Synthesis and Antileishmanial Activity of 1,2,4,5-Tetraoxanes against Leishmania donovani

A chemically diverse range of novel tetraoxanes was synthesized and evaluated in vitro against intramacrophage amastigote forms of Leishmania donovani. All 15 tested tetraoxanes displayed activity, with IC50 values ranging from 2 to 45 µm. The most active tetraoxane, compound LC140, exhibited an IC50 value of 2.52 ± 0.65 µm on L. donovani intramacrophage amastigotes, with a selectivity index of 13.5. This compound reduced the liver parasite burden of L. donovani-infected mice by 37% after an intraperitoneal treatment at 10 mg/kg/day for five consecutive days, whereas miltefosine, an antileishmanial drug in use, reduced it by 66%. These results provide a relevant basis for the development of further tetraoxanes as effective, safe, and cheap drugs against leishmaniasis.This research was funded by Fundação para a Ciência e a Tecnologia (FCT), and FEDER/COMPETE 2020-UE, through projects UID/Multi/04326/2019 (Centre of Marine Sciences-CCMAR) and PTDC/MAR-BIO/4132/2014.info:eu-repo/semantics/publishedVersio

Highly active ozonides selected against drug resistant malaria

Ever increasing multi-drug resistance by Plasmodium falciparum is creating new challenges in malaria chemotherapy. In the absence of licensed vaccines, treatment and prevention of malaria is heavily dependent on drugs. Potency, range of activity, safety, low cost and ease of administration are crucial issues in the design and formulation of antimalarials. We have tested three synthetic ozonides NAC89, LC50 and LCD67 in vitro and in vivo against multidrug resistant Plasmodium. In vitro, LC50 was at least 10 times more efficient inhibiting P. falciparum multidrug resistant Dd2 strain than chloroquine and mefloquine and as efficient as artemisinin (ART), artesunate and dihydroartemisinin. All three ozonides showed high efficacy in clearing parasitaemia in mice, caused by multi-drug resistant Plasmodium chabaudi strains, by subcutaneous administration, demonstrating high efficacy in vivo against ART and artesunate resistant parasites

Investigations into the Mechanism of Solvolysis of 3-aryloxybenzisothiazoles

The solvolysis of selected 3-aryloxybenzisothiazoles (6a-c; Figure 1) in alcohols has been theoretically investigated. The geometries of ethers 6a-c were fully optimized at the DFT(O3LYP) level, with the 6-31++G(d,p) and 6-311++G(3df,3pd) basis sets. Calculations including solvation effects were performed with the 6-31++G(d,p) basis set. Overall, theoretical values for bond lengths and angles around the central ether linkage in ethers 6a-c are very close, for the isolated molecule and in methanol, and are also very close to those obtained by X-ray crystallography, revealing that the nature of the substituent on the aryl system has a negligible effect on geometric parameters around the ether linkage. The same applies to charge distributions, predicted using the NPA approach. However, measured rate constants for the solvolysis of the same compounds in alcohols show that the rate is affected by the electron-withdrawing/-donating characteristics of the substituent on the aryl ring and by the polarity of solvent. Two general pathways were considered for the solvolysis of ethers 6: associative (addition-elimination) or dissociative (fragmentation-recombination) mechanisms. Molecular orbital calculations by means of polarized continuum model (PCM) reaction field predicted that solvolysis of ethers 6 prefers an addition-elimination mechanism. Calculations show also that a dissociative mechanism for the solvolysis of ethers 6a-c is energetically much more demanding than its addition-elimination counterpart and is therefore a highly improbable pathway for the solvolysis. In addition, it was found that the putative cation intermediate formed during a dissociative process should easily convert into its 2-cyanobenzenesulfone cation isomer, via cleavage of the S-N bond.Fundação para a Ciência e a Tecnologia, Portugal [PEst-C/MAR/LA0015/2013, PTDC/QUI-QUI/111879/2009]; QREN-COMPETE-UE; CCMAR; FCT [Pest-OE/QUI/UI0313/2014, PRAXIS XXI/BD/19973/99, SFRH/BD/90435/2012]info:eu-repo/semantics/publishedVersio

In vitro assessment of antimicrobial, antioxidant, and cytotoxic properties of Saccharin-Tetrazolyl and-Thiadiazolyl derivatives: the simple dependence of the pH value on antimicrobial activity

