Emerging New Targets for the Treatment of Resistant Fungal Infections

Tackling multi-drug resistant fungi by efflux pump inhibitors

The emergence of multidrug-resistant fungi is of grave concern, and its infections are responsible for significant deaths among immunocompromised patients. The treatment of fungal infections primarily relies on a clinical class of antibiotics, including azoles, polyenes, echinocandins, polyketides, and a nucleotide analogue. However, the incidence of fungal infections is increasing as the treatment for human and plant fungal infections overlaps with antifungal drugs. The need for new antifungal agents acting on different targets than known targets is undeniable. Also, the pace at which loss of fungal susceptibility to antibiotics cannot be undermined. There are several modes by which fungi can develop resistance to antibiotics, including reduced drug uptake, drug target alteration, and a reduction in the cellular concentration of the drug due to active extrusions and biofilm formation. The efflux pump's overexpression in the fungi primarily reduced the antibiotic's concentration to a sub-lethal concentration, thus responsible for developing resistant fungus strains. Several strategies are used to check antibiotic resistance in multi-drug resistant fungi, including synthesizing antibiotic analogs and giving antibiotics in combination therapies. Among them, the efflux pump protein inhibitors are considered potential adjuvants to antibiotics and can block the efflux of antibiotics by inhibiting efflux pump protein transporters. Moreover, it can sensitize the antifungal drugs to multi-drug resistant fungi with overexpressed efflux pump proteins. This review discusses the natural lead molecules, repurposable drugs, and formulation strategies to overcome the efflux pump activity in the fungi.

Synthesis of novel aryl-substituted 2-aminopyridine derivatives by the cascade reaction of 1,1-enediamines with vinamidinium salts to develop novel anti-Alzheimer agents

Alzheimer's disease (AD), a severe neurodegenerative disorder, imposes socioeconomic burdens and necessitates innovative therapeutic strategies. Current therapeutic interventions are limited and underscore the need for novel inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), enzymes implicated in the pathogenesis of AD. In this study, we report a novel synthetic strategy for the generation of 2-aminopyridine derivatives via a two-component reaction converging aryl vinamidinium salts with 1,1-enediamines (EDAMs) in a dimethyl sulfoxide (DMSO) solvent system, catalyzed by triethylamine (Et3N). The protocol introduces a rapid, efficient, and scalable synthetic pathway, achieving good to excellent yields while maintaining simplistic workup procedures. Seventeen derivatives were synthesized and subsequently screened for their inhibitory activity against AChE and BChE. The most potent derivative, 3m, exhibited an IC50 value of 34.81 ± 3.71 µM against AChE and 20.66 ± 1.01 µM against BChE compared to positive control donepezil with an IC50 value of 0.079 ± 0.05 µM against AChE and 10.6 ± 2.1 µM against BChE. Also, detailed kinetic studies were undertaken to elucidate their modes of enzymatic inhibition of the most potent compounds against both AChE and BChE. The promising compound was then subjected to molecular docking and dynamics simulations, revealing significant binding affinities and favorable interaction profiles against AChE and BChE. The in silico ADMET assessments further determined the drug-like properties of 3m, suggesting it as a promising candidate for further pre-clinical development.

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.

Selenization of Small Molecule Drugs: A New Player on the Board

There is an urgent need to develop safer and more effective modalities for the treatment of a wide range of pathologies due to the increasing rates of drug resistance, undesired side effects, poor clinical outcomes, etc. Throughout the years, selenium (Se) has attracted a great deal of attention due to its important role in human health. Besides, a growing body of work has unveiled that the inclusion of Se motifs into a great number of molecules is a promising strategy for obtaining novel therapeutic agents. In the current Perspective, we have gathered the most recent literature related to the incorporation of different Se moieties into the scaffolds of a wide range of known drugs and their feasible pharmaceutical applications. In addition, we highlight different representative examples as well as provide our perspective on Se drugs and the possible future directions, promises, opportunities, and challenges of this ground-breaking area of research.

Synthesis and biological evaluation of nectriatide derivatives, potentiators of amphotericin B activity

Nectriatide 1a, a naturally occurring cyclic tetrapeptide, has been reported to a potentiator of amphotericin B (AmB) activity. In order to elucidate its structure-activity relationships, we synthesized nectriatide derivatives with different amino acids in solution-phase synthesis and evaluated AmB-potentiating activity against Candida albicans. Among them, C-and N-terminal protected linear peptides were found to show the most potent AmB-potentiating activity.

Discovery of New Tricyclic Oxime Sampangine Derivatives as Potent Antifungal Agents for the Treatment of Cryptococcosis and Candidiasis

Cryptococcus neoformans (C. neoformans) and Candida albicans (C. albicans) are classified as the critical priority groups among the pathogenic fungi, highlighting the urgent need for developing more effective antifungal therapies. On the basis of antifungal natural product sampangine, herein, a series of tricyclic oxime and oxime ether derivatives were designed. Among them, compound WZ-2 showed excellent inhibitory activity against C. neoformans (MIC80 = 0.016 μg/mL) and synergized with fluconazole to treat resistant C. albicans (FICI = 0.078). Interestingly, compound WZ-2 effectively inhibited virulence factors (e.g., capsule, biofilm, and yeast-to-hypha morphological transition), suggesting the potential to overcome drug resistance. In a mouse model of cryptococcal meningitis, compound WZ-2 (5 mg/kg) effectively reduced the brain C. neoformans H99 burden. Furthermore, compound WZ-2 alone and its combination with fluconazole also significantly reduced the kidney burden of the drug-resistant strain (0304103) and sensitive strain (SC5314) of C. albicans.

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.

SAR study of N'-(Salicylidene)heteroarenecarbohydrazides as promising antifungal agents

Clinically available antifungal drugs have therapeutic limitations due to toxicity, narrow spectrum of activity, and intrinsic or acquired drug resistance. Thus, there is an urgent need for new broad-spectrum antifungal agents with low toxicity and a novel mechanism of action. In this context, we have successfully identified several highly promising lead compounds, i.e., aromatic N'-(salicylidene)carbohydrazides, exhibiting excellent antifungal activities against Cryptococcus neoformans, Candida albicans, Aspergillus fumigatus and several other fungi both in vitro and in vivo. Building upon these highly promising results, 71 novel N'-(salicylidene)heteroarenecarbohydrazides 5 were designed, synthesized and their antifungal activities examined against fungi. Based on the SAR study, four highly promising lead compounds, i.e., 5.6a, 5.6b, 5.7b and 5.13a were identified, which exhibited excellent potency against C. neoformans, C. albicans and A. fumigatus, and displayed impressive time-kill profiles against C. neoformans with exceptionally high selectivity indices (SI ≥ 500). These four lead compounds also showed synergy with clinical antifungal drugs, fluconazole, caspofungin (CS) and amphotericin B against C. neoformans. For the SAR study, we also employed quantitative structure-activity relationship (QSAR) analysis by taking advantage of the accumulated data on a large number of aromatic and heteroaromatic N'-(salicylidene)carbohydrazides, which successfully led to rational design and selection of promising compounds for chemical synthesis and biological evaluation.

