.

Natural Isatin Derivatives Against Black Fungus: In Silico Studies

During this coronavirus pandemic, when a lot of people are already severely afflicted with SARS-CoV-19, the dispersion of black fungus is making it worse, especially in the Indian subcontinent. Considering this situation, the idea for an in silico study to identify the potential inhibitor against black fungal infection is envisioned and computational analysis has been conducted with isatin derivatives that exhibit considerable antifungal activity. Through this in silico study, several pharmacokinetics properties like absorption, distribution, metabolism, excretion, and toxicity (ADMET) are estimated for various derivatives. Lipinski rules have been used to observe the drug likeliness property, and to study the electronic properties of the molecules, quantum mechanism was analyzed using the density functional theory (DFT). After applying molecular docking of the isatin derivatives with sterol 14-alpha demethylase enzyme of black fungus, a far higher docking affinity score has been observed for the isatin sulfonamide-34 (derivative 1) than the standard fluconazole. Lastly, molecular dynamic (MD) simulation has been performed for 100 ns to examine the stability of the proposed drug complex by estimating Root Mean Square Deviation (RMSD), Radius of gyration (Rg), Solvent accessible surface area (SASA), Root Mean Square Fluctuation (RMSF), as well as hydrogen bond. Listed ligands have precisely satisfied every pharmacokinetics requirement for a qualified drug candidate and they are non-toxic, non-carcinogenic, and have high stability. This natural molecule known as isatin derivative 1 has shown the potential of being a drug for fungal treatment. However, the impact of the chemicals on living cells requires more investigation and research.

Innovations in Antifungal Drug Discovery among Cell Envelope Synthesis Enzymes through Structural Insights

Life-threatening systemic fungal infections occur in immunocompromised patients at an alarming rate. Current antifungal therapies face challenges like drug resistance and patient toxicity, emphasizing the need for new treatments. Membrane-bound enzymes account for a large proportion of current and potential antifungal targets, especially ones that contribute to cell wall and cell membrane biosynthesis. Moreover, structural biology has led to a better understanding of the mechanisms by which these enzymes synthesize their products, as well as the mechanism of action for some antifungals. This review summarizes the structures of several current and potential membrane-bound antifungal targets involved in cell wall and cell membrane biosynthesis and their interactions with known inhibitors or drugs. The proposed mechanisms of action for some molecules, gleaned from detailed inhibitor-protein studeis, are also described, which aids in further rational drug design. Furthermore, some potential membrane-bound antifungal targets with known inhibitors that lack solved structures are discussed, as these might be good enzymes for future structure interrogation.

Design, synthesis and evaluation of 2-phenylpyrimidine derivatives as novel antifungal agents targeting CYP51

Invasive fungal infections, with high morbidity and mortality, have become one of the most serious threats to human health. There are a few kinds of clinical antifungal drugs but large amounts of them are used, so there is an urgent need for a new structural type of antifungal drug. In this study, we carried out three rounds of structural optimisation and modification of the compound YW-01, which was obtained from the preliminary screening of the group, by using the strategy of scaffold hopping. A series of novel phenylpyrimidine CYP51 inhibitors were designed and synthesised. In vitro antifungal testing showed that target compound C6 exhibited good efficacy against seven common clinically susceptible strains, which was significantly superior to the clinical first-line drug fluconazole. Subsequently in vitro tests on metabolic stability and cytotoxicity revealed that C6 was safe and stable for hepatic microsomal function. Finally, C6 warranted further exploration as a possible novel structural type of CYP51 inhibitor.

