Chemoproteomic identification of molecular targets of antifungal prototypes, thiosemicarbazide and a camphene derivative of thiosemicarbazide, in Paracoccidioides brasiliensis

In vitro antiproliferative and apoptotic effects of thiosemicarbazones based on (-)-camphene and R-(+)-limonene in human melanoma cells

A series of 38 thiosemicarbazone derivatives based on camphene and limonene were evaluated for their antiproliferative activity. Among them, 19 were synthesized and characterized using proton and carbon-13 nuclear magnetic resonance (1H and 13C NMR). For initial compound selection, human melanoma cells (SK-MEL-37) were exposed to a single concentration of a compound (100 μM) for 24, 48, and 72 hours, and cell detachment was visually observed. Cell viability was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Nineteen compounds (4, 6, 8, 11, 13, 14, 15, 16, 17, 18, 20, 22, 25, 26, 31, 3', 4', 6', and 9') yielded cell viability below 20%. Subsequently, IC50 values for these compounds were determined, ranging from 11.56 to 55.38 μM, after 72 hours of treatment. Compound 17 (o-hydroxybenzaldehyde (-)-camphene-based thiosemicarbazone) demonstrated the lowest IC50 value, followed by compound 4 (benzaldehyde (-) camphene-based thiosemicarbazone) at 12.84 μM. Regarding compound 4, we observed the induction of a characteristic ladder pattern of DNA fragmentation through gel electrophoresis. Furthermore, fluorescence, flow cytometry and scanning microscopy assays revealed morphological changes consistent with apoptosis induction. Additionally, the measurement of caspase 6 and 8 activity in cellular extracts after treatment for 2, 4, 6, and 24 hours suggested the potential involvement of the extrinsic apoptosis pathway in the mechanism of action of compound 4. Further investigations, including molecular docking studies, are required to fully explore the potential of compound 4 and the other selected compounds, highlighting their promising role in future melanoma therapy research.

Synthesis, Antifungal Activity, Cytotoxicity and QSAR Study of Camphor Derivatives

Control of fungal phytopathogens affecting crops and woodlands is an important goal in environmental management and the maintenance of food security. This work describes the synthesis of 37 camphor derivatives, of which 27 were new compounds. Their antifungal effects on six fungi were evaluated in vitro. Compounds 3a, 4a and 5k showed strong antifungal activity against Trametes versicolor, with EC₅₀ values of 0.43, 6.80 and 4.86 mg/L, respectively, which were better than that of tricyclazole (EC₅₀ 118.20 mg/L) and close to or better than that of carbendazim (EC₅₀ 1.20 mg/L). The most potent compound, 3a, exhibited broad-spectrum antifungal activity towards six fungi with EC₅₀ values within the range of 0.43–40.18 mg/L. Scanning electron microscopy demonstrated that compounds 3a, 4a and 5k gave irregular growth and shriveling of the mycelia. In vitro cytotoxicity evaluation revealed that the tested camphor derivatives had mild or no cytotoxicity for LO₂ and HEK293T cell lines. Quantitative structure−activity relationship (QSAR) analysis revealed that the number of F atoms, relative molecular weight, the atomic orbital electronic population and total charge on the positively charged surfaces of the molecules of camphor derivatives have effects on antifungal activity. The present study may provide a theoretical basis for a high-value use of camphor and could be helpful for the development of novel potential antifungals.