Natural phytoalexins inspired the discovery of new biphenyls as potent antifungal agents for treatment of invasive fungal infections

With the aim of discovering novel and effective antifungal agents derived from natural sources, a series of new biphenyls based on natural biphenyl phytoalexins were designed, synthesized and evaluated for their antifungal activities against four invasive fungi. By modifying the two benzene rings of noraucuparin, a well-known biphenyl phytoantitoxin, some promising compounds with remarkable antifungal activity were discovered. Notably, compounds 23a, 23e and 23h exhibited potent activities and a broad antifungal spectrum with low MICs of 0.25-16 μg/mL, which were 8-256-fold more potent than that of the lead compound noraucuparin. Particularly, they displayed comparable potency to the positive control amphotericin B against Cryptococcus neoformans. Some interesting structure-activity relationships have also been discussed. Preliminary mechanism studies revealed that compound 23h might achieve its rapid fungicidal activity by disrupting the fungal cell membrane. Moreover, compound 23h exhibited significant inhibition against some virulence factors of Cryptococcus neoformans, low toxicity to normal human cells, as well as favorable pharmacokinetic and drug-like properties. The above results evidenced that the development of new antifungal candidates derived from natural phytoalexins was a bright and promising strategy.

Novel spiro[pyrrolidine-2,3'-quinoline]-2'-one derivatives containing piperazine fragment as potential chitin synthase inhibitors and antifungal agents: Design, synthesis and biological evaluation

A series of spiro[pyrrolidine-2,3'-quinoline]-2'-one derivatives were designed and synthesized for the discovery of novel antifungal drugs. The bioactivities of all derivatives were screened by evaluating their inhibitory effects against chitin synthase (CHS) and antimicrobial activities in vitro. Enzyme inhibition experiments showed that all the synthesized compounds inhibited the chitin synthase. Compounds 4d, 4k, 4n and 4o showed inhibitory effects against CHS with IC50 values which were close to that of the control drug (polyoxin B). The results of enzyme kinetics experiment showed that these compounds were non-competitive inhibitors of chitin synthase (Ki of compound 4o is 0.14 mM). Antimicrobial experiments showed that these compounds exhibited moderate to excellent antifungal activity against pathogenic fungal strains while the compounds showed little potency against bacteria. Among them, compounds 4d, 4f, 4k and 4n showed stronger antifungal activities against C. albicans than those of fluconazole and polyoxin B. Compounds 4f, 4n and 4o showed better antifungal activities against A. flavus than those of fluconazole and polyoxin B. Compound 4d showed similar activity to that of fluconazole and stronger activity than those of polyoxin B against C. neoformans and A. fumigatus. It is also showed that these compounds have the potency against drug-resistant fungal variants. The results of sorbitol protection assay and evaluation of antifungal activity against micafungin-resistant strains experiment further illustrated that these compounds inhibited the synthesis of chitin of fungal cell wall. Drug combination experiments showed that these compounds had synergistic or additive effects when combined with fluconazole or polyoxin B. The synergistic effects with polyoxin B further confirmed the compounds were non-competitive inhibitors of chitin synthase. Additionally, docking studies showed that these compounds had strong affinity with chitin synthase from C. albicans (CaChs2). These results indicate that the target of these synthesized compounds is chitin synthase, and these compounds had excellent antifungal activity while possessed the potency against drug-resistant fungal variants.

Strategies of targeting CYP51 for IFIs therapy: Emerging prospects, opportunities and challenges

CYP51, a monooxygenase associated with the sterol synthesis pathway, is responsible for the catalysis of the 14-methyl hydroxylation reaction of lanosterol precursors. This enzyme is widely present in microorganisms, plants, and mammals. In mammals, CYP51 plays a role in cholesterol production, oligodendrocyte formation, oocyte maturation, and spermatogenesis. In fungal cells, CYP51 is an enzyme that synthesizes membrane sterols. By inhibiting fungal CYP51, ergosterol synthesis can be inhibited and ergosterol membrane fluidity is altered, resulting in fungal cell apoptosis. Thus, targeting CYP51 is a reliable antifungal strategy with important implications for the treatment of invasive fungal infections (IFIs). Many CYP51 inhibitors have been approved by the FDA for clinical treatment. However, several limitations of CYP51 inhibitors remain to be resolved, including fungal resistance, hepatotoxicity, and drug-drug interactions. New broad-spectrum, anti-resistant, highly selective CYP51 inhibitors are expected to be developed to enhance clinical efficacy and minimize adverse effects. Herein, we summarize the structural features and biological functions of CYP51 and emphatically analyze the structure-activity relationship (SAR) and therapeutic potential of different chemical types of small-molecule CYP51 inhibitors. We also discuss the latest progress of novel strategies, providing insights into new drugs targeting CYP51 for clinical practice.

Microemulsions, nanoemulsions and emulgels as carriers for antifungal antibiotics

According to estimates, up to 25% of the world's population has fungal skin diseases, making them the most prevalent infectious disease. Several chemical classes of antifungal drugs are available to treat fungal infections. However, the major challenges of conventional formulations of antifungal drugs include poor pharmacokinetic profiles like solubility, low permeability, side effects and decreased efficacy. Novel drug delivery is a promising approach for overcoming pharmacokinetic limitations and increasing the effectiveness of antibiotics. In this review, we have shed light on microemulsions, nanoemulsions, and emulgels as novel drug delivery approaches for the topical delivery of antifungal antibiotics. We believe these formulations have potential translational value and could be developed for treating fungal infections in humans.

