Design, Synthesis, and Antifungal/Anti-Oomycete Activities of Novel 1,2,4-Triazole Derivatives Containing Carboxamide Fragments

Plant diseases caused by pathogenic fungi or oomycetes seriously affect crop growth and the quality and yield of products. A series of novel 1,2,4-triazole derivatives containing carboxamide fragments based on amide fragments widely used in fungicides and the commercialized mefentrifluconazole were designed and synthesized. Their antifungal activities were evaluated against seven kinds of phytopathogenic fungi/oomycete. Results showed that most compounds had similar or better antifungal activities compared to mefentrifluconazole's inhibitory activity against Physalospora piricola, especially compound 6h (92%), which possessed outstanding activity. Compound 6h (EC50 = 13.095 μg/mL) showed a better effect than that of mefentrifluconazole (EC50 = 39.516 μg/mL). Compound 5j (90%) displayed outstanding anti-oomycete activity against Phytophthora capsici, with an EC50 value of 17.362 μg/mL, far superior to that of mefentrifluconazole (EC50 = 75.433 μg/mL). The result of molecular docking showed that compounds 5j and 6h possessed a stronger affinity for 14α-demethylase (CYP51). This study provides a new approach to expanding the fungicidal spectrum of 1,2,4-triazole derivatives.

Sporothrix brasiliensis: Epidemiology, Therapy, and Recent Developments

Sporotrichosis caused by Sporothrix brasiliensis is an emergent mycosis that is now a worldwide concern. One important step to sporotrichosis control is its correct treatment. However, limitations abound; thus, new antifungals, mainly focused on S. brasiliensis, are urgently needed. We performed a systematic review (following the PRISMA guideline) focused on (1) the global distribution of human and animal sporotrichosis by S. brasiliensis, especially outside of Brazil; (2) appraising therapies tested against this pathogen. We identified sporotrichosis caused by S. brasiliensis reported in five countries (Paraguay, Chile, Argentina, the United Kingdom, and the United States) in addition to Brazil, occurring on three continents, highlighting the epidemiological scenario in Argentina with an important increase in reported cases in recent years. Regarding the antifungal activity of drugs, 25 articles described the in vitro action of 20 unique chemicals and eight repurposed drugs against S. brasiliensis. Only five studies reported in vivo activity against S. brasiliensis (five drugs) using invertebrate and vertebrate models. Sporotrichosis caused by S. brasiliensis has a global impact and it is no longer specifically a Brazilian problem. We review the need for understanding the disease epidemiology, education of clinicians and of the populace, organization of health care delivery to respond to a spreading epidemic, and research on therapy for sporotrichosis.

Design, Synthesis, and Evaluation of Antifungal Bioactivity of Novel Pyrazole Carboxamide Thiazole Derivatives as SDH Inhibitors

Agricultural production is seriously threatened by plant pathogens. The development of new fungicides with high efficacy and low toxicity is urgently needed. In this study, a series of pyrazole carboxamide thiazole derivatives were designed, synthesized, and evaluated for their antifungal activities against nine plant pathogens in vitro. Bioassay results showed that most compounds (3i, 5i, 6i, 7i, 9i, 12i, 16i, 19i, and 23i) exhibited good antifungal activities against Valsa mali. In particular, compounds 6i and 19i exhibited better antifungal activities against Valsa mali with EC₅₀ values of 1.77 and 1.97 mg/L, respectively, than the control drug boscalid (EC₅₀ = 9.19 mg/L). Additionally, compound 23i exhibited excellent inhibitory activity against Rhizoctonia solani, with an EC₅₀ value of 3.79 mg/L. Compound 6i at 40 mg/L showed a satisfactory in vivo protective effect against Valsa mali. Scanning electron microscopy analyses revealed that compound 6i could significantly damage the surface morphology to interfere with the growth of Valsa mali. In molecular docking, the results showed that compound 6i interacts with TRP O: 173, SER P: 39, TYR Q: 58, and ARG P: 43 of succinate dehydrogenase (SDH) through hydrogen bonding and σ-π interaction, and its binding mode is similar to that of boscalid and SDH. The enzyme activity experiment also further verified its action mode. Our studies suggested that pyrazole carboxamide thiazole derivative 6i provided a valuable reference for the further development of succinate dehydrogenase inhibitors.