Synthesis, characterization, DFT calculation, antioxidant activity, ADMET and molecular docking of thiosemicarbazide derivatives and their Cu (II) complexes

In this work, new thiosemicarbazides (ECA-1, ECA-2) and their Cu (II) complexes (ECA-1-Cu, ECA-2-Cu) were synthesized and their structures were characterized by ¹H NMR, ¹³C NMR, FT-IR, LC-MS, UV-Vis, and thermogravimetric analysis methods. Also, the surface morphology of the all compounds were examined by SEM (Scanning Electron Microscope). In the second stage, in vitro antioxidant capacity of the obtained compounds was investigated. The evaluation of the antioxidant properties of both synthesized ligands and complexes in this study was carried out by DPPH and FRAP methods. According to the results, both complexes exhibited more antioxidant capacity than the corresponding ligands. When antioxidant effects are compared for DPPH (SC₅₀ = 5.27 ± 0.05 μM) and for FRAP (7845.69 ± 16.75 mmolTE/g), compound ECA-2-Cu appears to have the best inhibition effect. The complexes were found non-electrolytic in nature with melting point of above 250 °C, and electronic spectra and magnetic behavior demonstrated that the complexes were found to be tetrahedral geometry. Further, in silico the ADMET properties which studies are a significant role in improving and predicting drug compounds were calculated using web-based platforms. The theoretical calculations were made using the method of Density Functional Theory (Frontier molecular orbital analyze and Nonlinear optical properties). Also, molecular docking studies were performed to evaluate the binding interactions between the ligand and complex compounds and Human Peroxiredoxin 2. Both in vitro and in silico results indicated that synthesized compounds could act as potent antioxidant agents.

One Century of Study: What We Learned about Paracoccidioides and How This Pathogen Contributed to Advances in Antifungal Therapy

Paracoccidioidomycosis (PCM) is a notable fungal infection restricted to Latin America. Since the first description of the disease by Lutz up to the present day, Brazilian researchers have contributed to the understanding of the life cycle of this pathogen and provided the possibility of new targets for antifungal therapy based on the structural and functional genomics of Paracoccidioides. In this context, in silico approaches have selected molecules that act on specific targets, such as the thioredoxin system, with promising antifungal activity against Paracoccidioides. Some of these are already in advanced development stages. In addition, the application of nanostructured systems has addressed issues related to the high toxicity of conventional PCM therapy. Thus, the contribution of molecular biology and biotechnology to the advances achieved is unquestionable. However, it is still necessary to transcend the boundaries of synthetic chemistry, pharmaco-technics, and pharmacodynamics, aiming to turn promising molecules into newly available drugs for the treatment of fungal diseases.

Beyond Melanin: Proteomics Reveals Virulence-Related Proteins in Paracoccidioides brasiliensis and Paracoccidioides lutzii Yeast Cells Grown in the Presence of L-Dihydroxyphenylalanine

Species of the genus Paracoccidioides cause a systemic infection in human patients. Yeast cells of Paracoccidioides spp. produce melanin in the presence of L-dihydroxyphenylalanine and during infection, which may impact the pathogen’s survival in the host. To better understand the metabolic changes that occur in melanized Paracoccidioides spp. cells, a proteomic approach was performed to compare melanized and non-melanized Paracoccidioides brasiliensis and Paracoccidioides lutzii yeast cells. Melanization was induced using L-dihydroxyphenylalanine as a precursor, and quantitative proteomics were performed using reversed-phase nano-chromatography coupled to high-resolution mass spectrometry. When comparing melanized versus non-melanized cells, 1006 and 582 differentially abundant/detected proteins were identified for P. brasiliensis and P. lutzii, respectively. Functional enrichment and comparative analysis revealed 30 important KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways in melanized P. brasiliensis and 18 in P. lutzii, while differentially abundant proteins from non-melanized cells from these species were involved in 21 and 25 enriched pathways, respectively. Melanized cells presented an abundance of additional virulence-associated proteins, such as phospholipase, proteases, superoxide dis-mutases, heat-shock proteins, adhesins, and proteins related to vesicular transport. The results suggest that L-dihydroxyphenylalanine increases the virulence of Paracoccidioides spp. through complex mechanisms involving not only melanin but other virulence factors as well.