Sertraline has fungicidal activity against Candida spp. and acts by inhibiting membrane and cell wall biosynthesis

Aim: Our study evaluated the activity of sertraline (SER) alone and associated with antifungal drugs in planktonic Candida spp. strains, and investigated its mechanism of action. Materials & methods: Broth microdilution method and minimum fungicidal concentration/MIC ratio were used to assess SER anticandidal activity, and the interaction with antifungals was determined by fractional inhibitory concentration index. The mechanism of action was investigated by flow cytometry and in silico tests. Results: SER inhibited Candida spp. strains at low concentrations by the fungicidal effect and showed no loss of effectiveness when combined. Its action seemed to be related to the membrane and cell wall biosynthesis inhibition. Conclusion: SER has activity against Candida spp. isolated and associated with antifungals, and acts by causing cell wall and membrane damage.

Novel Nitric Oxide Donor-Azole Conjugation Strategy for Efficient Treatment of Cryptococcus neoformans Infections

Invasive fungal infections (IFIs) such as cryptococcal meningitis (CM) remain a serious health issue worldwide due to drug resistance closely related to biofilm formation. Unfortunately, available antifungal drugs with ideal safety and promising potency are still lacking; thus, the research of new candidate and therapeutic approach is urgently needed. As an important gas messenger molecule, nitric oxide (NO) shows vital inhibition on various microorganism biofilms. Hence, three series of novel NO-donating azole derivatives were designed and synthesized, and the in vitro antifungal activity as well as the mechanism of action was investigated. Among them, 3a and 3e displayed excellent antifungal activity against Cryptococcus neoformans and biofilm depending on the release of NO. Moreover, a more stable analogue 3h of 3a demonstrated markedly anti-CM effects via intranasal dropping, avoiding the first-pass effects and possessing a better brain permeability bypass blood-brain barrier. These results present a promising antifungal candidate and intranasal dropping approach for the treatment of CM, warranting further studies.

Benzamidine Conjugation Converts Expelled Potential Active Agents into Antifungals against Drug-Resistant Fungi

Fungal infections present a growing global public health concern, necessitating the development of novel antifungal drugs. However, many potential antifungals, particularly the expelled potential active agents (EPAAs), are often underestimated owing to their limitations in cellular entry or expulsion by efflux pumps. Herein, we identified 68 EPAAs out of 2322 candidates with activity against a Candida albicans efflux pump-deficient strain and no inhibitory activity against the wild-type strain. Using a novel conjugation strategy involving benzamidine (BM) as a mitochondrion-targeting warhead, we successfully converted EPAAs into potent antifungals against various urgent-threat azole-resistantCandida strains. Among the obtained EPAA-BM conjugates, IS-2-BM (11) exhibited excellent antifungal activities and induced negligible drug resistance. Furthermore, IS-2-BM prevented biofilm formation, eradicated mature biofilms, and exhibited excellent therapeutic effects in a murine model of systemic candidiasis. These findings provide a promising strategy for increasing the possibilities of discovering more antifungals.

Xanthone synthetic derivatives with high anticandidal activity and positive mycostatic selectivity index values

With the current massive increases in drug-resistant microbial infection as well as the significant role of fungal infections in the death toll of COVID-19, discovering new antifungals is extremely important. Natural and synthetic xanthones are promising derivatives, although only few reports have demonstrated their antifungal mechanism of action in detail. Newly synthetized by us xanthone derivative 44 exhibited strong antifungal activity against reference and fluconazole resistant C. albicans strains. Our results indicate that the most active compounds 42 and 44 are not substrates for fungal ABC transporters (Cdr1p and Cdr2p) and Mdr1p, the main representative of the major facilitator superfamily efflux pumps, membrane proteins that are responsible for the development of resistance. Moreover, fungicidal mode of action reduces the probability of persistent or recurrent infections and resistance development. In this light, the demonstrated killing activity of the examined derivatives is their undoubted advantage. Novel synthesized compounds exhibited moderate cytotoxicity against human cell lines, although the selectivity index value for human pathogenic strains remained favourable. Our results also indicate that novel synthetized compounds 42 and 44 with antifungal activity target yeast topoisomerase II activity. In summary, further validation of xanthones applicability as antifungals is highly valuable.

Antifungal activity of cisatracurium against fluconazole-resistant Candida isolates and its antibiofilm effects

Aim: To evaluate the antifungal activity of cisatracurium against Candida spp. resistant to fluconazole strains in planktonic and biofilm forms, in addition to determining its mechanism of action. Materials & methods: Antifungal activity and pharmacological interactions were determined using broth microdilution methods and the mechanism of action was evaluated by flow cytometry and molecular docking. Results: Cisatracurium presented antifungal activity against Candida spp. planktonic cells due to alterations of mitochondrial transmembrane potential leading to cellular apoptosis in addition to interacting with important targets related to cellular respiration, membrane and cell wall evidenced by molecular docking. Furthermore, the drug both prevented biofilm formation and impaired mature biofilms. Conclusion: Cisatracurium exhibits potential antifungal activity against Candida spp.

Design, synthesis and biological evaluation of novel spiro-quinazolinone derivatives as chitin synthase inhibitors and antifungal agents

A series of spiro-quinazolinone scaffolds were constructed based on the bioactivity of quinazolinone and the inherent feature of spirocycle to design novel chitin synthase inhibitors that possess mode of action different from that of the currently used antifungal agents. Among them, the spiro[thiophen-quinazolin]-one derivatives containing α, β-unsaturated carbonyl fragments had shown inhibitory activities against chitin synthase and antifungal activities. The enzymatic experiments showed that among the sixteen compounds, compounds 12d, 12g, 12j, 12l and 12m exhibited inhibitions against chitin synthase with IC₅₀ values of 116.7 ± 19.6 μM, 106.7 ± 14.2 μM, 102.3 ± 9.6 μM, 122.7 ± 22.2 μM and 136.8 ± 12.4 μM, respectively, which were comparable to that of polyoxin B (IC₅₀ = 93.5 ± 11.1 μM). The assays of enzymatic Kinetic parameters showed that compound 12g was a non-competitive inhibitor of chitin synthase. The antifungal assays showed that compounds 12d, 12g, 12j, 12l and 12m exhibited a broad-spectrum of antifungal activity against the four strains tested in vitro. In which, compounds 12g and 12j had stronger antifungal activity against four tested strains than that of polyoxin B and similar to that of fluconazole, while compounds 12d, 12l and 12m showed antifungal activity comparable to that of polyoxin B against four tested strains. Meanwhile, compounds 12d, 12g, 12j, 12l and 12m exhibited good antifungal activity against fluconazole-resistant and micafungin-resistant fungi variants with MIC values ranging from 4 to 32 μg/mL while the MIC values of reference drugs were above 256 μg/mL. Furthermore, the results of drug-combination experiments showed that compounds 12d, 12g, 12j, 12l and 12m had synergistic or additive effects with fluconazole or polyoxin B. The results of sorbitol protection experiment and the experiment of antifungal activity against micafungin-resistant fungi further demonstrated that these compounds target chitin synthase. The result of cytotoxicity assay showed that compound 12g had low toxicity toward human lung cancer A549 cells and the ADME analysis in silico displayed that compound 12g possessed promising pharmacokinetic properties. The molecular docking indicated that compound 12g formed multiple hydrogen bond interactions binding to chitin synthase, which might be conductive to increasing the binding affinity and inhibiting the activity of chitin synthase. The above results indicated that the designed compounds were chitin synthase inhibitors with selectivity and broad-spectrum antifungal activity and could be act as the lead compounds against drug-resistant fungi.

