Fungal Lanosterol 14α-demethylase: A target for next-generation antifungal design

Recent in vitro advances in the ocular antimicrobial agents against Acanthamoeba

This review examines the advancements in antimicrobial drug discovery with in vitro assays for Acanthamoeba, highlighting the efficacy of current topical antimicrobial agents. In recent decades, the treatment and diagnosis of Acanthamoeba keratitis (AK) have presented clinical challenges. Clinicians often rely on clinical judgment, risk factors, and patient travel history to guide initial treatment decisions. The clinical presentation of AK frequently coincides with bacterial and fungal keratitis, leading to delays in diagnostic confirmation. This review compiles a list of commonly used antimicrobial agents that may be useful in controlling and preventing Acanthamoeba and other microbial infections during the diagnostic waiting period. Due to their unique life cycle, consisting of both trophozoite and cyst stages, amoebae exhibit resistance to various clinical drugs. Current research efforts are focused on identifying alternative and effective treatment options. Despite the ongoing characterization of various cytocidal agents from natural and synthetic sources, chlorhexidine gluconate (CHG) and polyhexamethylene biguanide (PHMB) have emerged as the most effective therapies for AK. Drawing from previous studies, we catalog several commonly used antimicrobial agents that may enhance the efficacy of PHMB and CHG while also preventing other microbial infections. These alternative agents present promising options for treating AK cases. This review evaluates progress in anti-amoebic drug discovery, focusing on antibiotics and cataloging their activity at different stages of Acanthamoeba.

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.

Exploring USFDA-Approved Imidazole-Based Small Molecules in Drug Discovery: A Mini Perspective

In the present work, we have explored the importance of the imidazole ring and its importance in drug discovery, citing the key approvals in the present decade (2013-2024). The pharmacological attribution for the approved drugs revealed that out of 20 approved drugs, 45% of the approvals were made as anti-infectives, followed by approvals under the category of genetic and metabolic disorders, sexual endocrine disorders, anticancer, and to treat blood pressure, gastrointestinal disorders, and neurological conditions. Most approved drugs were dispensed through solid dosage forms (13) and thus had predominantly oral routes beside others. The metabolism pattern revealed that the drugs undergo metabolism via the involvement of multiple enzymes, where CYP3A4 and CYP3A5 were the core enzymes. The excretion pattern of these drugs revealed that the drugs are majorly excreted via the fecal route. The chemical analysis showed that pyrrolidine/pyrrole was the major heterocycle in the approved drugs, followed by the indole ring in the hybridization. Considering the substitution pattern, most drugs possessed amide, amines, and fluoro group as the functional substitution with the 2,4-substitution pattern seen in most approved drugs. Besides this, the three approved drugs were found to possess chiral centers and exhibit chirality. The article also expanded to cover the synthetic routes and metabolic routes for this versatile ring system and case studies for its utility to serve as bioisostere in drug discovery. Furthermore, this article also presents the receptor-ligand interactions of imidazole-based drugs with various target receptors. The present article is, therefore, put forth to assist medicinal chemists and chemists working in drug discovery of this versatile ring system.

Behavioral and physiological effects of difenoconazole on stingless bees: A multi-species analysis

Stingless bees, vital to ecosystems and plant production, face increasing threats from pesticide use, with poorly understood potential impacts of fungicides on these pollinators. The goal of this work was to evaluate the effect of contact or oral exposure to difenoconazole, a broad-spectrum fungicide, on foragers of three species of stingless bees: Frieseomelitta varia, Melipona mondury, and Trigona spinipes. The study employed a field-realistic dose of difenoconazole (0.075 mg a.i./mL, referred to as 1×) and its dilutions (10× or 100×) to assess survival and food consumption. The recommended field dose was used to evaluate behaviors, as well as total hemocyte count (THC), and midgut morphology. Contact or oral exposure increased THC in F. varia, while oral exposure decreased food consumed, distance walked, and social interactions, and caused injuries to the midgut. In M. mondury, contact exposure decreased survival and THC while increasing interactions, whereas oral exposure increased walking distance and interactions. For T. spinipes, contact exposure increased walking distance and interactions. Exposures caused adverse effects with variations in the level or type of damage depending on the species and route of exposure. This emphasizes the significance of understanding the potential impacts of fungicides on various pollinators, particularly on stingless bees.

Determination of the zebrafish embryo developmental toxicity assessment (ZEDTA) as an alternative non-mammalian approach for the safety assessment of agrochemicals

With the US Environment Protection Agency reducing requests for (and funding of) mammalian studies alongside the proposed elimination of requests by 2035, there is an urgent need for fully validated New Approach Methods (NAMs) to fill the resultant gap for safety assessment of agrochemicals. One promising NAM for assessing the potential for human prenatal developmental toxicity potential is the Zebrafish Embryo Developmental Toxicity Assessment, a bioassay that has been used by the pharmaceutical industry for more than a decade in early-stage drug safety assessment. Despite its promise, little data has been generated to assess the validity of ZEDTA for assessing Developmental and Reproductive Toxicity of new agrochemical products. Addressing this knowledge gap, we tested 67 compounds (insecticides, herbicides and fungicides) spanning multiple different chemical groupings and mechanisms of action. ZEDTA assay results were compared with the European Chemicals Agency (ECHA) Classification and Labelling (C&L) for mammalian hazard classification and with publicly available data to determine the ZEDTA's translation power. Overall, the ZEDTA assay had an effective detection capability of 65 % for sensitivity and 64 % for specificity as compared with the ECHA-C&L classification and publicly available data. Comparing the ZEDTA data there were both strengths and weaknesses in alignments for across the different chemical classes and chemical mechanisms of action. Overall, the data generated, show the performance of the ZEDTA assay was comparable with other bioassays highlighted as alternatives for mammalian assessment and holds good promise as a NAM for screening agrochemical prenatal developmental toxicity during new product human safety assessment.

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.

Mechanisms of Azole Potentiation: Insights from Drug Repurposing Approaches

The emergence of azole resistance and tolerance in pathogenic fungi has emerged as a significant public health concern, emphasizing the urgency for innovative strategies to bolster the efficacy of azole-based treatments. Drug repurposing stands as a promising and practical avenue for advancing antifungal therapy, with the potential for swift clinical translation. This review offers a comprehensive overview of azole synergistic agents uncovered through drug repurposing strategies, alongside an in-depth exploration of the mechanisms by which these agents augment azole potency. Drawing from these mechanisms, we delineate strategies aimed at enhancing azole effectiveness, such as inhibiting efflux pumps to elevate azole concentrations within fungal cells, intensifying ergosterol synthesis inhibition, mitigating fungal cell resistance to azoles, and disrupting biological processes extending beyond ergosterol synthesis. This review is beneficial for the development of these potentiators, as it meticulously examines instances and provides nuanced discussions on the mechanisms underlying the progression of azole potentiators through drug repurposing strategies.

The O-glycosyltransferase C1GALT1 promotes EWSR1::FLI1 expression and is a therapeutic target for Ewing sarcoma

Ewing sarcoma (ES) is an aggressive bone cancer driven by the oncogenic fusion-protein EWSR1::FLI1, which is not present in normal cells and is therefore an attractive therapeutic target. However, as a transcription factor, EWSR1::FLI1 is considered undruggable. Factors that promote EWSR1::FLI1 expression, and thus whose inhibition would reduce EWSR1::FLI1 protein levels and function, are potential drug targets. Here, using genome-scale CRISPR/Cas9 knockout screening, we identify C1GALT1, a galactosyltransferase required for the biosynthesis of many O-glycoproteins, as a factor that promotes EWSR1::FLI1 expression. We show that C1GALT1 acts by O-glycosylating the pivotal Hedgehog (Hh) signaling component Smoothened (SMO), thereby stabilizing SMO and stimulating the Hh pathway, which we find directly activates EWSR1::FLI1 transcription. Itraconazole, an FDA-approved anti-fungal agent that is known to inhibit C1GALT1, reduces EWSR1::FLI1 levels in ES cell lines and suppresses growth of ES xenografts in mice. Our study reveals a therapeutically targetable mechanism that promotes EWSR1::FLI1 expression and ES tumor growth.