The antimicrobial, antioxidant, and cytotoxic activities of a series of saccharin-tetrazolyl and -thiadiazolyl analogs were examined. The assessment of the antimicrobial properties of the referred-to molecules was completed through an evaluation of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against Gram-positive and Gram-negative bacteria and yeasts. Scrutiny of the MIC and MBC values of the compounds at pH 4.0, 7.0, and 9.0 against four Gram-positive strains revealed high values for both the MIC and MBC at pH 4.0 (ranging from 0.98 to 125 µg/mL) and moderate values at pH 7.0 and 9.0, exposing strong antimicrobial activities in an acidic medium. An antioxidant activity analysis of the molecules was performed by using the DPPH (2,2-diphenyl-1-picrylhydrazyl) method, which showed high activity for the TSMT (N-(1-methyl-2H-tetrazol-5-yl)-N-(1,1-dioxo-1,2-benzisothiazol-3-yl) amine, 7) derivative (90.29% compared to a butylated hydroxytoluene positive control of 61.96%). Besides, the general toxicity of the saccharin analogs was evaluated in an Artemia salina model, which displayed insignificant toxicity values. In turn, upon an assessment of cell viability, all of the compounds were found to be nontoxic in range concentrations of 0-100 µg/mL in H7PX glioma cells. The tested molecules have inspiring antimicrobial and antioxidant properties that represent potential core structures in the design of new drugs for the treatment of infectious diseases.Funding Agency Portuguese Foundation for Science and Technology UID/QUI/00100/2019 UID/MULTI/04326/2019 -CCMAR Portuguese Foundation for Science and Technology SFRH/BPD/99851/2014 IST-ID/115/2018info:eu-repo/semantics/publishedVersio

1,2,4-Trioxolane and 1,2,4,5-Tetraoxane endoperoxides against old-world Leishmania parasites: in vitro activity and mode of action

Leishmaniasis remains one of the ten Neglected Tropical Diseases with significant morbidity and mortality in humans. Current treatment of visceral leishmaniasis is difficult due to a lack of effective, non-toxic, and non-extensive medications. This study aimed to evaluate the selectivity of 12 synthetic endoperoxides (1,2,4-trioxolanes; 1,2,4,5-tetraoxanes) and uncover their biochemical effects on Leishmania parasites responsible for visceral leishmaniasis. The compounds were screened for in vitro activity against L. infantum and L. donovani and for cytotoxicity in two monocytic cell lines (J774A.1 and THP-1) using the methyl thiazol tetrazolium assay. Reactive oxygen species formation, apoptosis, and mitochondrial impairment were measured by flow cytometry. The compounds exhibited fair to moderate anti-proliferative activity against promastigotes of the 2 Leishmania species, with IC50 values ranging from 13.0 ± 1.7 µM to 793.0 ± 37.2 µM. Tetraoxanes LC132 and LC138 demonstrated good leishmanicidal activity on L. infantum amastigotes (IC50 13.2 ± 5.2 and 23.9 ± 2.7 µM) with low cytotoxicity in mammalian cells (SIs 22.1 and 118.6), indicating selectivity towards the parasite. Furthermore, LC138 was able to induce late apoptosis and dose-dependent oxidative stress without affecting mithocondria. Compounds LC132 and LC138 can be further explored as potential antileishmanial chemotypes.info:eu-repo/semantics/publishedVersio

Utilização de compostos com atividade antimalárica no controlo de perkinsiose em bivalves

Outbreaks of protozoan agents such as Perkinsus olseni represent major losses for the shellfish producers, urging the development of measures to contain and decrease these episodes. Antimalarial drugs and selective inhibitors designed to target unique metabolic features of the parasite (metabolisms that are not replicated in the host, such as the folate, and shikimate pathways), have been successfully used in the laboratory to inhibit Perkinsus proliferation. However, due to specificities in Perkinsus species and the surrounding environment, development of drug candidates requires further optimization at the molecular level, to improve pharmacologic properties, as well as development of suitable tests and administration protocols for adequate use. Recent advances and future perspectives on the use endoperoxide-type antimalarials for perkinsosis therapy are presented and discussed.info:eu-repo/semantics/publishedVersio

New endoperoxides highly active in vivo and in vitro against artemisinin-resistant Plasmodium falciparum

Background: The emergence and spread of Plasmodium falciparum resistance to artemisinin-based combination therapy in Southeast Asia prompted the need to develop new endoperoxide-type drugs. Methods: A chemically diverse library of endoperoxides was designed and synthesized. The compounds were screened for in vitro and in vivo anti-malarial activity using, respectively, the SYBR Green I assay and a mouse model. Ring survival and mature stage survival assays were performed against artemisinin-resistant and artemisinin-sensitive P. falciparum strains. Cytotoxicity was evaluated against mammalian cell lines V79 and HepG2, using the MTT assay. Results: The synthesis and anti-malarial activity of 21 new endoperoxide-derived compounds is reported, where the peroxide pharmacophore is part of a trioxolane (ozonide) or a tetraoxane moiety, flanked by adamantane and a substituted cyclohexyl ring. Eight compounds exhibited sub-micromolar anti-malarial activity (IC50 0.3–71.1 nM), no cross-resistance with artemisinin or quinolone derivatives and negligible cytotoxicity towards mammalian cells. From these, six produced ring stage survival < 1% against the resistant strain IPC5202 and three of them totally suppressed Plasmodium berghei parasitaemia in mice after oral administration. Conclusion: The investigated, trioxolane–tetrazole conjugates LC131 and LC136 emerged as potential anti-malarial candidates; they show negligible toxicity towards mammalian cells, ability to kill intra-erythrocytic asexual stages of artemisinin-resistant P. falciparum and capacity to totally suppress P. berghei parasitaemia in mice.info:eu-repo/semantics/publishedVersio

