From antidiabetic to antifungal: discovery of highly potent triazole-thiazolidinedione hybrids as novel antifungal agents

Antifungal efficacy of imidazo[1,2-a]pyrazine-based thiosemicarbazones and thiazolidinediones against Sporothrix species

Aim: To evaluate antifungal potential of 5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine hybrids based on thiosemicarbazones and thiazolidinediones against pathogenic Sporothrix species. Methods: Antifungal activity of nine compounds were assessed by broth microdilution. Interactions between active compounds and itraconazole were evaluated by the checkerboard assay using non-wild-type isolates. Cytotoxicity of the compounds was determined. Results: Four C-3 substituted analogs showed antifungal activity, unrelated to thiosemicarbazone or thiazolidinedione functions. Synergistic interactions between the four compounds and itraconazole, and low toxicity on mouse fibroblast cells were observed. Activity of 5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine hybrids against Sporothrix depended on the substitution on the imidazopyrazine ring. Conclusion: Antifungal potential, overcoming itraconazole resistance and low toxicity indicate the possible use of that series of compounds in a therapeutic alternative for treatment of sporotrichosis.

Rational Design of New Monoterpene-Containing Azoles and Their Antifungal Activity

Azole antifungals, including fluconazole, have long been the first-line antifungal agents in the fight against fungal infections. The emergence of drug-resistant strains and the associated increase in mortality from systemic mycoses has prompted the development of new agents based on azoles. We reported a synthesis of novel monoterpene-containing azoles with high antifungal activity and low cytotoxicity. These hybrids demonstrated broad-spectrum activity against all tested fungal strains, with excellent minimum inhibitory concentration (MIC) values against both fluconazole-susceptible and fluconazole-resistant strains of Candida spp. Compounds 10a and 10c with cuminyl and pinenyl fragments demonstrated up to 100 times lower MICs than fluconazole against clinical isolates. The results indicated that the monoterpene-containing azoles had much lower MICs against fluconazole-resistant clinical isolates of Candida parapsilosis than their phenyl-containing counterpart. In addition, the compounds did not exhibit cytotoxicity at active concentrations in the MTT assay, indicating potential for further development as antifungal agents.

New Antifungal Agents with Azole Moieties

Fungal conditions affect a multitude of people worldwide, leading to increased hospitalization and mortality rates, and the need for novel antifungals is emerging with the rise of resistance and immunocompromised patients. Continuous use of azole drugs, which act by inhibiting the fungal CYP51, involved in the synthesis of ergosterol, essential to the fungal cell membrane, has enhanced the resistance and tolerance of some fungal strains to treatment, thereby limiting the arsenal of available drugs. The goal of this review is to gather literature information on new promising azole developments in clinical trials, with in vitro and in vivo results against fungal strains, and complementary assays, such as toxicity, susceptibility assays, docking studies, among others. Several molecules are reviewed as novel azole structures in clinical trials and with recent/imminent approvals, as well as other innovative molecules with promising antifungal activity. Structure-activity relationship (SAR) studies are displayed whenever possible. The azole moiety is brought over as a privileged structure, with multiple different compounds emerging with distinct pharmacophores and SAR. Particularly, 1,2,3-triazole natural product conjugates emerged in the last years, presenting promising antifungal activity and a broad spectrum against various fungi.

Thiazolidinedione-Based Structure Modification of Celastrol Provides Thiazolidinedione-Conjugated Derivatives as Potent Agents against Non-Small-Cell Lung Cancer Cells through a Mitochondria-Mediated Apoptotic Pathway

In order to improve the potential of celastrol against non-small-cell lung cancer cells, the privileged structure, thiazolidinedione, was introduced into its C-20 carboxylic group with acetylpiperazine as a linker, and the thiazolidinedione-conjugated compounds 10a-10t were prepared. The target compounds were evaluated for their cytotoxic activities against the A549 cell line, and the results showed that most of the compounds 10a-10t displayed improved potency over celastrol, and compound 10b exhibited significant activity against the A549 cell line, with an IC₅₀ value of 0.08 μM, which was 13.8-fold more potent than celastrol (IC₅₀ = 1.10 μM). The mechanistic studies suggested that 10b could induce A549 cell apoptosis, as evidenced by Hoechst 33342 staining and annexin V-FITC/propidium iodide dual staining assays. Western blot analysis suggested that compound 10b could upregulate Bax expression, downregulate Bcl-2 expression, and activate the mitochondria-mediated apoptotic pathway. Furthermore, compound 10b could effectively inhibit tumor growth when tested in an A549 cell xenograft mouse model. Collectively, compound 10b is worthy of further investigation to support the discovery of effective agents against non-small-cell lung cancer.