Effective adaptation of flight muscles to tebuconazole-induced oxidative stress in honey bees

The widespread and excessive agricultural use of azole fungicide tebuconazole poses a major threat to pollinator species including honey bee colonies as highlighted by recent studies. This issue is of growing importance, due to the intensification of modern agriculture and the increasing amount of the applied chemicals, serving as a major and recent problem from both an ecotoxicological and an agricultural point of view. The present study aims to detect the effects of acute sublethal tebuconazole exposure focusing on the redox homeostasis of honey bee flight muscles. The results show that the redox homeostasis, especially the glutathione system, of the exposed animals is severely impaired by the treatment, but flight muscles are able to successfully counteract the detrimental effects by the effective activation of protective processes. This efficient adaptation may have led to overcompensation processes eventually resulting in lower hydrogen peroxide and malondialdehyde concentrations after exposure. It could also be assumed that tebuconazole has a non-monotonic dose-response curve similarly to many other substances with endocrine-disrupting activity concerning parameters such as superoxide dismutase activity or total antioxidant capacity. These findings shed light on the detrimental impact of tebuconazole on the redox balance of honey bee flight muscles, also highlighting, that unlike other organs such as the brain, they may effectively adapt to acute tebuconazole exposure.

Gaining molecular insights towards inhibition of foodborne fungi Aspergillus fumigatus by a food colourant violacein via computational approach

Filamentous Fungal Human Pathogens (FFHPs) such as Aspergillus fumigatus, are growing resistant to currently available antifungal drugs. One possible target, the Nucleoside diphosphate kinase (Ndk) is significant for nucleotide biosynthesis and crucial for fungal metabolism. Violacein, a natural food colorant, was examined for its antifungal effects against Aspergillus fumigatus via computational approach against the Ndk protein. Known and predicted interactions of Ndk with proteins was performed using the STRING application. Molecular docking was performed using Schrodinger Maestro software (V.14.1) under enhanced precision docking, with OPLS4 forcefield. MDS was performed for 500ns under OPLS4 forcefield and the TIP3P solvent system. The geometry optimization for DFT was performed using the Becke 3-parameter exchange functional (B3LYP) method. The Molecular Docking Studies revealed significant interactions with good binding energy between Violacein and Ndk. Subsequent MD Simulations confirmed the stability of Violacein-Ndk complex, compared to the reference ligand-complex, indicating a stable interaction between the protein and violacein. The energy band gap of violacein was found to be 0.072567 eV suggesting its softness with lower kinetic stability and higher chemical reactivity. The results suggest Violacein could potentially disrupt nucleotide metabolism by targeting Ndk, thus demonstrating antifungal activity. However, further experimental validation is required to confirm these computational findings and explore the practical use of Violacein in antifungal treatments.

The Molecular Basis of the Intrinsic and Acquired Resistance to Azole Antifungals in Aspergillus fumigatus

Aspergillus fumigatus is intrinsically resistant to the widely used antifungal fluconazole, and therapeutic failure can result from acquired resistance to voriconazole, the primary treatment for invasive aspergillosis. The molecular basis of substrate specificity and innate and acquired resistance of A. fumigatus to azole drugs were addressed using crystal structures, molecular models, and expression in Saccharomyces cerevisiae of the sterol 14α-demethylase isoforms AfCYP51A and AfCYP51B targeted by azole drugs, together with their cognate reductase AfCPRA2 and AfERG6 (sterol 24-C-methyltransferase). As predicted by molecular modelling, functional expression of CYP51A and B required eburicol and not lanosterol. A crowded conformationally sensitive region involving the BC-loop, helix I, and the heme makes AfCYP51A T289 primarily responsible for resistance to fluconazole, VT-1161, and the agrochemical difenoconazole. The Y121F T289A combination was required for higher level acquired resistance to fluconazole, VT-1161, difenoconazole, and voriconazole, and confirms posaconazole, isavuconazole and possibly ravuconazole as preferred treatments for target-based azole-resistant aspergillosis due to such a combination of mutations.

Green Fabrication of Silver Nanoparticles, Statistical Process Optimization, Characterization, and Molecular Docking Analysis of Their Antimicrobial Activities onto Cotton Fabrics

Nanotechnological methods for creating multifunctional fabrics are attracting global interest. The incorporation of nanoparticles in the field of textiles enables the creation of multifunctional textiles exhibiting UV irradiation protection, antimicrobial properties, self-cleaning properties and photocatalytic. Nanomaterials-loaded textiles have many innovative applications in pharmaceuticals, sports, military the textile industry etc. This study details the biosynthesis and characterization of silver nanoparticles (AgNPs) using the aqueous mycelial-free filtrate of Aspergillus flavus. The formation of AgNPs was indicated by a brown color in the extracellular filtrate and confirmed by UV-Vis spectroscopy with a peak at 426 nm. The Box-Behnken design (BBD) is used to optimize the physicochemical parameters affecting AgNPs biosynthesis. The desirability function was employed to theoretically predict the optimal conditions for the biosynthesis of AgNPs, which were subsequently experimentally validated. Through the desirability function, the optimal conditions for the maximum predicted value for the biosynthesized AgNPs (235.72 µg/mL) have been identified as follows: incubation time (58.12 h), initial pH (7.99), AgNO3 concentration (4.84 mM/mL), and temperature (34.84 °C). Under these conditions, the highest experimental value of AgNPs biosynthesis was 247.53 µg/mL. Model validation confirmed the great accuracy of the model predictions. Scanning electron microscopy (SEM) revealed spherical AgNPs measuring 8.93-19.11 nm, which was confirmed by transmission electron microscopy (TEM). Zeta potential analysis indicated a positive surface charge (+1.69 mV), implying good stability. X-ray diffraction (XRD) confirmed the crystalline nature, while energy-dispersive X-ray spectroscopy (EDX) verified elemental silver (49.61%). FTIR findings indicate the presence of phenols, proteins, alkanes, alkenes, aliphatic and aromatic amines, and alkyl groups which play significant roles in the reduction, capping, and stabilization of AgNPs. Cotton fabrics embedded with AgNPs biosynthesized using the aqueous mycelial-free filtrate of Aspergillus flavus showed strong antimicrobial activity. The disc diffusion method revealed inhibition zones of 15, 12, and 17 mm against E. coli (Gram-negative), S. aureus (Gram-positive), and C. albicans (yeast), respectively. These fabrics have potential applications in protective clothing, packaging, and medical care. In silico modeling suggested that the predicted compound derived from AgNPs on cotton fabric could inhibit Penicillin-binding proteins (PBPs) and Lanosterol 14-alpha-demethylase (L-14α-DM), with binding energies of -4.7 and -5.2 Kcal/mol, respectively. Pharmacokinetic analysis and sensitizer prediction indicated that this compound merits further investigation.

Antifungal Efficacy of Ultrashort β-Peptides against Candida Species: Mechanistic Understanding and Therapeutic Implications

Candidiasis, a condition spurred by the unchecked proliferation of Candida species, poses a formidable global health threat, particularly in immunocompromised individuals. The emergence of drug-resistant strains complicates management strategies, necessitating novel therapeutic avenues. Antimicrobial peptides (AMPs) have garnered attention for their potent antifungal properties and broad-spectrum activity against Candida species. This study assessed the antifungal effectiveness of ultrashort β-peptides against Candida strains, with a specific focus on peptide P3 (LAU-β3,3-Pip-β2,2-Ac6c-PEA). Our findings showed P3's remarkable fungistatic and fungicidal activities against Candida albicans, exhibiting an MIC of 4 μg/mL, comparable to those of standard antifungal drugs. The MIC value remained unchanged in the presence of ADC and BSA, indicating that serum albumin does not diminish the activity of P3. P3 demonstrates synergistic effects when combined with Fluconazole (FLU), Itraconazole (ITR), and Nystatin (NYS) to the extent that it becomes effective at 0.125, 0.125, and 0.03125 μg/mL, respectively. Concentration versus time-kill kinetics showed its time-dependent activity up to the first 12 h against C. albicans, and later concentration also played a role; indeed, at 24 h the whole culture was sterilized at 8× MIC. Post-antifungal effect assays confirmed prolonged suppression of pathogen growth after the removal of P3 from the media for significant durations. More importantly, P3 inhibits hyphae formation and biofilm development of Candida, outperforming Fluconazole with respect to these properties. Mechanistic insights display P3's potential to disrupt fungal cell membrane integrity and dose-dependent inhibition of ergosterol biosynthesis, essential for fungal cell wall integrity. Using the Bradford assay, it was observed that extracellular protein concentrations increased with higher doses of the compound, thereby validating the effect of P3 on membrane integrity. A comparative gene analysis using RT-PCR showed that P3 downregulates ERG3, ERG11, and HWP1, which are crucial for the survival and pathogenicity of C. albicans. The impact of P3 on ERG11 and ERG3 is more effective than that of Fluconazole. Molecular docking studies revealed strong binding of P3 to various isoforms of lanosterol 14-α-demethylase, a key enzyme in ergosterol synthesis. Furthermore, molecular dynamic simulations validated the stability of the most promising docking complex. Overall, our findings underscore P3's potential as a leading candidate for the development of innovative antifungal therapies, warranting further investigation and optimization.