30th Annual GP2A Medicinal Chemistry Conference

The Group for the Promotion of Pharmaceutical Chemistry in Academia (GP2A) held their 30th annual conference in August 2022 in Trinity College Dublin, Ireland. There were 9 keynote presentations, 10 early career researcher presentations and 41 poster presentations.

Controlling antifungal activity with light: Optical regulation of fungal ergosterol biosynthetic pathway with photo-responsive CYP51 inhibitors

Invasive fungal infections (IFIs) have been associated with high mortality, highlighting the urgent need for developing novel antifungal strategies. Herein the first light-responsive antifungal agents were designed by optical control of fungal ergosterol biosynthesis pathway with photocaged triazole lanosterol 14α-demethylase (CYP51) inhibitors. The photocaged triazoles completely shielded the CYP51 inhibition. The content of ergosterol in fungi before photoactivation and after photoactivation was 4.4% and 83.7%, respectively. Importantly, the shielded antifungal activity (MIC₈₀ ≥ 64 μg/mL) could be efficiently recovered (MIC₈₀ = 0.5-8 μg/mL) by light irradiation. The new chemical tools enable optical control of fungal growth arrest, morphological conversion and biofilm formation. The ability for high-precision antifungal treatment was validated by in vivo models. The light-activated compound A1 was comparable to fluconazole in prolonging survival in Galleria mellonella larvae with a median survival of 14 days and reducing fungal burden in the mouse skin infection model. Overall, this study paves the way for precise regulation of antifungal therapy with improved efficacy and safety.

Highly potent natural fungicides identified in silico against the cereal killer fungus Magnaporthe oryzae

Magnaporthe oryzae is one of the most notorious fungal pathogens that causes blast disease in cereals, and results in enormous loss of grain production. Many chemical fungicides are being used to control the pathogen but none of them are fully effective in controlling blast disease. Therefore, there is a demand for the discovery of a new natural biofungicide to manage the blast disease efficiently. A large number of new natural products showed inhibitory activities against M. oryzae in vitro. To find out effective biofungicides, we performed in silico molecular docking analysis of some of the potent natural compounds targeting four enzymes namely, scytalone dehydratase, SDH1 (PDB ID:1STD), trihydroxynaphthalene reductase, 3HNR (PDB ID:1YBV), trehalose-6-phosphate synthase, Tps1 (PDB ID:6JBI) and isocitrate lyase, ICL1 (PDB ID:5E9G) of M. oryzae fungus that regulate melanin biosynthesis and/or appresorium formation. Thirty-nine natural compounds that were previously reported to inhibit the growth of M. oryzae were subjected to rigid and flexible molecular docking against aforementioned enzymes followed by molecular dynamic simulation. The results of virtual screening showed that out of 39, eight compounds showed good binding energy with any one of the target enzymes as compared to reference commercial fungicides, azoxystrobin and strobilurin. Among the compounds, camptothecin, GKK1032A2 and chaetoviridin-A bind with more than one target enzymes of M. oryzae. All of the compounds except tricyclazole showed good bioactivity score. Taken together, our results suggest that all of the eight compounds have the potential to develop new fungicides, and remarkably, camptothecin, GKK1032A2 and chaetoviridin-A could act as multi-site mode of action fungicides against the blast fungus M. oryzae.

Network Analysis Guided Designing of Multi-Targeted Anti-Fungal Agents: Synthesis and Biological Evaluation

During the ongoing pandemic, there have been increasing reports of invasive fungal disease (IFD), particularly among immunocompromised populations. Candida albicans is one of the most common clinical pathogenic microorganisms which have become a serious health threat to population either infected with Covid-19 or on treatment with immunosuppressant's/broad-range antibiotics. Currently, benzothiazole is a well explored scaffold for anti-fungal activity, especially mercapto substituted benzothiazoles. It is reported that exploring the 2nd position of benzothiazoles yield improved anti-fungal molecules. Therefore, in the current study, lead optimization approach using bioisosteric replacement protocol was followed to improve the anti-fungal activity of an already reported benzothiazole derivative, N-(1,3-benzothiazole-2-yl)-2-(pyridine-3-ylformohydrazido) acetamide. To rationally identify the putative anti-candida targets of this derivative, network analysis was carried out. Complexes of designed compounds and identified putative targets were further analyzed for the docking interactions and their consequent retention after the completion of exhaustive MD simulations. Top seven designed compounds were synthesized and evaluated for in-vitro anti-fungal property against Candida, which indicated that compounds 1.2c and 1.2f possess improved and comparable anti-fungal activity to N-(1,3-benzothiazole-2-yl)-2-(pyridine-3-ylformohydrazido) acetamide and Nystatin, respectively.