Effectiveness of diphenyl diselenide against experimental sporotrichosis caused by Sporothrix brasiliensis

Diphenyl diselenide (PhSe)2 is a stable organoselenium compound with promising in vitro antifungal activity against several fungi, including Sporothrix brasiliensis. This species is associated with feline and zoonotic sporotrichosis, an emergent mycosis in Latin America. We evaluated the activity of (PhSe)2, alone and in association with itraconazole, in the treatment of sporotrichosis caused by S. brasiliensis, in a murine model. Sixty mice were subcutaneously infected with S. brasiliensis in the footpad and treated by gavage for 30 consecutive days. The six treatment groups received: no active treatment, itraconazole (50 mg/kg), (PhSe)2 at 1, 5, and 10 mg/kg dosages, or itraconazole (50 mg/kg) + (PhSe)2 1 mg/kg, once a day, starting seven days post-inoculation. A significant reduction in the fungal burden of internal organs was achieved in the groups treated with (PhSe)2 1 mg/kg or itraconazole alone in comparison with the untreated group. Higher dosages (5 and 10 mg/kg) of (PhSe)2 increased the clinical manifestation of sporotrichosis and mortality rate. Treatment with both itraconazole and (PhSe)2 1 mg/kg was better than their activities alone (P < .001). This is the first demonstration of the potential use of (PhSe)2, alone or with the present drug of choice, in the treatment of sporotrichosis.

Initial Results of the International Efforts in Screening New Agents against Candida auris

BACKGROUND

Candida auris is an emergent fungal pathogen and a global concern, mostly due to its resistance to many currently available antifungal drugs.

OBJECTIVE

Thus, in response to this challenge, we evaluated the in vitro activity of potential new drugs, diphenyl diselenide (PhSe)₂ and nikkomycin Z (nikZ), alone and in association with currently available antifungals (azoles, echinocandins, and polyenes) against Candida auris.

METHODS

Clinical isolates of C. auris were tested in vitro. (PhSe)₂ and nikZ activities were tested alone and in combination with amphotericin B, fluconazole, or the echinocandins, micafungin and caspofungin.

RESULTS

(PhSe)₂ alone was unable to inhibit C. auris, and antagonism or indifferent effects were observed in the combination of this compound with the antifungals tested. NikZ appeared not active alone either, but frequently acted cooperatively with conventional antifungals.

CONCLUSION

Our data show that (PhSe)₂ appears to not have a good potential to be a candidate in the development of new drugs to treat C. auris, but that nikZ is worthy of further study.

In Vitro Activity of Ebselen and Diphenyl Diselenide Alone and in Combination with Drugs against Trichophyton mentagrophytes Strains

Background: Dermatophytoses are one of the most prevalent infectious diseases in the world for which the pace of developing new drugs has not kept pace with the observed therapeutic problems. Thus, searching for new antifungals with an alternative and novel mechanism of action is necessary. Objective: This study aimed to evaluate the antifungal activity of ebselen and diphenyl diselenide against Trichophyton mentagrophytes clinical isolates. Methods: In vitro antifungal susceptibility was assessed for organoselenium compounds used alone or in combination with allylamines and azoles according to the 3rd edition of the CLSI M38 protocol. Results: Ebselen demonstrated high antifungal activity with MIC_GM equal to 0.442 μg/mL and 0.518 μg/mL in the case of human and animal origin strains, respectively. The values of MIC_GM of diphenyl diselenide were higher: 17.36 μg/mL and 13.45 μg/mL for the human and animal isolates, respectively. Synergistic or additive effects between terbinafine and ebselen or diphenyl diselenide were observed in the case of 12% and 20% strains, respectively. In turn, the combination of itraconazole with diphenyl diselenide showed a synergistic effect only in the case of 6% of the tested strains, whereas no synergism was shown in the combination with ebselen. Conclusions: The results highlight the promising activity of organoselenium compounds against Trichophyton mentagrophytes. However, their use in combinational therapy with antifungal drugs seems to be unjustified due to the weak synergistic effect observed.