Mechanisms of Candida Resistance to Antimycotics and Promising Ways to Overcome It: The Role of Probiotics

Pathogenic Candida and infections caused by those species are now considered as a serious threat to public health. The treatment of candidiasis is significantly complicated by the increasing resistance of pathogenic strains to current treatments and the stagnant development of new antimycotic drugs. Many species, such as Candida auris, have a wide range of resistance mechanisms. Among the currently used synthetic and semi-synthetic antifungal drugs, the most effective are azoles, echinocandins, polyenes, nucleotide analogs, and their combinations. However, the use of probiotic microorganisms and/or the compounds they produce is quite promising, although underestimated by modern pharmacology, to control the spread of pathogenic Candida species.

An Insight into the Synthesis and SAR of 2,4-Thiazolidinediones (2,4-TZD) as Multifunctional Scaffold: A Review

2,4-Thiazolidinedione (2,4-TZD) is a versatile pharmacophore, a privileged scaffold, and a remarkable sulphur-containing heterocyclic compound with diverse pharmacological activities. The multifarious biological activities, due to different mechanisms of action, low cost, and easy availability of 2,4-TZD impressed medicinal chemists to integrate this moiety to develop various lead compounds with diverse therapeutic actions. This resulted in the swift development in the last decade for generating different new potential molecules bearing 2,4-TZD. In this review, the authors attempt to shape and present the latest investigations (2012 onwards) going on in generating promising 2,4-TZD containing lead compounds. The data has been collected and analyzed to develop the structure-activity relationship (SAR). The SAR and active pharmacophores of various leads accountable for antidiabetic, anticancer, antimicrobial, and antioxidant activities have also been illustrated. This review also highlighted some of the important chemical synthetic routes for the preparation of various 2,4-TZD derivatives. This review will definitely serve as a useful source of structural information to medicinal chemists and may be utilized for the strategic design of potent 2,4-TZD derivatives in the future.

Synthesis, Anticancer, and Antibacterial Studies of Benzylidene Bearing 5-substituted and 3,5-disubstituted-2,4-Thiazolidinedione Derivatives

AIM

To develop novel compounds having potent anticancer and antibacterial activities.

BACKGROUND

Several studies have proved that benzylidene analogues of clinical 2,4-TZDs, such as troglitazone and ciglitazone, have more potent antiproliferative activity than their parent compounds. Literature studies also revealed that the attachment of more heterocyclic rings, containing nitrogen on 5th position of 2,4-TZD, can enhance the antimicrobial activity. Hence, attachment of various moieties on the benzylidene ring may produce safe and effective compounds in the future.

OBJECTIVE

The objective of the present study was to synthesize a set of novel benzylidene ring containing 5- and 3-substituted-2,4-thiazolidinedione derivatives and evaluate them for their anticancer and antibacterial activity.

METHODS

The synthesized compounds were characterized by IR, NMR, mass, and elemental studies. The in vitro cytotoxicity studies were performed for human breast cancer (MCF-7) and human lung cancer (A549) cells and HepG2 cell-line and compared to standard drug doxorubicin by MTT assay. Antimicrobial activity of the synthesized 2,4-thiazolidinediones derivatives was carried out using the cup plate method with slight modification.

RESULTS

The results obtained showed that TZ-5 and TZ-13 exhibited good antiproliferative activity against A549 cancer cell-line, whereas TZ-10 exhibited moderate antiproliferative activity against HepG2 cell-line when compared to standard drug doxorubicin. TZ-5 also exhibited reasonable activity against the MCF-7 cell-line with doxorubicin as standard. TZ-4, TZ-5, TZ-6, TZ-7, and TZ- 16 exhibited remarkable antibacterial activity against Gram positive and moderate activity against Gram negative bacteria with the standard drug ciprofloxacin.

CONCLUSION

Attachment of heterocyclic rings containing nitrogen as the hetero atom improves the anticancer and antimicrobial potential. Attachment of electronegative elements like halogens can also enhance the antimicrobial activity. Further structure modifications may lead to the development of more potent 2,4-TZD leads that can be evaluated for further advanced studies.