Novel α-Aminophosphonates and α-Aminophosphonic Acids: Synthesis, Molecular Docking and Evaluation of Antifungal Activity against Scedosporium Species

The Scedosporium genus is an emerging pathogen with worldwide prevalence and high mortality rates that gives multidrug resistance to antifungals; therefore, pharmacological alternatives must be sought for the treatment of diseases caused by this fungus. In the present project, six new α-aminophosphates were synthesized by the Kabachnik–Fields multicomponent reaction by vortex agitation, and six new monohydrolyzed α-aminophosphonic acids were synthesized by an alkaline hydrolysis reaction. Antifungal activity was evaluated using the agar diffusion method as an initial screening to determine the most active compound compared to voriconazole; then it was evaluated against 23 strains of the genus Scedosporium following the M38-A2 protocol from CLSI (activity range: 648.76–700 µg/mL). Results showed that compound 5f exhibited the highest antifungal activity according to the agar diffusion method (≤1 mg/mL). Cytotoxicity against healthy COS-7 cells was also evaluated by the MTT assay and it was shown that compound 5f exhibits a lower toxicity in comparison to voriconazole at the same concentration (1000 µM). A docking study was conducted afterwards, showing that the possible mechanism of action of the compound is through the inhibition of allosteric 14-α-demethylase. Taking these results as a basis, 5f is presented as a compound with attractive properties for further studies.

Role of Azole Drugs in Promoting Fungal Cell Autophagy Revealed by an NIR Fluorescence-Based Theranostic Probe

Autophagy, a widespread degradation system in eukaryotes, plays an important role in maintaining the homeostasis of the cellular environment and the recycling of substances. Optical probes for the tracking of autophagy can be used as an effective tool not only to visualize the autophagy process but also to study autophagy-targeted drugs. Various molecule probes for autophagy of cancer cells emerge but are very limited for that of fungal cells, resulting in the lack of research on antifungal drugs targeting autophagy. To address this issue, we report an azole NIR fluorescence-based theranostic probe AF-1 with antifungal activity that is sensitive to autophagy-associated pH. The unique design of this probe lies in the introduction of both the pH-sensitive fluorophore with a detection range matching the pH range of the autophagy process and the conserved core structural fragment of azole drugs, providing a strategy to investigate the relationship between antifungal drug action and autophagy. As such, AF-1 exhibited excellent spectral properties and was found to target and induce the autophagy of the fungal cell membrane while maintaining moderate antifungal activity. Of note, using this theranostic probe as both a dye and drug, the autophagy process of fungi was visualized in a ratiometric manner, revealing the role of azole antifungal drugs in promoting autophagy to induce fungal cell apoptosis.

Highly Active Small Aminated Quinolinequinones against Drug-Resistant Staphylococcus aureus and Candida albicans

Two subseries of aminated quinolinequinones (AQQs, AQQ1-16) containing electron-withdrawing group (EWG) or electron-donating group (EDG) in aryl amine moiety were successfully synthesized. Antimicrobial activity assessment indicates that some of the AQQs (AQQ8-10 and AQQ12-14) with an EDG in aryl amine exhibited strong antibacterial activity against Gram-positive bacterial strains, including Staphylococcus aureus (ATCC^® 29213) and Enterococcus faecalis (ATCC^® 29212). In contrast, AQQ4 with an EWG in aryl amine displayed excellent antifungal activity against fungi Candida albicans (ATCC^® 10231) with a MIC value of 1.22 μg/mL. To explore the mode of action, the selected AQQs (AQQ4 and AQQ9) were further evaluated in vitro to determine their antimicrobial activity against each of 20 clinically obtained resistant strains of Gram-positive bacteria by performing antibiofilm activity assay and time-kill curve assay. In addition, in silico studies were carried out to determine the possible mechanism of action observed in vitro. The data obtained from these experiments suggests that these molecules could be used to target pathogens in different modes of growth, such as planktonic and biofilm.

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.

Polyenes in Medium Chain Length Polyhydroxyalkanoate (mcl-PHA) Biopolymer Microspheres with Reduced Toxicity and Improved Therapeutic Effect against Candida Infection in Zebrafish Model

Immobilizing antifungal polyenes such as nystatin (Nys) and amphotericin B (AmB) into biodegradable formulations is advantageous compared to free drug administration providing sustained release, reduced dosing due to localized targeting and overall reduced systemic drug toxicity. In this study, we encapsulated Nys and AmB in medium chain length polyhydroxyalkanoates (mcl-PHA) microspheres (7–8 µm in diameter). The obtained formulations have been validated for antifungal activity in vitro against a panel of pathogenic fungi including species of Candida, Aspergillus, Microsporum and Trichophyton genera and toxicity and efficacy in vivo using the zebrafish model of disseminated candidiasis. While free polyenes, especially AmB, were highly toxic to zebrafish embryos at the effective (MIC) doses, after their loading into mcl-PHA microspheres, inner organ toxicity and teratogenicity associated with both drugs were not observed, even at 100 × MIC doses. The obtained mcl-PHA/polyene formulations have successfully eradicated C. albicans infection and showed an improved therapeutic profile in zebrafish by enhancing infected embryos survival. This approach is contributing to the antifungal arsenal as polyenes, although the first broad-spectrum antifungals on the market are still the gold standard for treatment of fungal infections.

Species-Selective Targeting of Fungal Hsp90: Design, Synthesis, and Evaluation of Novel 4,5-Diarylisoxazole Derivatives for the Combination Treatment of Azole-Resistant Candidiasis

Invasive fungal infections are emerging as serious infectious diseases worldwide. Because of the development of antifungal drug resistance, the limited efficacy of the existing drugs has led to high mortality in patients. The use of the essential eukaryotic chaperone Hsp90, which plays a multifaceted role in drug resistance across diverse pathogenic fungal species, is considered to be a new strategy to mitigate the resistance and counter the threat posed by drug-resistant fungi. Thus, a series of 4,5-diarylisoxazole analogues as fungal Hsp90 inhibitors were designed and synthesized that had potent synergistic effects with fluconazole in vitro and in vivo. In particular, compound A17 could avoid the potential mammalian toxicity of Hsp90 inhibitors based on key reside differences between humans and fungi. These data support the feasibility of targeting fungal Hsp90 as a promising antifungal strategy and further development of compound A17 as a valuable research probe for the investigation of fungal Hsp90.