Mucoadhesive gellan gum hydrogel containing diphenyl diselenide-loaded nanocapsules presents improved anti-candida action in a mouse model of vulvovaginal candidiasis

The aim of this study was to evaluate the in vitro antifungal action of a diphenyl diselenide-loaded poly(ε-caprolactone) nanocapsules suspension (NC-1) and incorporate it into a gellan gum hydrogel formulation in order to assess its in vivo efficacy in an animal model of vulvovaginal candidiasis. Nanocapsules suspensions containing the compound (NC-1 ∼ 5 mg/mL) or not (NC-B) were prepared by the interfacial deposition of preformed polymer method. To estimate in vitro antifungal effect, the broth microdilution test was applied. The results showed that NC-1 had equal or lower MIC values when compared to free compound against fifteen Candida strains. Following, the hydrogel was prepared by direct thickening of the nanocapsules suspension by gellan gum addition. The animal model of vulvovaginal candidiasis was induced by infecting female Swiss mice with Candida albicans strains. The animals were topically treated with 20 µL of hydrogels (NC-1 and free compound - 0.1 mg of diphenyl diselenide/once a day for seven days) and then the total fungal burden was assessed after the euthanasia. The results showed that the hydrogels presented pH in the acidic range, compound content close to theoretical value, homogeneous particle distribution with nanometric size, high physicochemical and microbiological stability as well as great bioadhesive property. The nano-based presented superior pharmacological action in comparison to the hydrogel containing non-encapsulated diphenyl diselenide. The results demonstrated that the nanoencapsulation maintained the effective antifungal action of diphenyl diselenide. The nano-based hydrogel formulation may be considered a promising approach against vulvovaginal candidiasis.

CATastrophe: response to the challenges of zoonotic sporotrichosis in southern Brazil

BACKGROUND

In Brazil, zoonotic sporotrichosis became a national public health problem, with thousands of cases in the last decade in several regions of the country. In this context, health education activities are critical, especially in promoting early diagnosis and access to proper health care in sporotrichosis hyperendemic areas. Therefore, we report the implementation of a public specialized reference service (SRS) for diagnosis and treatment of sporotrichosis in southern Brazil We evaluated the impact of the SRS on diagnostic confirmation and speed of diagnosis.

METHODS

The SRS was implemented in Rio Grande city. We implemented a public service to promote the correct diagnosis, treatment and follow-up of human sporotrichosis cases. To study the impact of implementing SRS, the annual number of cases, and the period between the appearance of lesions until diagnosis were compared, using prior data and that post-implementation.

RESULTS

The implementation of the SRS directly benefited almost 50 patients in only four years, with the collaboration of almost 50% of the local health groups, together with an increase of more than 200% in diagnosis confirmation and speed of diagnosis, showing the reach, impact and importance of the SRS.

CONCLUSION

The impact on the individual and collective health of the local population highlights the value of this public health approach in facing the epidemiological threat of zoonotic sporotrichosis.

Synergism of Nikkomycin Z in Combination with Diphenyl Diselenide Against Sporothrix spp

We evaluated the in vitro activity of nikkomycin Z (NikZ) in combination with diphenyl diselenide (PhSe)₂, two compounds previously shown to have anti-Sporothrix spp. activity. Eighteen isolates of Sporothrix spp. were tested in checkerboard assays. Synergism for inhibition and killing Sporothrix spp. occurred in 100% and 89% of the isolates, respectively. The anti-Sporothrix spp. activity of this combination provides a rationale for in vivo studies to evaluate the application of both compounds in sporotrichosis treatment.

Diphenyl diselenide alone and in combination with itraconazole against Sporothrix schenckii s.str. and Sporothrix globosa

We evaluated the in vitro susceptibility of Sporothrix schenckii s.str. and Sporothrix globosa to diphenyl diselenide (PhSe)₂ alone and in association with itraconazole (ITZ). Eight clinical isolates were tested in microdilution and checkerboard assays. (PhSe)₂ alone inhibited all isolates in concentration ≤ 8 µg/mL and was effective in killing one S. schenckii isolate. Inhibitory and fungicidal beneficial effects in its interaction with ITZ were shown against 87.5% (7/8) and 50% (4/8) of the isolates tested, respectively. Our study demonstrates the in vitro antifungal activity of (PhSe)₂ against two pathogenic Sporothrix species, suggesting studies of in vivo applications are warranted.