(-)-Camphene-based derivatives as potential antibacterial agents against Staphylococcus aureus and Enterococcus spp

Aim: To evaluate the activity of (-)-camphene-based thiosemicarbazide (TSC) and 4-hydroxy-thiosemicarbazone (4-OH-TSZ), alone and in combination against Gram-positive. Material & methods: MIC were determined for Staphylococcus aureus, Enterococcus spp. reference strains and clinical isolates. Drug combination, time-kill and cytotoxicity assays were also performed. Results: TSC and 4-OH-TSZ demonstrated potent inhibitory activity against S. aureus and Enterococcus spp., including multidrug-resistant isolates (MIC ranging from 1.9 to 31.2 μg/ml), and were bactericidal for the reference strains of both Gram-positive tested. The derivatives proved to be selective for the bacteria and synergistic with oxacillin and vancomycin. Conclusion: (-)-Camphene-based derivatives can represent promising drug candidates against critical pathogens, such as S. aureus and Enterococcus spp., including MRSA and vancomycin resistance Enterococcus spp. isolates.

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

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

Silva L, Gonçales RA, Neves BJ, Soares CM, Pereira M. Setting New Routes for Antifungal Drug Discovery Against Pathogenic Fungi

:

Fungal diseases are life-threatening to human health and responsible for millions of deaths around the world. Fungal pathogens lead to a high number of morbidity and mortality. Current antifungal treatment comprises drugs, such as azoles, echinocandins, and polyenes and the cure is not guaranteed. In addition, such drugs are related to severe side effects and the treatment lasts for an extended period. Thus, setting new routes for the discovery of effective and safe antifungal drugs should be a priority within the health care system. The discovery of alternative and efficient antifungal drugs showing fewer side effects is time-consuming and remains a challenge. Natural products can be a source of antifungals and used in combinatorial therapy. The most important natural products are antifungal peptides, antifungal lectins, antifungal plants, and fungi secondary metabolites. Several proteins, enzymes, and metabolic pathways could be targets for the discovery of efficient inhibitor compounds and recently, heat shock proteins, calcineurin, salinomycin, the trehalose biosynthetic pathway, and the glyoxylate cycle have been investigated in several fungal species. HSP protein inhibitors and echinocandins have been shown to have a fungicidal effect against azole-resistant fungi strains. Transcriptomic and proteomic approaches have advanced antifungal drug discovery and pointed to new important specific-pathogen targets. Certain enzymes, such as those from the glyoxylate cycle, have been a target of antifungal compounds in several fungi species. Natural and synthetic compounds inhibited the activity of such enzymes and reduced the ability of fungal cells to transit from mycelium to yeast, proving to be promisor antifungal agents. Finally, computational biology has developed effective approaches, setting new routes for early antifungal drug discovery since normal approaches take several years from discovery to clinical use. Thus, the development of new antifungal strategies might reduce the therapeutic time and increase the quality of life of patients.

Mass Spectrometry-Based Proteomics of Fungal Pathogenesis, Host-Fungal Interactions, and Antifungal Development

The prevalence of fungal diseases is increasing on a global scale, ranging from acute to systemic infections caused by commensal or pathogenic microorganisms, often associated with the immune status of the host. Morbidity and mortality rates remain high and our ability to treat fungal infections is challenged by a limited arsenal of antifungal agents and the emergence of drug resistant pathogens. There is a high demand for new approaches to elucidate the fungal mechanisms of pathogenesis and the interplay between host and pathogen to discover novel treatment options. Moreover, the need for improved drug efficacy and reduced host toxicity requires the identification and characterization of antifungal biological targets and molecular mechanisms of action. Mass spectrometry (MS)-based proteomics is a rapidly advancing field capable of addressing these priorities by providing comprehensive information on the dynamics of cellular processes, modifications, and interactions. In this Review, we focus on applications of MS-based proteomics in a diverse array of fungal pathogens and host systems to define and distinguish the molecular details of fungal pathogenesis and host–fungal interactions. We also explore the emerging role of MS-based proteomics in the discovery and development of novel antifungal therapies and provide insight into the future of MS-based proteomics in fungal biology.