Structure-Guided Discovery of the Novel Covalent Allosteric Site and Covalent Inhibitors of Fructose-1,6-Bisphosphate Aldolase to Overcome the Azole Resistance of Candidiasis

Fructose-1,6-bisphosphate aldolase (FBA) represents an attractive new antifungal target. Here, we employed a structure-based optimization strategy to discover a novel covalent binding site (C292 site) and the first-in-class covalent allosteric inhibitors of FBA from Candida albicans (CaFBA). Site-directed mutagenesis, liquid chromatography-mass spectrometry, and the crystallographic structures of APO-CaFBA, CaFBA-G3P, and C157S-2a4 revealed that S268 is an essential pharmacophore for the catalytic activity of CaFBA, and L288 is an allosteric regulation switch for CaFBA. Furthermore, most of the CaFBA covalent inhibitors exhibited good inhibitory activity against azole-resistant C. albicans, and compound 2a11 can inhibit the growth of azole-resistant strains 103 with the MIC₈₀ of 1 μg/mL. Collectively, this work identifies a new covalent allosteric site of CaFBA and discovers the first generation of covalent inhibitors for fungal FBA with potent inhibitory activity against resistant fungi, establishing a structural foundation and providing a promising strategy for the design of potent antifungal drugs.

Design, synthesis, and biological activity evaluation of 2-(benzo[b]thiophen-2-yl)-4-phenyl-4,5-dihydrooxazole derivatives as broad-spectrum antifungal agents

To discover antifungal compounds with broad-spectrum and stable metabolism, a series of 2-(benzo[b]thiophen-2-yl)-4-phenyl-4,5-dihydrooxazole derivatives was designed and synthesized. Compounds A30-A34 exhibited excellent broad-spectrum antifungal activity against Candida albicans with MIC values in the range of 0.03-0.5 μg/mL, and against Cryptococcus neoformans and Aspergillus fumigatus with MIC values in the range of 0.25-2 μg/mL. In addition, compounds A31 and A33 showed high metabolic stability in human liver microsomes in vitro, with the half-life of 80.5 min and 69.4 min, respectively. Moreover, compounds A31 and A33 showed weak or almost no inhibitory effect on the CYP3A4 and CYP2D6. The pharmacokinetic evaluation in SD rats showed that compound A31 had suitable pharmacokinetic properties and was worthy of further study.

Broadening antifungal spectrum and improving metabolic stablity based on a scaffold strategy: Design, synthesis, and evaluation of novel 4-phenyl-4,5-dihydrooxazole derivatives as potent fungistatic and fungicidal reagents

5-phenylthiophene derivatives exhibited excellent antifungal activity against Candida albicans, Candida tropicalis and Cryptococcus neoformans. However, optimal compound 7 was inactive against Aspergillus fumigatus and unstable in human liver microsomes in vitro with a half-life of 18.6 min. To discover antifungal agents with a broad spectrum and improve the metabolic properties of the compounds, the scaffold hopping strategy was adopted and a series of 4-phenyl-4,5-dihydrooxazole derivatives were designed and synthesized. It was especially encouraging that compound 22a displayed significant antifungal activities against eight susceptible strains and seven FLC-resistant strains. Furthermore, the potent compound 22a could prevent the formation of fungalbiofilms and displayed satisfactory fungicidal activity. In addition, the metabolic stability of compound 22a was improved significantly, with the half-life of 70.5 min. Compound 22a was almost nontoxic to mammalian A549, MCF-7, HepG2, and 293T cells. Moreover, pharmacokinetic studies in SD rats showed that compound 22a exhibited pharmacokinetic properties with a bioavailability of 15.22% and a half-life of 4.44 h, indicating that compound 22a is worthy of further study.

Natural and synthetic β-carboline as a privileged antifungal scaffolds

The discovery of antifungal agents with novel structure, broad-spectrum, low toxicity, and high efficiency has been the focus of medicinal chemists. Over the past decades, β-carboline scaffold has attracted extensive attention in the scientific community due to its potent and diverse biological activities with nine successfully marketed β-carboline-based drugs. In this review, we summarized the current states and advances in the antifungal activity of natural and synthetic β-carbolines. Additionally, the structure-activity relationships and their antifungal mechanisms targeting biofilm, cell wall, cell membrane, and fungal intracellular targets were also systematically discussed. In summary, β-carbolines have the great potential to develop new efficient scaffolds to combat fungal infections.

Characterization and cytotoxicity assessment of biosurfactant derived from Lactobacillus pentosus NCIM 2912

Noteworthy properties of biosurfactant (BS) are fascinating scientific fraternity to explore them for food, medicinal, cosmetic, or pharmaceutical etc. applications. Newer products intended for pharmaceutical purposes are mandatory to go through pragmatic evaluation protocols. BS, being less cytotoxic, offers an ideal candidature for widespread applications in the healthcare sector. The goal of the current study was the isolation, physico-chemical characterization, and safety assessment of cell-associated biosurfactant (CABS) from Lactobacillus pentosus NCIM 2912. The culture was grown in a 3-L fermentor to produce CABS from the cell pellets through procedures like centrifugation, filtration, dialysis, column chromatography, and freeze-drying. Further, physical properties like surface tension (ST), critical micelle concentration (CMC), contact angle (CA), emulsification activity, stability of emulsion (height of emulsion, the extent of coalescence, and appearance), and ionic character of CABS were evaluated. Analytical characterization through TLC, FTIR, NMR, and GC-MS was carried out. The physico-chemical characterization revealed CABS as an anionic, multicomponent glycolipopeptide having a hydrophobic chain comprising butanoic acid (C4), decanoic acid (C10), undecanoic acid (C11), tridecanoic acid (C13), hexadecenoic acid (C16), and octadecanoic acid (C18). The oil-in-water (O/W) emulsions formed by CABS with various oils (olive, sesame, soybean, coconut) were stabilized up to the 7th day of storage and were analogous with polysorbate 80 (emulsifier/defoamer used in food industries). The O/W emulsions are quite stable at room temperature with no evidence of coalescence of droplets around 1 week. The cytotoxicity of CABS was evaluated through MTT (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide) assay. Cytotoxicity study performed on the human embryonic kidney (HEK 293), mouse fibroblast ATCC L929 and human epithelial type (HEP-2) cell lines recorded viability of 90.3 ± 0.1%, 99.2 ± 0.43, and 94.3 ± 0.2% respectively. The toxicity of the BS was comparable to that of the commercially used rhamnolipid sample. Thus, CABS derived from L. pentosus NCIM 2912 pose promising applications in the pharmaceutical, food industries acquiescently. The multifunctional potential of the incredibly versatile microbial product like BS from lactic acid bacteria (LAB) certainly contributes to wider avenues for varied industries.