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Sporothrix Brasiliensis: A Review of an Emerging South American Fungal Pathogen, Its Related Disease, Presentation and Spread in Argentina

Sporotrichosis, caused by Sporothrix schenckii and related species, is the most frequent implantation mycosis in Latin America. In Argentina, over the last 8 years, there have been 0.16 new cases per month of feline sporotrichosis in 2011, increasing to 0.75 cases per month in 2019 and involving zoonotic transmission to humans. Molecular identification by polymerase chain reaction (PCR) detected Sporothrix brasiliensis in these feline and zoonotic outbreaks. This study will focus on different feline and human sporotrichosis outbreaks caused by S. brasiliensis in Argentina during 2011–2019. We will address the sources of infection and environmental hotspots, as well as the application of several treatment strategies for improving the pharmacotherapy of the different clinical forms of the disease. Finally, we will provide a detailed summary of the clinical aspects and new advances in host–pathogen interactions, virulence factors and immune response, focusing on state-of-the-art diagnostic tools and potential vaccine candidates.

(PhSe)2 and (pCl-PhSe)2 organochalcogen compounds inhibit Candida albicans adhesion to human endocervical (HeLa) cells and show anti-biofilm activities

Adhesion capacity on biological surfaces and biofilm formation is considered an important step in the infection process by Candida albicans. The ability of (PhSe)₂ and (pCl-PhSe)₂, two synthetic organic selenium (organochalcogen) compounds, to act on C. albicans virulence factors related to adhesion to human endocervical (HeLa) cell surfaces and their anti-biofilm activities was analyzed. Both organochalcogen compounds inhibited C. albicans adhesion to HeLa cells, dependent on compound concentrations. (PhSe)₂ (at 20 µM; p = 0.0012) was significantly more effective than (pCl-PhSe)₂ (at 20 µM; p = 0.0183) compared with the control. (PhSe)₂ inhibited biofilm formation and decreased biofilm viability in both early and mature biofilms more efficiently than (pCl-PhSe)₂. Overall, the organochalcogen compounds, especially (PhSe)₂, were demonstrated to be effective antifungal drugs against C. albicans virulence factors related to epithelial cell surface adhesion and the formation and viability of biofilms.

Ebselen and diphenyl diselenide against fungal pathogens: A systematic review

Fungal infections are one of the most prevalent diseases in the world and there is a lack of new antifungal drug development for these diseases. We conducted a systematic review of the literature regarding the in vitro antifungal activity of the organoselenium compounds ebselen (Eb) and diphenyl diselenide [(PhSe)2]. A systematic review was carried out based on the search for articles with data concerning Minimal Inhibitory Concentration (MIC) values, indexed in international databases and published until August 2020. A total of 2337 articles were found, and, according to the inclusion and exclusion criteria used, 22 articles were included in the study. Inhibitory activity against 96% (200/208) and 95% (312/328) of the pathogenic fungi tested was described for Eb and [(PhSe)2], respectively. Including in these 536 fungal isolates tested, organoselenium activity was highlighted against Candida spp., Cryptococcus ssp., Trichosporon spp., Aspergillus spp., Fusarium spp., Pythium spp., and Sporothrix spp., with MIC values lower than 64 μg/mL. In conclusion, Eb and [(PhSe)2] have a broad spectrum of in vitro inhibitory antifungal activity. These data added with other pharmacological properties of these organoselenium compounds suggest that both compounds are potential future antifungal drugs. Whether MICs toward the upper end of the ranges described here are compatible with efficacious therapy, and whether they may achieve such end as a result of the favorable non-antimicrobial effects of selenium on the host, requires more in vivo testing.