Potent Antimicrobial Azoles: Synthesis, In Vitro and In Silico Study

Background/Objectives: The increase in fungal infections, both systemic and invasive, is a major source of morbidity and mortality, particularly among immunocompromised people such as cancer patients and organ transplant recipients. Because of their strong therapeutic activity and excellent safety profiles, azole antifungals are currently the most extensively used systemic antifungal drugs. Antibacterial properties of various topical antifungals, such as oxiconazole, which features oxime ether functionality, were discovered, indicating an exciting prospect in antimicrobial chemotherapy. Methods: In this study, eleven new oxime ether derivatives with the azole scaffold (5a-k) were synthesized and tested for their antimicrobial effects using the microdilution method to obtain broad-spectrum hits. Results: Although the title compounds showed limited efficacy against Candida species, they proved highly effective against dermatophytes. Compounds 5c and 5h were the most potent derivatives against Trichophyton mentagrophytes and Arthroderma quadrifidum, with minimum inhibitory concentration (MIC) values lower than those of the reference drug, griseofulvin. The MIC of 5c and 5h were 0.491 μg/mL and 0.619 μg/mL against T. mentagrophytes (MIC of griseofulvin: 2.52 μg/mL). The compounds were also tested against Gram-positive and Gram-negative bacteria. Briefly, 5c was the most active against Escherichia coli and Bacillus subtilis, with MIC values much better than that of ciprofloxacin (MIC of 5c = 1.56 μg/mL and 1.23 μg/mL, MIC of ciprofloxacin = 31.49 and 125.99 μg/mL, respectively). Molecular docking suggested a good fit in the active site of fungal lanosterol 14α-demethylase (CYP51) and bacterial FtsZ (Filamenting temperature-sensitive mutant Z) protein. Conclusions: As a result, the title compounds emerged as promising entities with broad antifungal and antibacterial effects, highlighting the utility of oxime ether function in the azole scaffold.

Azole Combinations and Multi-Targeting Drugs That Synergistically Inhibit Candidozyma auris

Limited antifungal treatment options and drug resistance require innovative approaches to effectively combat fungal infections. Combination therapy is a promising strategy that addresses these pressing issues by concurrently targeting multiple cellular sites. The drug targets usually selected for combination therapy are from different cellular pathways with the goals of increasing treatment options and reducing development of resistance. However, some circumstances can prevent the implementation of combination therapy in clinical practice. These could include the increased risk of adverse effects, drug interactions, and even the promotion of drug resistance. Furthermore, robust clinical evidence supporting the superiority of combination therapy over monotherapy is limited and underscores the need for further research. Despite these challenges, synergies detected with different antifungal classes, such as the azoles and echinocandins, suggest that treatment strategies can be optimized by better understanding the underlying mechanisms. This review provides an overview of multi-targeting combination strategies with a primary focus on Candidozyma auris infections.

Thermophilic fungus uses anthraquinones to modulate ferrous excretion, sterol-mediated endocytosis, and iron storage in response to cold stress

To date, there are no real physiological mechanisms for iron excretion in eukaryote, and no physiological "actuator" that can control all the three fundamental biologic processes of absorption, storage, and excretion. Here, we observed that the accumulation of anthraquinones by Thermomyces dupontii under cold stress can achieve this process. Through mutation analysis, we found that mutant ΔAn deficiency in anthraquinones accumulated ferrous and total free iron due to adopting a rare lifestyle with no endocytosis but accumulation of membrane-derived vesicles. Anthraquinone complement indicated that the vesicles in ΔAn could coat the extrinsic anthraquinone-induced granules to prevent contact with the fungal interiors. Detailed chemical investigation on ΔAn led to characterization of a rare oxygen-free ergosterene with unstable nature in air as the major membrane steroid in ΔAn, suggesting hypoxia inner in ΔAn cells, consistent with dramatically low oxygen-consuming rates in ΔAn. A series of physiological and metabolic analyses indicated anthraquinones were involved in exporting ferrous and promoting formation of oxygen-containing metabolites, including ergosterols for endocytosis and iron chelators for iron storage. Moreover, we found that both the anticancer agent mitoxantrone with well-known-cardiotoxicity side effect and the major terpenoid-derived polycyclic aromatics from Danshen for treating cardiovascular disease showed potent ferrous transporting capabilities in human cancer cells. Our findings provide a novel insight into the underlying mechanisms of polycyclic aromatics in nature and pharmacology, and offer a new strategy for developing potential therapeutics and agents for membrane transport, iron homestasis, and anticold.

Drug to genome to drug: a computational large-scale chemogenomics screening for novel drug candidates against sporotrichosis

Sporotrichosis is recognized as the predominant subcutaneous mycosis in South America, attributed to pathogenic species within the Sporothrix genus. Notably, in Brazil, Sporothrix brasiliensis emerges as the principal species, exhibiting significant sapronotic, zoonotic and enzootic epidemic potential. Consequently, the discovery of novel therapeutic agents for the treatment of sporotrichosis is imperative. The present study is dedicated to the repositioning of pharmaceuticals for sporotrichosis therapy. To achieve this goal, we designed a pipeline with the following steps: (a) compilation and preparation of Sporothrix genome data; (b) identification of orthologous proteins among the species; (c) identification of homologous proteins in publicly available drug-target databases; (d) selection of Sporothrix essential targets using validated genes from Saccharomyces cerevisiae; (e) molecular modeling studies; and (f) experimental validation of selected candidates. Based on this approach, we were able to prioritize eight drugs for in vitro experimental validation. Among the evaluated compounds, everolimus and bifonazole demonstrated minimum inhibitory concentration (MIC) values of 0.5 µg/mL and 4.0 µg/mL, respectively. Subsequently, molecular docking studies suggest that bifonazole and everolimus may target specific proteins within S. brasiliensis- namely, sterol 14-α-demethylase and serine/threonine-protein kinase TOR, respectively. These findings shed light on the potential binding affinities and binding modes of bifonazole and everolimus with their probable targets, providing a preliminary understanding of the antifungal mechanism of action of these compounds. In conclusion, our research advances the understanding of the therapeutic potential of bifonazole and everolimus, supporting their further investigation as antifungal agents for sporotrichosis in prospective hit-to-lead and preclinical investigations.

Design, synthesis, docking studies and bioactivity evaluation of 1,2,3-triazole eugenol derivatives

Aim: The design, synthesis, docking studies and evaluation of the in vitro antifungal and cytotoxic properties of eugenol (EUG) containing 1,2,3-triazole derivatives are reported. Most of the derivatives have not been reported.Materials & methods: The EUG derivatives were synthesized, molecular docked and tested for their antifungal activity.Results: The compounds showed potent antifungal activity against Trichophyton rubrum, associated with dermatophytosis. Compounds 2a and 2i exhibited promising results, with 2a being four-times more potent than EUG. The binding mode prediction was similar to itraconazole in the lanosterol-14-α-demethylase wild-type and G73E mutant binding sites. Additionally, the pharmacokinetic profile prediction suggests good gastrointestinal absorption and potential oral administration.Conclusion: Compound 2a is a promising antifungal agent against dermatophytosis caused by T. rubrum.

MBX-7591: a promising drug candidate against drug-resistant fungal infections

Invasive fungal infections (IFIs) caused by pathogenic fungi pose a significant public health concern, particularly for immunocompromised individuals. Mortality rates for IFIs remain high, and currently available treatment options are limited. Existing antifungal agents often suffer from limited clinical efficacy, poor fungicidal activity within the host, potential toxicity, and increasing ineffectiveness due to emerging resistance, especially against triazole drugs, the current mainstay of antifungal treatment. A recent study has identified MBX-7591, a small molecule with promising antifungal activity against Aspergillus fumigatus and other pathogenic fungi, including strains resistant to triazoles (C. Gutierrez-Perez, C. Puerner, J. T. Jones, S. Vellanki, E. M. Vesely, et al., mBio e01166-24, 2024, https://doi.org/10.1128/mbio.01166-24). This novel compound appears to inhibit stearoyl-CoA 9-desaturase, a key enzyme involved in fungal fatty acid biosynthesis. By disrupting the conversion of saturated fatty acids to oleic acid, MBX-7591 offers a unique mechanism of action, potentially reducing the risk of resistance development. Here, we now discuss the implications of these groundbreaking findings for overcoming antifungal drug resistance.