The Influence of Tea Tree Oil on Antifungal Activity and Pharmaceutical Characteristics of Pluronic® F-127 Gel Formulations with Ketoconazole

Fungal skin infections are currently a major clinical problem due to their increased occurrence and drug resistance. The treatment of fungal skin infections is based on monotherapy or polytherapy using the synergy of the therapeutic substances. Tea tree oil (TTO) may be a valuable addition to the traditional antifungal drugs due to its antifungal and anti-inflammatory activity. Ketoconazole (KTZ) is an imidazole antifungal agent commonly used as a treatment for dermatological fungal infections. The use of hydrogels and organogel-based formulations has been increasing for the past few years, due to the easy method of preparation and long-term stability of the product. Therefore, the purpose of this study was to design and characterize different types of Pluronic^® F-127 gel formulations containing KTZ and TTO as local delivery systems that can be applied in cases of skin fungal infections. The influence of TTO addition on the textural, rheological, and bioadhesive properties of the designed formulations was examined. Moreover, the in vitro release of KTZ, its permeation through artificial skin, and antifungal activity by the agar diffusion method were performed. It was found that obtained gel formulations were non-Newtonian systems, showing a shear-thinning behaviour and thixotropic properties with adequate textural features such as hardness, compressibility, and adhesiveness. Furthermore, the designed preparations with TTO were characterized by beneficial bioadhesive properties. The presence of TTO improved the penetration and retention of KTZ through the artificial skin membrane and this effect was particularly visible in hydrogel formulation. The developed gels containing TTO can be considered as favourable formulations in terms of drug release and antifungal activity.

Evaluation of the antifungal photodynamic activity of Thymophylla pentachaeta extracts against Candida albicans and its virulence factors

BACKGROUND

Candida albicans is one of the most common causative of opportunistic infections. Treatment of candidiasis is challenging considering the few antifungal drugs available and the increase in resistance. Antimicrobial photodynamic therapy (aPDT) is a recently developed therapeutic option that combines a non-toxic photosensitizer (PS) and light to kill the microbial pathogens. Targeting virulence, defined as the ability of a pathogen to cause overt disease, represents another attractive target for the development of novel antifungal agents. Thymophylla pentachaeta (DC.) Small var. belenidium (DC.) is an endemic plant from Argentina in which the presence of thiophenes, biologically active compounds whose antifungal activity is enhanced by irradiation with Ultraviolet A (UVA), have been already described.

PURPOSE

The purpose of this study was to evaluate the photodynamic antifungal activity of hexane (Hex), dichloromethane (DCM), ethyl acetate (EtOAc) and methanol (MeOH) extracts from T. pentachaeta var. belenidium and their inhibitory effects on C. albicans virulence factors as well as biofilm formation and eradication.

STUDY DESIGN/METHODS

Antifungal photodynamic activity of Hex, DCM, EtOAc and MeOH extracts from different parts of the plant were assessed with the microbroth dilution, bioautography and the time-kill assays, under light and darkness conditions. The capacities of the most active extracts of inhibiting Candida virulence factors (adherence to epithelial cells, germ tube and pseudomycelium formation and hydrolytic enzyme secretion) were assessed. In addition, the activity against biofilm formation and eradication has been investigated by reaction with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) that quantifies living cells in these structures.

RESULTS

Hex and DCM extracts from T. pentachaeta roots exhibited high photodynamic antifungal activity against C. albicans [Minimal fungicide concentrations (MFCs)= 7.8 µg/ml] under UVA light irradiation. Chemical analysis of active extracts (Hex and DCM from roots) revealed the presence of photoactive thiophenes. Both extracts generate reactive oxygen species through type I and II mechanisms. These extracts, at sub-inhibitory concentrations, under light conditions decreased the adherence of C. albicans to Buccal Epithelial Cells (BEC), inhibited germ tube formation and reduced esterase production. Finally, they demonstrated activity against preformed biofilms submitted to irradiation (MFCs= 3.91 µg/ml and 15.63 µg/ml for Hex and DCM extracts, respectively).

CONCLUSION

Taking together, results demonstrated the strong photodynamic effects of T. pentachaeta root extracts under UVA irradiation, making them valuable alternatives to the already established antifungal drugs against C. albicans.

Updated Information on Antimicrobial Activity of Hydrazide-Hydrazones

Hydrazide-hydrazones possess a wide spectrum of bioactivity, including antibacterial, antitubercular, antifungal, anticancer, anti-inflammatory, anticonvulsant, antidepressant, antiviral, and antiprotozoal properties. This review is focused on the latest scientific reports regarding antibacterial, antimycobacterial, and antifungal activities of hydrazide-hydrazones published between 2017 and 2021. The molecules and their chemical structures presented in this article are the most active derivatives, with discussed activities having a hydrazide-hydrazone moiety as the main scaffold or as a side chain. Presented information constitute a concise summary, which may be used as a practical guide for further design of new molecules with antimicrobial activity.

Discovery of 1,2,3-selenadiazole analogues as antifungal agents using a scaffold hopping approach

With the increasing incidence of antifungal resistance, new antifungal agents having novel scaffolds hence are in an urgent need to combat infectious diseases caused by multidrug-resistant (MDR) pathogens. In this study, we reported the design, synthesis, and pharmacological evaluation of novel 1,2,3-selenadiazole analogues by scaffold hopping strategy. Preliminary results of antifungal activity demonstrated that the new class of compounds showed broad-spectrum fungistatic and fungicidal activity. Most importantly, these newly synthesized compounds can eliminate these azole-resistant fungi and inhibit the formation of C. albicans biofilm. In particular, compound S07 showed promising antifungal activity against five azole-resistant strains with MIC values ranging from 4 to 32 μg/mL. Then, further target identification and mechanistic studies indicated that representative compound S07 exert its inhibitory activity by inhibiting fungal lanosterol 14α-demethylase enzyme (CYP51). Interestingly, representative compounds showed low cytotoxicity on mammalian cell lines. In addition, the molecular docking studies elucidated the binding modes of these compounds toward CYP51. Altogether, these results suggest that compound S07 with novel skeleton is a promising CYP51 inhibitor for treatment of fungal infections.