Diphenyl diselenide and its interaction with antifungals against Aspergillus spp

Given the few antifungal classes available to treat aspergillosis, this study aimed to evaluate the in vitro antifungal activity of diphenyl diselenide (PhSe)2 alone and in combination with classical antifungals against Aspergillus spp., and its in vivo activity in a systemic experimental aspergillosis model. We performed in vitro broth microdilution assay of (PhSe)2 against 32 Aspergillus isolates; and a checkboard assay to test the interaction of this compound with itraconazole (ITC), voriconazole (VRC), amphotericin B (AMB), and caspofungin (CAS), against nine Aspergillus isolates. An experimental model of invasive aspergillosis in mice was studied, and survival curves were compared between an untreated group and groups treated with 100 mg/kg ITC, or (PhSe)2 in different dosages (10 mg/kg, 50 mg/kg and 100 mg/kg). All Aspergillus non-fumigatus and 50% of A. fumigatus were inhibited by (PhSe)2 in concentrations ≤ 64 µg/ml, with significant differences in MICs between the sections. Synergism or additive effect in the in vitro (PhSe)2 interaction with VRC and CAS was observed against the majority of isolates, and with ITC against the non-fumigatus strains. In addition to the inhibitory interaction, (PhSe)2 was able to add a fungicidal effect to CAS. Survival curves from the systemic experimental aspergillosis model demonstrated that the inoculum caused an acute and lethal infection in mice, and no treatment applied significantly prolonged survival over that of the control group. The results highlight the promising activity of (PhSe)2 against Aspergillus species, but more in vivo studies are needed to determine its potential applicability in aspergillosis treatment.

LAY SUMMARY

The activity of diphenyl diselenide (PhSe)2 alone and in combination with itraconazole, voriconazole, and caspofungin, is described against three of the most pathogenic Aspergillus sections. (PhSe)2 may prove useful in therapy of infection in future; further study is required.

Potential use of Nikkomycin Z as an anti- Sporothrix spp. drug

Sporotrichosis, the most common subcutaneous mycosis in several countries, is caused by the dimorphic fungus, Sporothrix spp. Given some limitations in the treatment of this disease, and the high potential of nikkomycin Z (NikZ) as an antifungal against dimorphic fungi, this study aimed to evaluate the in vitro susceptibility of Sporothrix spp. to NikZ alone and with the drug of choice, itraconazole (ITZ). Seventeen clinical isolates of three Sporothrix spp. species (10 S. brasiliensis, six S. schenckii sensu stricto and one S. globosa) were tested in microdilution and checkerboard assays. Minimal inhibitory concentration (MIC), minimal fungicidal concentration (MFC), fractional inhibitory and fungicidal concentration indexes (FICi and FFCi) were analyzed. MIC of NikZ alone could be determined against S. globosa (12.5 μg/ml) and against 67% (4/6) and 30% (3/10) of the S. schenckii sensu stricto and S. brasiliensis isolates, respectively (≤ 400 μg/ml). Synergism with ITZ was showed against almost all the isolates tested (94%; 16/17), including reversing resistance to ITZ alone in some isolates. Our study shows the potential of NikZ in sporotrichosis treatment. Further studies in experimental models are needed to understand the possible future application of this drug as an alternative therapy or as an adjuvant in sporotrichosis treatment.

LAY ABSTRACT

Sporotrichosis is a subcutaneous and lymphatic infection, caused by fungi of Sporothrix spp. Our study shows the potential of NikZ to inhibiting Sporothrix species in vitro. Further studies are needed to understand the future application of this drug to sporotrichosis treatment.

Immunity and Treatment of Sporotrichosis

Species of the Sporothrix complex are the etiological agents of sporotrichosis, an important subcutaneous mycosis with several clinical forms and an increasing incidence around the world that affects humans and other mammals. The immunological mechanisms involved in the prevention and control of this mycosis are not entirely understood. Many reports have suggested that cell-mediated immunity has an essential role in the development of the disease, being the primary response controlling it, while only recent data supports that the humoral response is essential for the appropriate control. This mycosis is a challenge for diagnosis since the culture and isolation of the organism are time-consuming and complicated; reasons that have led to the study of fungus antigenic molecules capable of generating a detectable humoral response. The treatment for this disease includes the use of several antifungal drugs like itraconazole, amphotericin B, caspofungin, fluconazole, and the combination between them among others such as the extract of Vismia guianensis.