Intermolecular Aza-Wacker Coupling of Alkenes with Azoles by Photo-Aerobic Selenium-π-Acid Multicatalysis

Herein, the intermolecular, photoaerobic aza-Wacker coupling of azoles with alkenes by means of dual and ternary selenium-π-acid multicatalysis is presented. The title method permits an expedited avenue toward a broad scope of N-allylated azoles and representative azinones under mild conditions with broad functional group tolerance, as is showcased in more than 60 examples including late-stage drug derivatizations. From a regiochemical perspective, the protocol is complementary to cognate photoredox catalytic olefin aminations, as they typically proceed through either allylic hydrogen atom abstraction or single electron oxidation of the alkene substrate. These methods predominantly result in C-N bond formations at the allylic periphery of the alkene or the less substituted position of the former π-bond (i.e., anti-Markovnikov selectivity). The current process, however, operates through a radical-polar crossover mechanism, which solely affects the selenium catalyst, thus allowing the alkene to be converted strictly through an ionic two-electron transfer regime under Markovnikov control. In addition, it is shown that the corresponding N-vinyl azoles can also be accessed by sequential or one-pot treatment of the allylic azoles with base, thus emphasizing the exquisite utility of this method.

Design, Synthesis, and 3D-QASR of 2-Ar-1,2,3-triazole Derivatives Containing Hydrazide as Potential Fungicides

A series of novel 2-Ar-1,2,3-triazole derivatives were designed and synthesized based on our previously discovered active compound 6d against Rhizoctonia solani. Most of these compounds exhibited good antifungal activity against R. solani at a concentration of 25 μg/mL. Based on the results of biological activity, we established a three-dimensional quantitative structure-activity relationship (3D-QSAR) model that guided the synthesis of compound 7y. Compound 7y exhibited superior activity against R. solani (EC50 = 0.47 μg/mL) compared to the positive controls hymexazol (EC50 = 12.80 μg/mL) and tebuconazole (EC50 = 0.87 μg/mL). Furthermore, compound 7y demonstrated better protective activity than the aforementioned two commercial fungicides in both detached leaf assays and greenhouse experiments, achieving 56.21% and 65.75% protective efficacy, respectively, at a concentration of 100 μg/mL. The ergosterol content was determined and molecular docking was performed to explore the mechanism of these active molecules. DFT calculation and MEP analysis were performed to illustrate the results of this study. These results suggest that compound 7y could serve as a novel 2-Ar-1,2,3-triazole lead compound for controlling R. solani.

New thymol-derived triazole exhibits promising activity against Trichophyton rubrum

Fungal infections have emerged worldwide, and azole antifungals are widely used to control these infections. However, the emergence of antifungal resistance has been compromising the effectiveness of these drugs. Therefore, the objective of this study was to evaluate the antifungal and cytotoxic activities of the nine new 1,2,3 triazole compounds derived from thymol that were synthesized through Click chemistry. The binding mode prediction was carried out by docking studies using the crystallographic structure of Lanosterol 14α-demethylase G73E mutant from Saccharomyces cerevisiae. The new compounds showed potent antifungal activity against Trichophyton rubrum but did not show relevant action against Aspergillus fumigatus and Candida albicans. For T. rubrum, molecules nº 5 and 8 showed promising results, emphasizing nº 8, whose fungicidal and fungistatic effects were similar to fluconazole. In addition, molecule nº 8 showed low toxicity for keratinocytes and fibroblasts, concluding that this compound demonstrates promising characteristics for developing a new drug for dermatophytosis caused by T. rubrum, or serves as a structural basis for further research.

Antifungal Potential of Secondary Metabolites Derived from Arcangelisia flava (L.) Merr.: An Analysis of In Silico Enzymatic Inhibition and In Vitro Efficacy against Candida Species

Considering the escalating resistance to conventional antifungal medications, it is critical to identify novel compounds that can efficiently counteract this challenge. The purpose of this research was to elucidate the fungicidal properties of secondary metabolites derived from Arcangelisia flava, with a specific focus on their efficacy against Candida species. This study utilized a combination approach comprising laboratory simulations and experiments to discern and evaluate the biologically active constituents present in the dichloromethane extract of A. flava. The in vitro experiments demonstrated that compounds 1 (palmatine) and 2 (fibraurin) exhibited antifungal properties. The compounds exhibited minimum inhibitory concentrations (MICs) ranging from 15.62 to 62.5 µg/mL against Candida sp. Moreover, compound 1 demonstrated a minimum fungicidal concentration (MFC) of 62.5 µg/mL against Candida glabrata and C. krusei. In contrast, compound 2 exhibited an MFC of 125 µg/mL against both Candida species. Based on a molecular docking study, it was shown that compounds 1 and 2 have a binding free energy of -6.6377 and -6.7075 kcal/mol, respectively, which indicates a strong affinity and specificity for fungal enzymatic targets. This study utilized pharmacophore modeling and Density Functional Theory (DFT) simulations to better understand the interaction dynamics and structural properties crucial for antifungal activity. The findings underscore the potential of secondary metabolites derived from A. flava to act as a foundation for creating novel and highly efficient antifungal treatments, specifically targeting fungal diseases resistant to existing treatment methods. Thus, the results regarding these compounds can provide references for the next stage in antifungal drug design. Further investigation is necessary to thoroughly evaluate these natural substances' clinical feasibility and safety characteristics, which show great potential as antifungal agents.

Purification and characterization of Cdr1, the drug-efflux pump conferring azole resistance in Candida species

Candida albicans and C. glabrata express exporters of the ATP-binding cassette (ABC) superfamily and address them to their plasma membrane to expel azole antifungals, which cancels out their action and allows the yeast to become multidrug resistant (MDR). In a way to understand this mechanism of defense, we describe the purification and characterization of Cdr1, the membrane ABC exporter mainly responsible for such phenotype in both species. Cdr1 proteins were functionally expressed in the baker yeast, tagged at their C-terminal end with either a His-tag for the glabrata version, cgCdr1-His, or a green fluorescent protein (GFP) preceded by a proteolytic cleavage site for the albicans version, caCdr1-P-GFP. A membrane Cdr1-enriched fraction was then prepared to assay several detergents and stabilizers, probing their level of extraction and the ATPase activity of the proteins as a functional marker. Immobilized metal-affinity and size-exclusion chromatographies (IMAC, SEC) were then carried out to isolate homogenous samples. Overall, our data show that although topologically and phylogenetically close, both proteins display quite distinct behaviors during the extraction and purification steps, and qualify cgCdr1 as a good candidate to characterize this type of proteins for developing future inhibitors of their azole antifungal efflux activity.

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.

Control of metalloenzyme activity using photopharmacophores

Metalloenzymes are responsible for numerous physiological and pathological processes in living organisms; however, there are very few FDA-approved metalloenzyme-targeting therapeutics (only ~ 67 FDA-approved metalloenzyme inhibitors as of 2020, less than ~ 5 % of all FDA-approved therapeutics). Most metalloenzyme inhibitors have been developed to target the catalytic metal centers in metalloenzymes via the incorporation of metal-binding groups. Light-controlled inhibition of metalloenzymes has been used as a means to specifically activate and inactivate inhibitor engagement at a desired location and time via light irradiation, allowing for precise spatiotemporal control over metalloenzyme activity. In this review, we summarize the strategies that have been employed to develop biocompatible light-sensitive inhibitors for metalloenzymes via the incorporation of different photo-activatable moieties (including photoswitchable and photocleavable groups), and the application of photo-activateable inhibitors both in vitro and in vivo. We also discuss the photophysical mechanisms of different photo-activatable groups, their action under physiological conditions, and the different modes of interaction between inhibitors and proteins (i.e., inhibition mechanisms) in the presence and absence of light. Finally, we discuss considerations for the future development of light-responsive metalloenzyme inhibitors and the challenges limiting their application in vivo.