Discovery of Novel Fungal Lanosterol 14α-Demethylase (CYP51)/Histone Deacetylase Dual Inhibitors to Treat Azole-Resistant Candidiasis

Invasive fungal infections (particularly candidiasis) are emerging as severe infectious diseases worldwide. Because of serious antifungal drug resistance, therapeutic efficacy of the current treatment for candidiasis is limited and associated with high mortality. However, it is highly challenging to develop novel strategies and effective therapeutic agents to combat drug resistance. Herein, the first generation of lanosterol 14α-demethylase (CYP51)-histone deacetylase (HDAC) dual inhibitors was designed, which exhibited potent antifungal activity against azole-resistant clinical isolates. In particular, compounds 12h and 15j were highly active both in vitro and in vivo to treat azole-resistant candidiasis. Antifungal mechanism studies revealed that they acted by blocking ergosterol biosynthesis and HDAC catalytic activity in fungus, suppressing the function of efflux pump, yeast-to-hypha morphological transition, and biofilm formation. Therefore, CYP51-HDAC dual inhibitors represent a promising strategy to develop novel antifungal agents against azole-resistant candidiasis.

Antifungal drugs: New insights in research & development

The need for better antifungal therapy is commonly accepted in view of the high mortality rates associated with systemic infections, the low number of available antifungal classes, their associated toxicity and the increasing number of infections caused by strains with natural or acquired resistance. The urgency to expand the range of therapeutic options for the treatment of fungal infections has led researchers in recent decades to seek alternative antifungal targets when compared to the conventional ones currently used. Although new potential targets are reported, translating the discoveries from bench to bedside is a long process and most of these drugs fail to reach the patients. In this review, we discuss the development of antifungal drugs focusing on the approach of drug repurposing and the search for novel drugs for classical targets, the most recently described gene targets for drug development, the possibilities of immunotherapy using antibodies, cytokines, therapeutic vaccines and antimicrobial peptides.

3,5-Disubstituted Thiazolidine-2,4-Diones: Design, Microwave-Assisted Synthesis, Antifungal Activity, and ADMET Screening

A series of 12 new thiazolidine-2,4-dione derivatives were obtained by microwave-assisted synthesis. All compounds were physicochemically characterized by quantitative elemental C, H, N, S analysis and spectral data (mass spectrometry [MS], infrared [IR], and nuclear magnetic resonance [NMR]), with the results being in agreement with the expected data. An in vitro screening performed on Candida albicans ATCC 10231 showed their moderate antifungal activity, which was further investigated by determining the minimum inhibitory concentration and minimum fungicidal concentration values for the most active compounds on four strains of Candida. The molecular docking studies, performed against a fungal lanosterol 14α-demethylase, emphasized the importance of different molecular fragments in the compounds' structures for their antifungal activity. The synthesized compounds were subjected to in silico screening for the prediction of their absorption, distribution, metabolism, excretion, and toxicity (ADMET) and molecular properties. The results of the antifungal activity assays, docking study, and ADMET predictions revealed that the synthesized compounds are potential anti- Candida agents that might act by interacting with the fungal lanosterol 14α-demethylase and could be further optimized and developed as antifungal agents.

Newer patents in antimycotic therapy

There has been a global upsurge in fungal infections due to rise in immunodeficiencies, debilitation and situations of violated anatomical barriers. The available antifungal repertoire has limited activity and is fraught with toxicity concerns. Drug resistance has also shown a rapid upward trend. This has resulted in increased treatment failures, mortality and health care costs. Novel effective and safe antimycotics are needed. Analogues of existing antifungal compounds and new molecules are being developed. New targets are being explored for their putative role in curtailing fungal infections. Newer antigens as vaccine candidates are being researched into. Focused efforts in this direction have yielded encouraging results. This review illuminates the various antifungal strategies which hold promise for the future.

In Vivo Anti-Candida Activity of Phenolic Extracts and Compounds: Future Perspectives Focusing on Effective Clinical Interventions

Candida species have increasingly deserved a special attention among the medical community. In spite of the presence of Candida species as a human commensal, alarming rates of local and systemic infections have been observed, varying from moderate to severe impact. Currently available antifungal drugs have progressively lost their effectiveness, pointing urgently the problem of the microorganisms with acquired-resistance. Natural matrices are secularly used for numerous purposes, being inclusive and highly effective as antimicrobials. Increasing evidence gives a particular emphasis to the contribution of phenolic extracts and related individual compounds. In vitro studies clearly confirm their prominent effects, but the confirmation through in vivo studies, including the involved mechanisms of action, is not so much deepened. Therefore, the present report aims to provide extensive knowledge about all these aspects, highlighting the most efficient phytochemical formulations, including therapeutic doses. Further studies need to be incited to deepen knowledge on this area, namely, focused on clinical trials to provide safer and more effective antimicrobials than the current ones.

Discovery of highly potent triazoleantifungal agents with piperidine-oxadiazole side chains

A series of novel triazole antifungal agents containing piperidine-oxadiazole side chains were designed and synthesized. Compound 11b was highly active against Candida albicans with a MIC value of 0.016 μg mL⁻¹.