Identification of clusters of asthma control: A preliminary analysis of the inspirers studies

This work was funded by ERDF (European Regional Development Fund) through the operations: POCI- -01-0145-FEDER-029130 (“mINSPIRERS—mHealth to measure and improve adherence to medication in chronic obstructive respiratory diseases - generalisation and evaluation of gamification, peer support and advanced image processing technologies”) co-funded by the COMPETE2020 (Programa Operacional Competitividade e Internacionalização), Portugal 2020 and by Portuguese Funds through FCT (Fundação para a Ciência e a Tecnologia).© 2020, Sociedade Portuguesa de Alergologia e Imunologia Clinica. All rights reserved. Aims: To identify distinct asthma control clusters based on Control of Allergic Rhinitis and Asthma Test (CARAT) and to compare patients’ characteristics among these clusters. Methods: Adults and adolescents (≥13 years) with persistent asthma were recruited at 29 Portuguese hospital outpatient clinics, in the context of two observational studies of the INSPIRERS project. Demographic and clinical characteristics, adherence to inhaled medication, beliefs about inhaled medication, anxiety and depression, quality of life, and asthma control (CARAT, >24 good control) were collected. Hierarchical cluster analysis was performed using CARAT total score (CARAT-T). Results: 410 patients (68% adults), with a median (percentile 25–percentile 75) age of 28 (16-46) years, were analysed. Three clusters were identified [mean CARAT-T (min-max)]: cluster 1 [27(24-30)], cluster 2 [19(14-23)] and cluster 3 [10(2-13)]. Patients in cluster 1 (34%) were characterised by better asthma control, better quality of life, higher inhaler adherence and use of a single inhaler. Patients in clusters 2 (50%) and 3 (16%) had uncontrolled asthma, lower inhaler adherence, more symptoms of anxiety and depression and more than half had at least one exacerbation in the previous year. Further-more, patients in cluster 3 were predominantly female, had more unscheduled medical visits and more anxiety symp-toms, perceived a higher necessity of their prescribed inhalers but also higher levels of concern about taking these inhalers. There were no differences in age, body mass index, lung function, smoking status, hospital admissions or specialist physician follow-up time among the three clusters. Conclusion: An unsupervised method based on CARAT--T, identified 3 clusters of patients with distinct, clinically meaningful characteristics. The cluster with better asthma control had a cut-off similar to the established in the validation study of CARAT and an additional cut-off seems to distinguish more severe disease. Further research is necessary to validate the asthma control clusters identified.publishersversionpublishe

Photoinduced reactivity in a Dispiro-1,2,4-trioxolane: Adamantane ring expansion and first direct observation of the long-lived triplet diradical intermediates

Dispiro-1,2,4-trioxolane, 1, an ozonide with efficient and broad antiparasitic activity, was synthesized and investigated using matrix isolation FTIR and EPR spectroscopies together with both B3LYP/6-311++G(3df, 3dp) and M06- 2X/6-311++G-(3df,3dp) theoretical methods. Irradiations (lambda >= 290 nm) of the matrix isolated 1 (Ar or N-2) afforded exclusively 4-oxahomoadamantan-5-one, 4, and 1,4-cyclohexanedione, 5. These results suggested that the reaction proceeded via a dioxygen-centered diradical intermediate, formed upon homolytic cleavage of the labile peroxide bond, which regioselectively isomerized to form the more stable (secondary carbon-centered)/oxygen-centered diradical. In situ EPR measurements during the photolysis of 1 deposited in a MeTHF-matrix led to the detection of signals corresponding to two triplet species, one of which was short-lived while the other proved to be persistent at 10 K. These observations strongly support the proposed mechanism for the photogeneration of 4 and 5, which involves intramolecular rearrangement of the intermediate diradical species 2 to afford the triplet diradical 3.Portuguese Science Foundation (FCT)Portuguese Foundation for Science and Technology [UID/QUI/0313/2019, UID/MULTI/04326/2019]COMPETE-EUFCTPortuguese Foundation for Science and TechnologyEuropean Commission [CCMAR/BI/0013/2017, PTDC/MAR-BIO/4132/2014, SFRH/BD/136246/2018, SFRH/BD/130407/2017]CCMar [PTDC/MAR-BIO/4132/2014]info:eu-repo/semantics/publishedVersio