An Insight into the Repurposing of Phytoconstituents obtained from Delhi's Aravalli Biodiversity Park as Antifungal Agents

The global prevalence of fungal infections is alarming in both the pre- and post- COVID period. Due to a limited number of antifungal drugs, there are hurdles in treatment strategies for fungal infections due to toxic potential, drug interactions, and the development of fungal resistance. All the antifungal targets (existing and newer) and pipeline molecules showing promise against these targets are reviewed. The objective was to predict or repurpose phyto-based antifungal compounds based on a dual target inhibition approach (Sterol-14-α- demethylase and HSP-90) using a case study. In pursuit of repurposing the phytochemicals as antifungal agents, a team of researchers visited Aravalli Biodiversity Park (ABP), Delhi, India, to collect information on available medicinal plants. From 45 plants, a total of 1149 ligands were collected, and virtual screening was performed using Schrodinger Suite 2016 software to get 83 hits against both the target proteins: Sterol-14-α-demethylase and HSP-90. After analysis of docking results, ligands were selected based on their interaction against both the target proteins and comparison with respective standard ligands (fluconazole and ganetespib). We have selected Isocarthamidin, Quercetin and Boeravinone B based on their docking score and binding interaction against the HSP-90 (Docking Score -9.65, -9.22 and -9.21, respectively) and 14-α-demethylase (Docking Score -9.19, -10.76 and -9.74 respectively). The docking protocol was validated and MM/GBSA studies depicted better stability of selected three ligands (Isocarthamidin, Quercetin, Boeravinone B) complex as compared to standard complex. Further, MD simulation studies were performed using the Desmond (67) software package version 2018-4. All the findings are presented as a case study for the prediction of dual targets for the repurposing of certain phytochemicals as antifungal agents.

Synthesis, antimicrobial activity and molecular docking study of benzyl functionalized benzimidazole silver(I) complexes

In this study, a series of N-functionalized benzimidazole silver(I) complexes were prepared and characterized by FT-IR, 1H, 13C{1H} NMR spectroscopy, and elemental analysis. Synthesized N-benzylbenzimidazole silver(I) complexes were evaluated for their antimicrobial activities against bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and the fungal strains Candida albicans and Candida glabrata. The results indicated that N-alkylbenzimidazole silver(I) complexes exhibited good antimicrobial activity compared to N-alkylbenzimidazole derivatives. Especially, complex 2e presented perfect antimicrobial activity than the other complexes. The characterized molecules were optimized by DFT-based calculation methods and the optimized molecules were analyzed in detail by molecular docking methods against bacterial DNA-gyrase and CYP51. The amino acid residues detected for both target molecules are consistent with expectations, and the calculated binding affinities and inhibition constants are promising for further studies. A series of N-alkylbenzimidazole silver(I) complexes were synthesized and fully characterized by means of 1H NMR, 13C NMR, and FT-IR spectroscopies. Synthesized N-alkylbenzimidazole silver(I) complexes were investigated for their antimicrobial activities against bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and the fungal strains Candida albicans and Candida glabrata. All complexes showed better activity according to Ampicilin against Pseudomonas aeruginosa. The molecules which were firstly optimized by DFT-based calculation methods were also analyzed by molecular docking methods against DNA gyrase of E. Coli and CYP51. 338 × 190 mm (96 × 96 DPI).

Polyelectrolyte-Complex-Based Hydrogel Inserts for Vaginal Delivery of Posaconazole and Probiotics

Worldwide, 40 to 50% of women suffer from reproductive tract infections. Most of these infections are mixed infections, are recurrent and difficult to treat with antimicrobials or antifungals alone. For symptomatic relief of infections, oral antimicrobial therapy must be combined with topical therapy. The purpose of this work is to optimize and develop a polyelectrolyte complex (PEC) of chitosan/anion for the formulation of posaconazole- and probiotic-loaded vaginal hydrogel inserts with prolonged release and significant mucoadhesion. PECs were prepared using chitosan as cationic and carrageenan, pectin and polycarbophil as anionic polymers via a lyophilization technique. PEC formation was confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry, by observing changes in its surface, physical and thermal properties. The probiotic, Lactobacillus casei, was added to the PEC during the lyophilization process and the effect on the probiotic viability was studied. The PECs were further compressed along with posaconazole to form hydrogel inserts and optimized using a 32 full-factorial design. The hydrogel inserts were assessed for swelling behavior, drug release, in vitro mucoadhesion and in vitro antifungal activity. The chitosan-pectin hydrogel insert demonstrated excellent mucoadhesion (1.25 N), sustained drug release (88.2 ± 2.4% in 8 h) and a swelling index of 154.7%. The efficacy of hydrogel inserts was evaluated using in vitro study with a co-culture of Lactobacillus casei and Candida albicans. This study revealed an increase in Lactobacilli casei count and a significant drop in the viable count of Candida albicans (4-log reduction in 24 h), indicating the effectiveness of hydrogel inserts in alleviating the fungal infection. Overall, our study demonstrated the potential of the hydrogel insert for preventing vaginal infection and restoring normal vaginal microbiota.

Enhancing the Antifungal Efficacy of Fluconazole with a Diterpene: Abietic Acid as a Promising Adjuvant to Combat Antifungal Resistance in Candida spp

The increasing antifungal resistance rates against conventional drugs reveal the urgent need to search for new therapeutic alternatives. In this context, natural bioactive compounds have a critical role in antifungal drug development. Since evidence demonstrates that abietic acid, a diterpene found in Pinus species, has significant antimicrobial properties, this study aimed to evaluate the antifungal activity of abietic acid against Candida spp and its ability to potentiate the activity of fluconazole. Abietic acid was tested both individually and in combination with fluconazole against Candida albicans (CA INCQS 40006), Candida krusei (CK INCQS 40095), and Candida tropicalis (CT INCQS 40042). The microdilution method was used to determine the IC50 and the cell viability curve. Minimum Fungicidal Concentration (MFC) was determined by subculture in a solid medium. The plasma membrane permeability was measured using a fluorescent SYTOX Green probe. While the IC50 of the drugs alone ranged between 1065 and 3255 μg/mL, the IC50 resulting from the combination of abietic acid and fluconazole ranged between 7563 and 160.1 μg/mL. Whether used in combination with fluconazole or isolated, abietic acid exhibited Minimum Fungicidal Concentration (MFC) values exceeding 1024 μg/mL against Candida albicans, Candida krusei and Candida tropicalis. However, it was observed that the antifungal effect of fluconazole was enhanced when used in combination with abietic acid against Candida albicans and Candida tropicalis. These findings suggest that while abietic acid alone has limited inherent antifungal activity, it can enhance the effectiveness of fluconazole, thereby reducing antifungal resistance.

Molecular Cloning, Heterologous Expression, Purification, and Evaluation of Protein-Ligand Interactions of CYP51 of Candida krusei Azole-Resistant Fungal Strain

Due to the increasing prevalence of fungal diseases caused by fungi of the genus Candida and the development of pathogen resistance to available drugs, the need to find new effective antifungal agents has increased. Azole antifungals, which are inhibitors of sterol-14α-demethylase or CYP51, have been widely used in the treatment of fungal infections over the past two decades. Of special interest is the study of C. krusei CYP51, since this fungus exhibit resistance not only to azoles, but also to other antifungal drugs and there is no available information about the ligand-binding properties of CYP51 of this pathogen. We expressed recombinant C. krusei CYP51 in E. coli cells and obtained a highly purified protein. Application of the method of spectrophotometric titration allowed us to study the interaction of C. krusei CYP51 with various ligands. In the present work, the interaction of C. krusei CYP51 with azole inhibitors, and natural and synthesized steroid derivatives was evaluated. The obtained data indicate that the resistance of C. krusei to azoles is not due to the structural features of CYP51 of this microorganism, but rather to another mechanism. Promising ligands that demonstrated sufficiently strong binding in the micromolar range to C. krusei CYP51 were identified, including compounds 99 (Kd = 1.02 ± 0.14 µM) and Ch-4 (Kd = 6.95 ± 0.80 µM). The revealed structural features of the interaction of ligands with the active site of C. krusei CYP51 can be taken into account in the further development of new selective modulators of the activity of this enzyme.