Evaluation of the antidermatophytic activity of potassium salts of N-acylhydrazinecarbodithioates and their aminotriazole-thione derivatives

Nowadays, dermatophyte infections are relatively easy to cure, especially since the introduction of orally administered antifungals such as terbinafine and itraconazole. However, these drugs may cause side effects due to liver damage or their interactions with other therapeutics. Hence, the search for new effective chemotherapeutics showing antidermatophyte activity seems to be the urge of the moment. Potassium salts of N-acylhydrazinecarbodithioates are used commonly as precursors for the synthesis of biologically active compounds. Keeping that in mind, the activity of a series of five potassium N-acylhydrazinecarbodithioates (1a-e) and their aminotriazole-thione derivatives (2a-e) was evaluated against a set of pathogenic, keratinolytic fungi, such as Trichophyton ssp., Microsporum ssp. and Chrysosporium keratinophilum, but also against some Gram-positive and Gram-negative bacteria. All tested compounds were found non-toxic for L-929 and HeLa cells, with the IC30 and IC50 values assessed in the MTT assay above 128 mg/L. The compound 5-amino-3-(naphtalene-1-yl)-4,5-dihydro-1H-1,2,4-triazole-5-thione (2d) was found active against all fungal strains tested. Scanning Electron Microscopy (SEM) revealed inhibition of mycelium development of Trichophyton rubrum cultivated on nail fragments and treated with 2d 24 h after infection with fungal spores. Transmission Electron Microscopy (TEM) observation of mycelium treated with 2d showed ultrastructural changes in the morphology of germinated spores. Finally, the RNA-seq analysis indicated that a broad spectrum of genes responded to stress induced by the 2d compound. In conclusion, the results confirm the potential of N-acylhydrazinecarbodithioate derivatives for future use as promising leads for new antidermatophyte agents development.

The development of thymol-isatin hybrids as broad-spectrum antibacterial agents with potent anti-MRSA activity

Bacterial resistance toward available therapeutic agents has become a nightmare for the healthcare system, causing significant mortality as well as prolonged hospitalization, thereby needing the urgent attention of research groups working on antimicrobial drug development worldwide. Molecular hybridization is a well-established tool for developing multifunctional compounds to tackle drug resistance. Inspired by the antibacterial profiles of isatin and thymol, along with the efficiency of a triazole linker in molecular hybridization, herein, we report the design, synthesis and antibacterial activity of a novel series of triazole tethered thymol-isatin hybrids. Most of the hybrids exhibited a broad-spectrum antibacterial efficacy against standard human pathogenic as well as clinically isolated multidrug-resistant bacterial strains listed in the WHO's 'priority pathogen' list and also in the ESKAPE group. Among them, hybrid compound AS8 was the most effective against methicillin-resistant Staphylococcus aureus (MIC = 1.9 μM and MBC = 3.9 μM), exhibiting biofilm inhibitory potential. AS8 exhibited dehydrosqualene synthase (CrtM) inhibitory potential in MRSA and decreased the production of virulence factor staphyloxanthin, which is one of the key mechanisms of its anti-MRSA efficacy, which was further supported by molecular docking and simulation studies. Moreover, AS8 was found to be non-toxic and showed a potent in vivo antibacterial efficacy (90% survival at 10 mg kg-1) as well as a modulated immune response in the larva-based (Galleria mellonella) model of systemic infections. Overall findings confirmed that AS8 can be a promising candidate or take the lead in the treatment and further drug development against drug-resistant infectious diseases, especially against MRSA infections.

Design, synthesis, evaluation and optimization of novel azole analogues as potent antifungal agents

In order to develop antifungal drugs, a series of novel azole analogues were designed and synthesized based on our previous work. Most of the target compounds had broad-spectrum antifungal activity, which showed excellent to moderate inhibitory activity against the tested strains, except A. fum 0504656. Among these, compounds B3, B7, B8, B11, B12 and E9 showed excellent activity against C. alb Y0109 and C. alb SC5314 (with the MIC80: 0.0156 ug/mL). In addition, compound B3 showed the best inhibitory activity against fluconazole-resistant strains C. alb 901 and C. alb 904, and had low toxicity against NIH/3T3 cells at the effective MIC range against fungi. Structure-activity relationship and docking studies of the derivatives suggest that the presence of the 2-fluoro-4-hydroxyphenyl and 1,2,3-triazole group enhance the antifungal activity of the compounds, which may be related to the interaction of the key groups with the amino acids surrounding the target enzyme.