In vitro evaluation of the efficacy of 8-hydroxyquinoline derivatives for the control of Phaeomoniella chlamydospora, the causative agent of Petri disease in grapevines.

AIM: This study evaluates the in vitro efficacy of 8-hydroxyquinoline (8HQ) derivatives in controlling the phytopathogenic fungus Phaeomoniella chlamydospora. METHODS AND RESULTS: The in vitro tests assessed the susceptibility to the minimum inhibitory concentration (MIC), checkerboard assay, mycelial growth (MG) inhibition, and EC50 determination. Among the seven agricultural fungicides tested, tebuconazole (TEB) displayed the lowest MIC, 1.01 µg mL-1, followed by captan (CAP), thiophanate methyl (TM), and mancozeb with MICs of 4.06, 5.46, and 10.62 µg mL-1, respectively. The 8HQ derivatives used in this study were clioquinol and PH 151 (PH) with MICs of 1.09 and 2.02 µg mL-1, respectively. PH associated with TEB and CAP showed synergism and inhibited 95.8% of MG at the highest dose. TEB inhibited 100% of MG at the three highest doses, while associated with PH exhibited the lowest EC50 (0.863 + 0.0381 µg mL-1). CONCLUSIONS: We concluded that the 8HQ derivatives tested controlled effectively the P. chlamydospora in vitro. PH associated with CAP and TEB exhibited a synergistic effect. The association between PH and TM was considered indifferent. IMPACT STATEMENT: This study expands the list of active ingredients tested against P. chlamydospora, with the PH 151 and clioquinol derivatives being tested for the first time. The in vitro efficacy and synergistic action with other fungicides suggest a potential use as a grapevine wound protectant. This association makes it possible to reduce doses and increase the potency of both drugs, reducing the risk of resistance development and harm to humans and the environment.

Targeting Akt/PKB in pediatric tumors: A review from preclinical to clinical trials.

The serine/threonine kinase Akt is a major player in the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway, and its modulation impacts multiple cellular processes such as growth, proliferation, and survival. Several abnormalities in this pathway have been documented over the years, and these alterations were shown to have great implications in tumorigenesis and resistance to chemotherapy. Thus, multiple Akt inhibitors have been developed and tested in adult tumors, and some of them are currently undergoing phase I, II, and III clinical trials for distinct cancers that arise during adulthood. Despite that, the impact of these inhibitors is still not fully understood in pediatric tumors, and Akt-specific targeting seems to be a promising approach to treat children affected by cancers. This review summarizes recent available evidence of Akt inhibitors in pediatric cancers, from both preclinical and clinical studies. In short, we demonstrate the impact that Akt inhibition provides in tumorigenesis, and we suggest targeting the PI3K/Akt/mTOR signaling pathway, alone or in combination with other inhibitors, is a feasible tool to achieve better outcomes in pediatric tumors.

Clioquinol and 8-hydroxyquinoline-5-sulfonamide derivatives damage the cell wall of Pythium insidiosum.

AIMS: To evaluate the antimicrobial activity and to determine the pharmacodynamic characteristics of three 8-hydroxyquinoline derivatives (8-HQs) against Pythium insidiosum, the causative agent of pythiosis. METHODS AND RESULTS: Antimicrobial activity was tested by broth microdilution and MTT assays. The antimicrobial mode of action was investigated using sorbitol protection assay, ergosterol binding assay, and scanning electron microscopy. Clioquinol, PH151, and PH153 were active against all isolates, with MIC values ranging from 0.25 to 2 µg ml-1. They also showed a time- and dose-dependent antimicrobial effect, damaging the P. insidiosum cell wall. CONCLUSIONS: Together, these results reinforce the potential of 8-HQs for developing new drugs to treat pythiosis.

Evaluation of activity and toxicity of combining clioquinol with ciclopirox and terbinafine in alternative models of dermatophytosis.