New pyrrole derivatives as DNA gyrase and 14α-demethylase inhibitors: Design, synthesis, antimicrobial evaluation, and molecular docking

An efficient one-pot reaction utilizing readily available chemical reagents was used to prepare novel 2-amino-1,5-diaryl-1H-pyrrole-3-carbonitrile derivatives and the structures of these compounds were validated by spectroscopic data and elemental analyses. All the synthetic compounds were evaluated for their antimicrobial activities (MZI assay). The tested compounds proved high activities on Staphylococcus aureus (Gram-positive bacteria) and Candida albicans (Pathogenic fungi). However, they did not show any activity on Escherichia coli (Gram-negative bacteria). The most effective compounds in MZI assay 7c, 9a, 9b, 11a, and 11b were selected to determine their MIC on S. aureus and C. albicans. Furthermore, DNA gyrase and 14-α demethylase inhibitory assays were performed to study the inhibitory activities of 7c, 9a, 9b, 11a, and 11b. The results illustrated that compound 9b was the most DNA gyrase inhibitor (IC50 of 0.0236 ± 0.45 µM, which was 1.3- fold higher than gentamicin reference IC50 values of 0.0323 ± 0.81 µM). In addition, compound 9b demonstrated the highest 14-α demethylase inhibitory effect with IC50 of 0.0013 ± 0.02 µM, compared to ketoconazole (IC50 of 0.0008 ± 0.03 µM) and fluconazole (IC50 of 0.00073 ± 0.01 µM), as antifungal reference drugs. Lastly, docking studies were performed to rationalize the dual inhibitory activities of the highly active compounds on both DNA gyrase and 14-α demethylase enzymes.

Novel antifungal triazoles with alkynyl-methoxyl side chains: Design, synthesis, and biological activity evaluation

Previous work led to the rational design, synthesis and testing of novel antifungal triazole analogues bearing alkynyl-methoxyl side chains. Tests of in vitro antifungal activity showed Candida albicans SC5314 and Candida glabrata 537 gave MIC values of ≤0.125 μg/mL for most of the compounds. Among these, compounds 16, 18, and 29 displayed broad-spectrum antifungal activity against seven human pathogenic fungal species, two fluconazole-resistant C. albicans isolates and two multi-drug resistant Candida auris isolates. Moreover, 0.5 μg/mL of 16, 18, and 29 was more effective than 2 μg/mL of fluconazole at inhibiting fungal growth of the strains tested. The most active compound (16) completely inhibited the growth of C. albicans SC5314 at 16 μg/mL for 24 h, affected biofilm formation and destroyed the mature biofilm at 64 μg/mL. Several Saccharomyces cerevisiae strains, overexpressing recombinant Cyp51s or drug efflux pumps, indicated 16, 18, and 29 targeted Cyp51 without being significantly affected by a common active site mutation, but were susceptible to target overexpression and efflux by both MFS and ABC transporters. GC-MS analysis demonstrated that 16, 18, and 29 interfered with the C. albicans ergosterol biosynthesis pathway by inhibition at Cyp51. Molecular docking studies elucidated the binding modes of 18 with Cyp51. The compounds showed low cytotoxicity, low hemolytic activity and favorable ADMT properties. Importantly, compound 16 showed potent in vivo antifungal efficacy in the G. mellonella infection model. Taken together, this study presents more effective, broad-spectrum, low toxicity triazole analogues that can contribute to the development of novel antifungal agents and help overcome antifungal resistance.

Clinical Aureobasidium Isolates Are More Fungicide Sensitive than Many Agricultural Isolates

Fungicide applications in agriculture and medicine can promote the evolution of resistant, pathogenic fungi, which is a growing problem for disease management in both settings. Nonpathogenic mycobiota are also exposed to fungicides, may become tolerant, and could turn into agricultural or medical problems, for example, due to climate change or in immunocompromised individuals. However, quantitative data about fungicide sensitivity of environmental fungi is mostly lacking. Aureobasidium species are widely distributed and frequently isolated yeast-like fungi. One species, A. pullulans, is used as a biocontrol agent, but is also encountered in clinical samples, regularly. Here, we compared 16 clinical and 30 agricultural Aureobasidium isolates based on whole-genome data and by sensitivity testing with the 3 fungicides captan, cyprodinil, and difenoconazole. Our phylogenetic analyses determined that 7 of the 16 clinical isolates did not belong to the species A. pullulans. These isolates clustered with other Aureobasidium species, including A. melanogenum, a recently separated species that expresses virulence traits that are mostly lacking in A. pullulans. Interestingly, the clinical Aureobasidium isolates were significantly more fungicide sensitive than many isolates from agricultural samples, which implies selection for fungicide tolerance of non-target fungi in agricultural ecosystems. IMPORTANCE Environmental microbiota are regularly found in clinical samples and can cause disease, in particular, in immunocompromised individuals. Organisms of the genus Aureobasidium belonging to this group are highly abundant, and some species are even described as pathogens. Many A. pullulans isolates from agricultural samples are tolerant to different fungicides, and it seems inevitable that such strains will eventually appear in the clinics. Selection for fungicide tolerance would be particularly worrisome for species A. melanogenum, which is also found in the environment and exhibits virulence traits. Based on our observation and the strains tested here, clinical Aureobasidium isolates are still fungicide sensitive. We, therefore, suggest monitoring fungicide sensitivity in species, such as A. pullulans and A. melanogenum, and to consider the development of fungicide tolerance in the evaluation process of fungicides.

Arthrocolins Synergizing with Fluconazole Inhibit Fluconazole-Resistant Candida albicans by Increasing Riboflavin Metabolism and Causing Mitochondrial Dysfunction and Autophagy

Our previous study reported that seminaturally occurring arthrocolins A to C with unprecedented carbon skeletons could restore the antifungal activity of fluconazole against fluconazole-resistant Candida albicans. Here, we showed that arthrocolins synergized with fluconazole, reducing the fluconazole minimum and dramatically augmenting the survivals of 293T human cells and nematode Caenorhabditis elegans infected with fluconazole-resistant C. albicans. Mechanistically, fluconazole can induce fungal membrane permeability to arthrocolins, leading to the intracellular arthrocolins that were critical to the antifungal activity of the combination therapy by inducing abnormal cell membranes and mitochondrial dysfunctions in the fungus. Transcriptomics and reverse transcription-quantitative PCR (qRT-PCR) analysis indicated that the intracellular arthrocolins induced the strongest upregulated genes that were involved in membrane transports while the downregulated genes were responsible for fungal pathogenesis. Moreover, riboflavin metabolism and proteasomes were the most upregulated pathways, which were accompanied by inhibition of protein biosynthesis and increased levels of reactive oxygen species (ROS), lipids, and autophagy. Our results suggested that arthrocolins should be a novel class of synergistic antifungal compounds by inducing mitochondrial dysfunctions in combination with fluconazole and provided a new perspective for the design of new bioactive antifungal compounds with potential pharmacological properties. IMPORTANCE The prevalence of antifungal-resistant Candida albicans, which is a common human fungal pathogen causing life-threatening systemic infections, has become a challenge in the treatment of fungal infections. Arthrocolins are a new type of xanthene obtained from Escherichia coli fed with a key fungal precursor toluquinol. Different from those artificially synthesized xanthenes used as important medications, arthrocolins can synergize with fluconazole against fluconazole-resistant Candida albicans. Fluconazole can induce the fungal permeability of arthrocolins into fungal cells, and then the intracellular arthrocolins exerted detrimental effects on the fungus by inducing fungal mitochondrial dysfunctions, leading to dramatically reduced fungal pathogenicity. Importantly, the combination of arthrocolins and fluconazole are effective against C. albicans in two models, including human cell line 293T and nematode Caenorhabditis elegans. Arthrocolins should be a novel class of antifungal compounds with potential pharmacological properties.