Identification of Thiazoyl Guanidine Derivatives as Novel Antifungal Agents Inhibiting Ergosterol Biosynthesis for Treatment of Invasive Fungal Infections

Invasive fungal infections (IFIs) are fatal infections, but treatment options are limited. The clinical efficacies of existing drugs are unsatisfactory because of side effects, drug-drug interaction, unfavorable pharmacokinetic profiles, and emerging drug-resistant fungi. Therefore, the development of antifungal drugs with a new mechanism is an urgent issue. Herein, we report novel aryl guanidine antifungal agents, which inhibit a novel target enzyme in the ergosterol biosynthesis pathway. Structure-activity relationship development and property optimization by reducing lipophilicity led to the discovery of 6h, which showed potent antifungal activity against Aspergillus fumigatus in the presence of serum, improved metabolic stability, and PK properties. In the murine systemic A. fumigatus infection model, 6h exhibited antifungal efficacy equivalent to voriconazole (1e). Furthermore, owing to the inhibition of a novel target in the ergosterol biosynthesis pathway, 6h showed antifungal activity against azole-resistant A. fumigatus.

Molecular targets for antifungals in amino acid and protein biosynthetic pathways

Fungi cause death of over 1.5 million people every year, while cutaneous mycoses are among the most common infections in the world. Mycoses vary greatly in severity, there are long-term skin (ringworm), nail or hair infections (tinea capitis), recurrent like vaginal candidiasis or severe, life-threatening systemic, multiorgan infections. In the last few years, increasing importance is attached to the health and economic problems caused by fungal pathogens. There is a growing need for improvement of the availability of antifungal drugs, decreasing their prices and reducing side effects. Searching for novel approaches in this respect, amino acid and protein biosynthesis pathways appear to be competitive. The route that leads from amino acid biosynthesis to protein folding and its activation is rich in enzymes that are descriptive of fungi. Blocking the action of those enzymes often leads to avirulence or growth inhibition. In this review, we want to trace the principal processes of fungi vitality. We present the data of genes encoding enzymes involved in amino acid and protein biosynthesis, potential molecular targets in antifungal chemotherapy, and describe the impact of inhibitors on fungal organisms.

Cellular and non-target metabolomics approaches to understand the antifungal activity of methylaervine against Fusarium solani

Botanical fungicides are promising replacements for pure chemical synthetic pesticides in agriculture and organic food production. Methylaervine with good physicochemical properties exhibited effective activity against F. solani (EC₅₀ = 10.56 µM) better than the positive control thiophanate-methyl (EC₅₀ = 27.94 µM). The activity changes of malondialdehyde (MDA), catalase (CAT) and superoxide dismutase (SOD) showed that methylaervine could significantly induce lipid peroxidation and activate the antioxidant enzymes. According to the metabolomics analysis, fifty-one differential metabolites and two major antifungal-related pathways covering tricarboxylic acid (TCA) cycle and steroid biosynthesis were identified. Moreover, the disturbance for TCA cycle was validated by the activity changes of dehydrogenase (MDH) and succinate dehydrogenase (SDH) as well as docking simulation. Homology modeling and docking study revealed that hydrogen bonds and hydrophobic interactions played a vital role in methylaervine-protein stability. This study provided new insight into the antifungal activity of methylaervine, which is important for the development of novel botanical fungicides based on methylaervine.

Lead optimization generates selenium-containing miconazole CYP51 inhibitors with improved pharmacological profile for the treatment of fungal infections

A series of selenium-containing miconazole derivatives were identified as potent antifungal drugs in our previous study. Representative compound A03 (MIC = 0.01 μg/mL against C.alb. 5314) proved efficacious in inhibiting the growth of fungal pathogens. However, further study showed lead compound A03 exhibited potential hemolysis, significant cytotoxic effect and unfavorable metabolic stability and was therefore modified to overcome these drawbacks. In this article, the further optimization of selenium-containing miconazole derivatives resulted in the discovery of similarly potent compound B17 (MIC = 0.02 μg/mL against C.alb. 5314), exhibiting a superior pharmacological profile with decreased rate of metabolism, cytotoxic effect and hemolysis. Furthermore, compound B17 showed fungicidal activity against Candida albicans and significant effects on the treatment of resistant Candida albicans infections. Meanwhile, compound B17 not only could reduce the ergosterol biosynthesis pathway by inhibiting CYP51, but also inhibited biofilm formation. More importantly, compound B17 also shows promising in vivo efficacy after intraperitoneal injection and the PK study of compound B17 was evaluated. In addition, molecular docking studies provide a model for the interaction between the compound B17 and the CYP51 protein. Overall, we believe that these selenium-containing miconazole compounds can be further developed for the potential treatment of fungal infections.

Synthesis of New Bis-pyrazolines Endowed with Potent Antifungal Activity against Candida albicans and Aspergillus niger

Background:

Due to the increasing number of cases of invasive fungal infections (IFIs), there is an urgent need to identify potent antifungal agents capable of combating IFIs. Pyrazolines are one such class of therapeutically active agents that could be considered to fulfill this need.

Objective:

In this context, this paper aims to identify two new series of bis-pyrazolines endowed with potent antifungal activity against Candida albicans and Aspergillus niger.

Methods:

Two new series of bis-pyrazolines (4a-i, 5a-e) were synthesized through an efficient and versatile synthetic procedure. The compounds were screened for their antifungal effects on C. albicans and A. niger using a broth microdilution method. Their cytotoxic effects on NIH/3T3 mouse embryonic fibroblast cells were determined using MTT assay. Molecular docking studies were performed in the active site of lanosterol 14α-demethylase (CYP51) to shed light on their antifungal effects using Schrödinger’s Maestro molecular modeling package.

Results:

5,5'-(1,4-Phenylene)bis[1-(2-(5-phenyl-1,3,4-oxadiazol-2-yl)thio)acetyl)-3-(2-thienyl)-4,5- dihydro-1H-pyrazole] (4a) and 5,5'-(1,4-phenylene)bis[1-(2-(4-(2-hydroxyethyl)-1-piperazinylthiocarbamoyl) thio)acetyl)-3-(2-thienyl)-4,5-dihydro-1H-pyrazole] (5a) were found as the most promising antifungal agents in this series. Compounds 4a and 5a showed pronounced antifungal activity against C. albicans (MIC= 0.016 mg/mL) and A. niger (MIC= 0.008 mg/mL). Based on MTT assay, their antifungal effects were selective (IC50 > 0.500 mg/mL for NIH/3T3 cell line). Molecular docking studies suggested that compounds 5a-e might show their anticandidal effects via CYP51 inhibition in regard to their stronger interactions in the active site of CYP51.

Conclusion:

Compounds 4a and 5a stand out as potential antifungal agents for the management of IFIs caused by C. albicans and A. niger.