Dermatophytosis is a superficial fungal infection that affects humans and is very common in small animals. The treatment using the most commonly used antifungals is failing, and new therapeutic alternatives are required to combat the resistance of these fungal infections. Previous studies by the group have shown that clioquinol is an important therapeutic alternative in the treatment of dermatophytosis. The object was to conduct studies of antidermatophytic activity and the irritant potential from the double and triple combinations of clioquinol, terbinafine and ciclopirox in ex vivo and in vivo alternative models. To evaluate the irritant potential of antifungal combinations, the alternative HET-CAM method (chicken egg test chorioallantoic membrane) was used. Ex vivo models were used to assess the effectiveness of antifungal combinations, using pig hooves and veterinary fur. Any possible tissue damage was to assess through in histopathology of swine ears. HET-CAM results showed that all combinations can be classified as non-irritating, corroborated by the results of the histopathological evaluation of the pig's ear skin. Only the double combinations managed to remove 100% of the colony-forming units (CFU) formed on the pig's hooves. The clioquinol + terbinafine combination and the triple combination were more effective than clioquinol + ciclopirox in eradicating the preformed biofilm in fur of veterinary origin. These results show the potential of formulations of clioquinol in combination with antifungals for use in humans and in the veterinary field to combat dermatophytosis, as an important alternative therapy, for use in the near future.

In vitro antidermatophytic synergism of double and triple combination of clioquinol with ciclopirox and terbinafine.

BACKGROUND: Dermatophytoses are the most frequent fungal infections worldwide and there have been described clinical resistance to the commonly used antifungals. Clioquinol is an antimicrobial that had the oral formulations withdrawn from the market in the 70s due to the report of neurotoxicity and recently has been considered as an effective alternative for the treatment of dermatophytosis. OBJECTIVES: To evaluate the effect of the double and triple association between clioquinol with terbinafine and ciclopirox on clinical isolates of dermatophytes. The cytotoxicity of these associations on human leukocytes was also verified. METHODS: Checkerboard method was used to evaluate the interaction between antifungal agents. Time-kill assay was used to verify fungicidal action and evaluate the combination with greater effect for TRU47 isolate. Cell viability was assessed by loss of integrity of the leukocyte membrane in order to verify the toxicity. RESULTS: Synergistic interaction was observed in 42% of isolates when terbinafine was associated with clioquinol and in 50% of isolates when ciclopirox was associated with clioquinol. The triple association resulted in synergistic interaction for 75% of the isolates. Clioquinol + terbinafine and triple combination were more effective for TRU47 isolate, and the combinations exhibited a time-dependent fungicidal effect. Furthermore, the results of cell viability demonstrated that clioquinol and terbinafine combination is not cytotoxic to human leukocytes. CONCLUSIONS: Clioquinol in combination with antifungals in the treatment of dermatophytosis can be a therapeutic strategy to overcome problems related to resistance, action spectrum and toxicity of the antifungal drugs used in the clinic.

Production of the Cytotoxic Cardenolide Glucoevatromonoside by Semisynthesis and Biotransformation of Evatromonoside by a Digitalis lanata Cell Culture.

Recent studies demonstrate that cardiac glycosides, known to inhibit Na+/K+-ATPase in humans, have increased susceptibility to cancer cells that can be used in tumor therapy. One of the most promising candidates identified so far is glucoevatromonoside, which can be isolated from the endangered species Digitalis mariana ssp. heywoodii. Due to its complex structure, glucoevatromonoside cannot be obtained economically by total chemical synthesis. Here we describe two methods for glucoevatromonoside production, both using evatromonoside obtained by chemical degradation of digitoxin as the precursor. 1) Catalyst-controlled, regioselective glycosylation of evatromonoside to glucoevatromonoside using 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide as the sugar donor and 2-aminoethyldiphenylborinate as the catalyst resulted in an overall 30 % yield. 2) Biotransformation of evatromonoside using Digitalis lanata plant cell suspension cultures was less efficient and resulted only in overall 18 % pure product. Structural proof of products has been provided by extensive NMR data. Glucoevatromonoside and its non-natural 1-3 linked isomer neo-glucoevatromonoside obtained by semisynthesis were evaluated against renal cell carcinoma and prostate cancer cell lines.