In Silico Guided Nanoformulation Strategy for Circumvention of Candida albicans Biofilm for Effective Therapy of Candidal Vulvovaginitis

Candidal vulvovaginitis involving multispecies of Candida and epithelium-bound biofilm poses a drug-resistant pharmacotherapeutic challenge. The present study aims for a disease-specific predominant causative organism resolution for the development of a tailored vaginal drug delivery system. The proposed work fabricates a luliconazole-loaded nanostructured lipid carrier-based transvaginal gel for combating Candida albicans biofilm and disease amelioration. The interaction and binding affinity of luliconazole against the proteins of C. albicans and biofilm were assessed using in silico tools. A systematic QbD analysis was followed to prepare the proposed nanogel using a modified melt emulsification-ultrasonication-gelling method. The DoE optimization was logically implemented to ascertain the effect of independent process variables (excipients concentration; sonication time) on dependent formulation responses (particle size; polydispersity index; entrapment efficiency). The optimized formulation was characterized for final product suitability. The surface morphology and dimensions were spherical and ≤300 nm, respectively. The flow behavior of an optimized nanogel (semisolid) was non-Newtonian similar to marketed preparation. The texture pattern of a nanogel was firm, consistent, and cohesive. The release kinetic model followed was Higuchi (nanogel) with a % cumulative drug release of 83.97 ± 0.69% in 48 h. The % cumulative drug permeated across a goat vaginal membrane was found to be 53.148 ± 0.62% in 8 h. The skin-safety profile was examined using a vaginal irritation model (in vivo) and histological assessments. The drug and proposed formulation(s) were checked against the pathogenic strains of C. albicans (vaginal clinical isolates) and in vitro established biofilms. The visualization of biofilms was done under a fluorescence microscope revealing mature, inhibited, and eradicated biofilm structures.

Synthesis of Benzimidazole-1,2,4-triazole Derivatives as Potential Antifungal Agents Targeting 14α-Demethylase

Invasive fungal infections (IFIs) are increasing as major infectious diseases around the world, and the limited efficacy of existing medications has resulted in substantial morbidity and death in patients due to the lack of effective antifungal agents and serious drug resistance. In this study, a series of benzimidazole-1,2,4-triazole derivatives (6a-6l) were synthesized and characterized by ¹H NMR, ¹³C NMR, and HR-MS spectral analysis. All the target compounds were screened for their in vitro antifungal activity against four fungal strains, namely, C. albicans, C. glabrata, C. krusei, and C. parapsilopsis. The synthesized compounds exhibited significant antifungal potential, especially against C. glabrata. Three compounds (6b, 6i, and 6j) showed higher antifungal activity with their MIC values (0.97 μg/mL) compared with voriconazole and fluconazole. Molecular docking provided a possible binding mode of compounds 6b, 6i, and 6j in the 14α-demethylase active site. Our studies suggested that the benzimidazole-1,2,4-triazole derivatives can be used as a new fungicidal lead targeting 14α-demethylase for further structural optimization. In addition, their effects on the L929 cell line were also investigated to evaluate the cytotoxic effects of the compounds. SEM analyses were performed to examine the effects of compounds 6a, 6i, and 6j on C. glabrata cells under in vivo experimental conditions.

The importance of selecting crystal form for triazole fungicide tebuconazole to enhance its botryticidal activity

The growing evidences of resistant fungi stimulate fully understanding tebuconazole regarding its crystal structure on fungicidal activity. In this study, the crystal structures of six technical tebuconazoles (BX, HH, JP, QZ, SJ, and YT) were characterized by using high-resolution X-ray powder diffraction and three-dimensional crystal structure modeling. A structure-activity relationship of the tebuconazoles on the susceptible (HLS and YJS) or resistant (XHR) Botrytis cinerea isolates was analyzed, the differential tricarboxylic acid (TCA) cycle metabolism was determined, and molecular docking with sterol 14α-demethylase (CYP51) was performed. The results showed that tebuconazole existed in three types of crystal forms: an overlapping-pair conformation, a side-by-side-pair conformation, and a parallel-pair conformation. QZ with the parallel-pair conformation and the minimum crystal cell volume exhibited a higher activity and a lower resistant level. XHR possessed a higher content of TCA cycle metabolites and phosphate than YJS, but the exposure to QZ significantly reduced the contents of citrate, isocitrate, α-ketoglutarate and oxaloacetate in XHR, as did the exposure to other technical tebuconazoles. Moreover, the point mutations F487L, G464S, and G443S altered the binding properties of chiral stereoscopic R-QZ with CYP51 protein. Especially the G443S mutation promoted a weak linking of R-QZ with LEU380 and TYR126, and greatly slashed the binding action at lower docking score. In conclusion, our results evidenced an efficient crystal conformation of tebuconazole to improve botryticidal activity and a potential adaptability of B. cinerea to tebuconazole inhibition in TCA cycle metabolism and CYP51 protein mutation.

Fungal Sterol Analyses by Gas Chromatography-Mass Spectrometry Using Different Derivatives

Sterols are the main components of the fungal membrane. Their study can be used to describe the chemical biodiversity among the strains and species or to work on antifungal treatment. Those molecules can be analyzed by gas chromatography coupled with mass spectrometry (GC-MS) as free molecules or after derivation as acetate or trimethylsilyl ether (TMSi). Here we describe how to extract sterols from fungal biomass according to its physiological form and the culture conditions (liquid and solid media). The different methodologies that can be used to obtain free sterols, acetate, and/or TMSi derivatives are presented. Identification keys using the fragmentation at 70 eV are also described.

Inhibitory effect and underlying mechanism of cinnamon and clove essential oils on Botryosphaeria dothidea and Colletotrichum gloeosporioides causing rots in postharvest bagging-free apple fruits

Bagging-free apple is more vulnerable to postharvest disease, which severely limits the cultivation pattern transformation of the apple industry in China. This study aimed to ascertain the dominant pathogens in postharvest bagging-free apples, to evaluate the efficacy of essential oil (EO) on inhibition of fungal growth, and to further clarify the molecular mechanism of this action. By morphological characteristics and rDNA sequence analyses, Botryosphaeria dothidea (B. dothidea) and Colletotrichum gloeosporioides (C. gloeosporioides) were identified as the main pathogens isolated from decayed bagging-free apples. Cinnamon and clove EO exhibited high inhibitory activities against mycelial growth both in vapor and contact phases under in vitro conditions. EO vapor at a concentration of 60 μL L^-1 significantly reduced the incidence and lesion diameter of inoculated decay in vivo. Observations using a scanning electron microscope (SEM) and transmission electron microscope (TEM) revealed that EO changed the mycelial morphology and cellular ultrastructure and destroyed the integrity and structure of cell membranes and major organelles. Using RNA sequencing and bioinformatics, it was demonstrated that clove EO treatment impaired the cell membrane integrity and biological function via downregulating the genes involved in the membrane component and transmembrane transport. Simultaneously, a stronger binding affinity of trans-cinnamaldehyde and eugenol with CYP51 was assessed by in silico analysis, attenuating the activity of this ergosterol synthesis enzyme. Moreover, pronounced alternations in the oxidation/reduction reaction and critical materials metabolism of clove EO-treated C. gloeosporioides were also observed from transcriptomic data. Altogether, these findings contributed novel antimicrobial cellular and molecular mechanisms of EO, suggesting its potential use as a natural and useful preservative for controlling postharvest spoilage in bagging-free apples.

Azole-Based Compounds That Are Active against Candida Biofilm: In Vitro, In Vivo and In Silico Studies

Fungal pathogens, including Candida spp., Aspergillus spp. and dermatophytes, cause more than a billion human infections every year. A large library of imidazole- and triazole-based compounds were in vitro screened for their antifungal activity against C. albicans, C. glabrata, C. krusei, A. fumigatus and dermatophytes, such as Microsporum gypseum, Trichophyton rubrum and Trichophyton mentagrophytes. The imidazole carbamate 12 emerged as the most active compound, showing a valuable antifungal activity against C. glabrata (MIC 1−16 μg/mL) and C. krusei (MIC 4−24 μg/mL). No activity against A. fumigatus or the dermatophytes was observed among all the tested compounds. The compound 12 inhibited the formation of C. albicans, C. glabrata and C. krusei biofilms and reduced the mature Candida biofilm. In the Galleria mellonella larvae, 12 showed a significant reduction in the Candida infection, together with a lack of toxicity at the concentration used to activate its antifungal activity. Moreover, the in silico prediction of the putative targets revealed that the concurrent presence of the imidazole core, the carbamate and the p-chlorophenyl is important for providing a strong affinity for lanosterol 14α-demethylase (CgCYP51a1) and the fungal carbonic anhydrase (CgNce103), the S-enantiomer being more productive in these interactions.