Antifungal activity of azoles, allylamines, and 8-hidroxiquinolines, alone and in combination, against Malassezia pachydermatis in vitro and in vivo.

Malassezia pachydermatis is often reported as the causative agent of dermatitis in dogs. This study aims to evaluate the in vitro and in vivo antifungal activity of azoles and terbinafine (TRB), alone and in combination with the 8-hydroxyquinoline derivatives (8-HQs) clioquinol (CQL), 8-hydroxyquinoline-5-(n-4-chlorophenyl)sulfonamide (PH151), and 8-hydroxyquinoline-5-(n-4-methoxyphenyl)sulfonamide (PH153), against 16 M. pachydermatis isolates. Susceptibility to the drugs was evaluated by in vitro broth microdilution and time-kill assays. The Toll-deficient Drosophila melanogaster fly model was used to assess the efficacy of drugs in vivo. In vitro tests showed that ketoconazole (KTZ) was the most active drug, followed by TRB and CQL. The combinations itraconazole (ITZ)+CQL and ITZ+PH151 resulted in the highest percentages of synergism and none of the combinations resulted in antagonism. TRB showed the highest survival rates after seven days of treatment of the flies, followed by CQL and ITZ, whereas the evaluation of fungal burden of dead flies showed a greater fungicidal effect of azoles when compared to the other drugs. Here we showed for the first time that CQL is effective against M. pachydermatis and potentially interesting for the treatment of malasseziosis.

Structure-based discovery of thiosemicarbazones as SARS-CoV-2 main protease inhibitors.

Aim: Discovery of novel SARS-CoV-2 main protease (Mpro) inhibitors using a structure-based drug discovery strategy. Materials & methods: Virtual screening employing covalent and noncovalent docking was performed to discover Mpro inhibitors, which were subsequently evaluated in biochemical and cellular assays. Results: 91 virtual hits were selected for biochemical assays, and four were confirmed as reversible inhibitors of SARS CoV-2 Mpro with IC50 values of 0.4-3 µM. They were also shown to inhibit SARS-CoV-1 Mpro and human cathepsin L. Molecular dynamics simulations indicated the stability of the Mpro inhibitor complexes and the interaction of ligands at the subsites. Conclusion: This approach led to the discovery of novel thiosemicarbazones as potent SARS-CoV-2 Mpro inhibitors.

Antibacterial and synergistic activity of a new 8-hydroxyquinoline derivative against methicillin-resistant Staphylococcus aureus.

Aim: To evaluate the antibacterial and synergistic effect of a new 8-hydroxyquinoline derivative (PH176) against MRSA. Materials & methods: PH176 activity was determined by broth microdilution against 38 Staphylococcus aureus clinical isolates. The antibacterial and synergistic effects with oxacillin and nitroxoline were evaluated by time-kill assays to five MRSA isolates. Toxicity was evaluated by in vitro and ex vivo models. Results: The MIC50 and MIC90 of PH176 were 16 and 32 µg/ml, respectively. The PH176 and nitroxoline led to a reduction in colony count for four isolates and the combination of PH176 and oxacillin acted synergically for three isolates. Furthermore, PH176 was determined to be noncytotoxic/nonirritant. Conclusion: These results demonstrate that PH176 has revealed promising results to be a potential candidate to treat MRSA infections.

Structure-Based Optimization of Quinazolines as Cruzain and TbrCATL Inhibitors.

The cysteine proteases, cruzain and TbrCATL (rhodesain), are therapeutic targets for Chagas disease and Human African Trypanosomiasis, respectively. Among the known inhibitors for these proteases, we have described N4-benzyl-N2-phenylquinazoline-2,4-diamine (compound 7 in the original publication, 1a in this study), as a competitive cruzain inhibitor (Ki = 1.4 µM). Here, we describe the synthesis and biological evaluation of 22 analogs of 1a, containing modifications in the quinazoline core, and in the substituents in positions 2 and 4 of this ring. The analogs demonstrate low micromolar inhibition of the target proteases and cidal activity against Trypanosoma cruzi with up to two log selectivity indices in counterscreens with myoblasts. Fourteen compounds were active against Trypanosoma brucei at low to mid micromolar concentrations. During the optimization of 1a, structure-based design and prediction of physicochemical properties were employed to maintain potency against the enzymes while removing colloidal aggregator characteristics observed for some molecules in this series.

Structure-based design of δ-lactones for new antifungal drug development: susceptibility, mechanism of action, and toxicity.

Dermatophytes are the etiological agents of cutaneous mycoses, including the prevalent nail infections and athlete's foot. Candida spp. are opportunistic and emerging pathogens, causing superficial to deeper infections related to high mortality rates. As a consequence of prolonged application of antifungal drugs, the treatment failures combined with multidrug-resistance have become a serious problem in clinical practice. Therefore, novel alternative antifungals are required urgently. δ-Lactones have attracted great interest owing to their wide range of biological activity. This article describes the antifungal activity of synthetic δ-lactones against yeasts of the genus Candida spp. and dermatophytes (through the broth microdilution method), discusses the pathways by which the compounds exert this action (toward the fungal cell wall and/or membrane), and evaluates the toxicity to human leukocytes and chorioallantoic membrane (by the hen's egg test-chorioallantoic membrane). Two of the compounds in the series presented broader spectrum of antifungal activity, including against resistant fungal species. The mechanism of action was related to damage in the fungal cell wall and membrane, with specific target action dependent on the type of substituent present in the δ-lactone structure. The damage in the fungal cell was corroborated by electron microscopy images, which evidenced lysed and completely altered cells after in vitro treatment with δ-lactones. Toxicity was dose dependent for the viability of human leukocytes, but none of the compounds was mutagenic, genotoxic, or membrane irritant when evaluated at higher concentrations than MIC. In this way, δ-lactones constitute a class with excellent perspectives regarding their potential applications as antifungals.

New 99mTc-Labeled Digitoxigenin Derivative for Cancer Cell Identification.

In recent years, cardiac glycosides (CGs) have been investigated as potential antiviral and anticancer drugs. Digitoxigenin (DIG) and other CGs have been shown to bind and inhibit Na+/K+-adenosinetriphosphatase (ATPase). Tumor cells show a higher expression rate of the Na+/K+-ATPase protein or a stronger affinity towards the binding of CGs and are therefore more prone to CGs than non-tumor cells. Cancer imaging techniques using radiotracers targeted at specific receptors have yielded successful results. Technetium-99m (99mTc) is one of the radionuclides of choice to radiolabel pharmaceuticals because of its favorable physical and chemical properties along with reasonable costs. Herein, we describe a new Na+/K+-ATPase targeting radiotracer consisting of digitoxigenin and diethylenetriaminepentaacetic acid (DTPA), a bifunctional chelating ligand used to prepare 99mTc-labeled complexes, and its evaluation as an imaging probe. We report the synthesis and characterization of the radiolabeled compound including stability tests, blood clearance, and biodistribution in healthy mice. Additionally, we investigated the binding of the compound to A549 human non-small-cell lung cancer cells and the inhibition of the Na+/K+-ATPase by the labeled compound in vitro. The 99mTc-labeled DTPA-digitoxigenin (99mTc-DTPA-DIG) compound displayed high stability in vitro and in vivo, a fast renal excretion, and a specific binding towards A549 cancer cells in comparison to non-tumor cells. Therefore, 99mTc-DTPA-DIG could potentially be used for non-invasive visualization of tumor lesions by means of scintigraphic imaging.