Antifungal properties of (2S, 4R)-Ketoconazole sulfonamide analogs

Invasive candidiasis remains a significant health concern, as it is associated with a high mortality risk. In addition, the risk of infection is significantly elevated in immunocompromised patients such as those with HIV, cancer, or those taking imcmunosuppressive drugs as a result of organ transplantation. The majority of these cases are caused by C. albicans, and C. glabrata is the second most common cause. These infections are typically treated using approved antifungal agents, but the rise of drug-resistant fungi is a serious concern. As part of our on-going effort to identify novel antifungal agents, we have studied the in vitro antifungal properties of a series of sulfonamide analogs of (2S, 4R)-Ketoconazole. Herein we report on the in vitro activity against the key fungal pathogens C. albicans, and C. glabrata.

Modulation of yeast Erg1 expression and terbinafine susceptibility by iron bioavailability

Ergosterol is a specific sterol component of yeast and fungal membranes. Its biosynthesis is one of the most effective targets for antifungal treatments. However, the emergent resistance to multiple sterol‐based antifungal drugs emphasizes the need for new therapeutic approaches. The allylamine terbinafine, which selectively inhibits squalene epoxidase Erg1 within the ergosterol biosynthetic pathway, is mainly used to treat dermatomycoses, whereas its effectiveness in other fungal infections is limited. Given that ergosterol biosynthesis depends on iron as an essential cofactor, in this report, we used the yeast Saccharomyces cerevisiae to investigate how iron bioavailability influences Erg1 expression and terbinafine susceptibility. We observed that both chemical and genetic depletion of iron decrease ERG1 expression, leading to an increase in terbinafine susceptibility. Deletion of either ROX1 transcriptional repressor or CTH1 and CTH2 post‐transcriptional repressors of ERG1 expression led to an increase in Erg1 protein levels and terbinafine resistance. On the contrary, overexpression of CTH2 led to the opposite effect, lowering Erg1 levels and increasing terbinafine susceptibility. Although strain‐specific particularities exist, opportunistic pathogenic strains of S. cerevisiae displayed a response similar to the laboratory strain. These data indicate that iron bioavailability and particular regulatory factors could be used to modulate susceptibility to terbinafine.

Antifungal activity and molecular mechanisms of mulberrin derivatives against Colletotrichum gloeosporioides for mango storage

In this work, by using high throughput virtual screening and bioactivity assays, this work revealed that three natural compounds, mulberrin (Mul) exhibiting the highest anti-CYP51 activity, isoxanthohumol and (s)-isopsoralen markedly inhibited 14α-demethylase (a pivotal biosynthetic enzyme involved in the biosynthesis of ergosterol) in Colletotrichum gloeosporioides. Results of computational biology analysis demonstrated that, among the three inhibitors bound to the catalytic pocket of CYP51, Mul showed a closer distance with heme in CYP51 and a stronger binding free energy with CYP51. In vitro tests, Mul demonstrated excellent anti-Colletotrichum gloeosporioides activity by inhibiting CYP51 activity. Notably, Mul treatment decreased the bioactivity of CYP51, thereby increasing cell membrane permeability and cell death. Moreover, Mul treatment significantly prolonged the preservation period of fruits. These results suggest that Mul suppresses anthracnose in postharvest mango by inhibiting the growth of Colletotrichum gloeosporioides and can be used as a potential natural preserving agent.

SAR analysis of heterocyclic compounds with monocyclic and bicyclic structures as antifungal agents

Infections caused by eukaryotic organisms, such as fungi, are generally more difficult to treat than bacterial infections. With the widespread use of antifungal drugs in humans and plants, resistance and toxicity have emerged. Therefore, it is desirable to develop new antifungal drugs with low toxicity that are not susceptible to the development of resistance. This review presents a summary of the past 2017 to 2021 years of research on heterocyclic compounds as antifungal agents for use in humans and plants, focusing on the structure-activity relationships (SAR) of these compounds. This review may provide ideas and data for designing and developing new antifungal drugs with fewer side effects compared with currently available drugs.

In silico Molecular Docking for assessing Anti-fungal Competency of Hydroxychavicol, a Phenolic Compound of Betel Leaf (Piper betle L.) against COVID-19 Associated Maiming Mycotic Infections

Objective: To investigate the inhibitory nature of hydroxychavicol against the Covid-19 associated mycotic infections, the present in silico study was performed in hydroxychavicol with the target Lanosterol 14 alpha demethylase and its competency was compared with four approved anti-fungal drugs. Significance: The corona virus pandemic has drawn stark lines between rich nations and poor, and the occurrence of COVID-19 associated mycotic infections, mucormycosis epidemic stands as the latest manifestation. The increase in resistance in known fungal pathogens to the available anti-fungal drugs and side effects are the important demands that forced to search anti-fungal compounds from medicinal plants as therapeutic alternatives. During the fishing expedition, Piper betle L., gets tremendous attention for its rich source of medicinally important compounds. Among them, hydroxychavicol has the enormous supportive records against microbial growth. Methods: Hydroxychavicol and the chosen drugs were retrieved from the Pubchem database and subjected to ADME analysis. The structure of the target of the chosen COVID-19 associated fungal pathogens was retrieved from PDB and unavailable protein structures were modeled using Swiss Model and validated. Virtual screening (PyRx version 0.8) was performed and the interactions were visualized using BIOVIA Discovery Studio. Results: ADME screening of hydroxychavicol was found to have clear reciprocity with the drug-likeliness nature and the subsequent molecular docking study revealed its good binding affinity towards the target protein suggesting its inhibitory nature. Conclusion: This study offers the possibility of making use of the suppressive nature of hydroxychavicol in the treatment of mycotic infections either exclusively/in synergistic approach.

Toxicity of the Pesticides Imidacloprid, Difenoconazole and Glyphosate Alone and in Binary and Ternary Mixtures to Winter Honey Bees: Effects on Survival and Antioxidative Defenses

To explain losses of bees that could occur after the winter season, we studied the effects of the insecticide imidacloprid, the herbicide glyphosate and the fungicide difenoconazole, alone and in binary and ternary mixtures, on winter honey bees orally exposed to food containing these pesticides at concentrations of 0, 0.01, 0.1, 1 and 10 µg/L. Attention was focused on bee survival, food consumption and oxidative stress. The effects on oxidative stress were assessed by determining the activity of enzymes involved in antioxidant defenses (superoxide dismutase, catalase, glutathione-S-transferase, glutathione reductase, glutathione peroxidase and glucose-6-phosphate dehydrogenase) in the head, abdomen and midgut; oxidative damage reflected by both lipid peroxidation and protein carbonylation was also evaluated. In general, no significant effect on food consumption was observed. Pesticide mixtures were more toxic than individual substances, and the highest mortalities were induced at intermediate doses of 0.1 and 1 µg/L. The toxicity was not always linked to the exposure level and the number of substances in the mixtures. Mixtures did not systematically induce synergistic effects, as antagonism, subadditivity and additivity were also observed. The tested pesticides, alone and in mixtures, triggered important, systemic oxidative stress that could largely explain pesticide toxicity to honey bees.

Characterisation of Candida parapsilosis CYP51 as a Drug Target Using Saccharomyces cerevisiae as Host

The fungal cytochrome P450 lanosterol 14α-demethylase (CYP51) is required for the biosynthesis of fungal-specific ergosterol and is the target of azole antifungal drugs. Despite proven success as a clinical target for azole antifungals, there is an urgent need to develop next-generation antifungals that target CYP51 to overcome the resistance of pathogenic fungi to existing azole drugs, toxic adverse reactions and drug interactions due to human drug-metabolizing CYPs. Candida parapsilosis is a readily transmitted opportunistic fungal pathogen that causes candidiasis in health care environments. In this study, we have characterised wild type C. parapsilosis CYP51 and its clinically significant, resistance-causing point mutation Y132F by expressing these enzymes in a Saccharomyces cerevisiae host system. In some cases, the enzymes were co-expressed with their cognate NADPH-cytochrome P450 reductase (CPR). Constitutive expression of CpCYP51 Y132F conferred a 10- to 12-fold resistance to fluconazole and voriconazole, reduced to ~6-fold resistance for the tetrazoles VT-1161 and VT-1129, but did not confer resistance to the long-tailed triazoles. Susceptibilities were unchanged in the case of CpCPR co-expression. Type II binding spectra showed tight triazole and tetrazole binding by affinity-purified recombinant CpCYP51. We report the X-ray crystal structure of ScCYP51 in complex with VT-1129 obtained at a resolution of 2.1 Å. Structural analysis of azole—enzyme interactions and functional studies of recombinant CYP51 from C. parapsilosis have improved understanding of their susceptibility to azole drugs and will help advance structure-directed antifungal discovery.