Discovery and characterization of trypanocidal cysteine protease inhibitors from the 'malaria box'.

Chagas disease, Human African Trypanosomiasis, and schistosomiasis are neglected parasitic diseases for which new treatments are urgently needed. To identify new chemical leads, we screened the 400 compounds of the Open Access Malaria Box against the cysteine proteases, cruzain (Trypanosoma cruzi), rhodesain (Trypanosoma brucei) and SmCB1 (Schistosoma mansoni), which are therapeutic targets for these diseases. Whereas just three hits were observed for SmCB1, 70 compounds inhibited cruzain or rhodesain by at least 50% at 5 µM. Among those, 15 commercially available compounds were selected for confirmatory assays, given their potency, time-dependent inhibition profile and reported activity against parasites. Additional assays led to the confirmation of four novel classes of cruzain and rhodesain inhibitors, with potency in the low-to mid-micromolar range against enzymes and T. cruzi. Assays against mammalian cathepsins S and B revealed inhibitor selectivity for parasitic proteases. For the two competitive inhibitors identified (compounds 7 and 12), their binding mode was predicted by docking, providing a basis for structure-based optimization efforts. Compound 12 also acted directly against the trypomastigote and the intracellular amastigote forms of T. cruzi at 3 µM. Therefore, through a combination of experimental and computational approaches, we report promising hits for optimization in the development of new trypanocidal drugs.

Synthesis and structure-activity relationship studies of cruzain and rhodesain inhibitors.

Chagas disease and Human African trypanosomiasis (HAT) are important public health issues in Latin American and sub-Saharan African countries, respectively, and are responsible for a significant number of deaths. The drugs currently used to treat Chagas disease and HAT present efficacy, toxicity, and/or resistance issues; thus, there is a clear need for the discovery of novel targets and drug candidates to combat these diseases. In recent years, much effort has been made to find inhibitors of cruzain and rhodesain, which are promising targets for the design of novel trypanocidal compounds, since they are essential for parasite survival. Many reviews covering the design of novel cruzain and rhodesain inhibitors have been published; however, none have focused on the chemistry of the inhibitors. Thus, in the present work we reviewed the synthetic strategies and routes for the preparation of relevant classes of cruzain and rhodesain inhibitors. Perhaps the most important are the vinyl sulfone derivatives, and a very efficient synthetic strategy based on the Horner-Wadsworth-Emmons reaction was developed to yield these compounds. Modern approaches such as the asymmetric addition of substituted ethynyllithium to N-sulfinyl ketimines were used to produce the chiral alkynes that were employed in the preparation of important chiral triazole derivatives (potent cruzain inhibitors) and chiral HPLC resolution was used for the preparation of enantiopure 3-bromoisoxazoline derivatives (rhodesain inhibitors). Moreover, we also highlight the most important activity results and updated SAR results.

Design, synthesis and structure-activity relationship studies of a novel focused library of 2,3,4-substituted oxazolidines with antiproliferative activity against cancer cell lines.

In the present work we describe the synthesis and antiproliferative evaluation of a focused library of 30 novel oxazolidines designed by modification of N-substituent, by ring variation, by alkyl variation or by extension of the structure. It was noted that carbamate and N,O-aminal groups were essential for activity. In general, replacement of the phenyl ring with pyridinyl was not tolerated. However, the introduction of a second phenyl ring with an appropriate spacer at the 3- or 4-position of the first phenyl ring generally enhanced the cytotoxic profile. Among all the prepared compounds, 24 was the most potent compound found in this class, being active on four of five cancer cell lines and it was 5-fold and 10-fold more potent than the lead compounds against HL60 and JURKAT cells, respectively. In addition, it showed relevant activity against MCF-7 and HCT-116 cells, which were resistant to lead. Moreover, 24 showed little antiproliferative activity against VERO, indicating low toxicity to normal cells. Thus, this compound has the potential to be developed as an anticancer agent.