Antiplasmodial activity of chloroquine analogs against chloroquine-resistant parasites, docking studies and mechanisms of drug action

Submitted by Nuzia Santos ([email protected]) on 2015-03-02T17:19:49Z No. of bitstreams: 1 2014_121.pdf: 1273925 bytes, checksum: 09c618c236f85c7e45f2ad6a53efc484 (MD5)Approved for entry into archive by Nuzia Santos ([email protected]) on 2015-03-02T17:19:57Z (GMT) No. of bitstreams: 1 2014_121.pdf: 1273925 bytes, checksum: 09c618c236f85c7e45f2ad6a53efc484 (MD5)Approved for entry into archive by Nuzia Santos ([email protected]) on 2015-03-02T17:23:45Z (GMT) No. of bitstreams: 1 2014_121.pdf: 1273925 bytes, checksum: 09c618c236f85c7e45f2ad6a53efc484 (MD5)Made available in DSpace on 2015-03-02T17:23:45Z (GMT). No. of bitstreams: 1 2014_121.pdf: 1273925 bytes, checksum: 09c618c236f85c7e45f2ad6a53efc484 (MD5) Previous issue date: 2014Fundação Oswaldo Cruz. Centro de Pesquisas René Rachou. Laboratório de Malária. Belo Horizonte, MG, BrazilUniversidade Federal de Juiz de Fora. Instituto de Ciências Exatas. Departamento de Química. Juiz de Fora, MG, BrazilUniversidade Federal de Juiz de Fora. Instituto de Ciências Exatas. Departamento de Química. Juiz de Fora, MG, BrazilInstituto Militar de Engenharia. Laboratório de Modelagem Molecular Aplicada à Defesa Química e Biológica. Rio de Janeiro, RJ, BrazilFundação Oswaldo Cruz. Centro de Pesquisas René Rachou. Laboratório de Malária. Belo Horizonte, MG, BrazilBackground: Given the threat of resistance of human malaria parasites, including to artemisinin derivatives, new agents are needed. Chloroquine (CQ) has been the most widely used anti-malarial, and new analogs (CQAns) presenting alkynes and side chain variations with high antiplasmodial activity were evaluated. Methods: Six diaminealkyne and diaminedialkyne CQAns were evaluated against CQ-resistant (CQ-R) (W2) and CQ-sensitive (CQ-S) (3D7) Plasmodium falciparum parasites in culture. Drug cytotoxicity to a human hepatoma cell line (HepG2) evaluated, allowed to calculate the drug selectivity index (SI), a ratio of drug toxicity to activity in vitro. The CQAns were re-evaluated against CQ-resistant and -sensitive P. berghei parasites in mice using the suppressive test. Docking studies with the CQAns and the human (HssLDH) or plasmodial lactate dehydrogenase (PfLDH) enzymes, and, a β-haematin formation assay were performed using a lipid as a catalyst to promote crystallization in vitro. Results: All tested CQAns were highly active against CQ-R P. falciparum parasites, exhibiting half-maximal inhibitory concentration (IC50) values below 1 μΜ. CQAn33 and CQAn37 had the highest SIs. Docking studies revealed the best conformation of CQAn33 inside the binding pocket of PfLDH; specificity between the residues involved in H-bonds of the PfLDH with CQAn37. CQAn33 and CQAn37 were also shown to be weak inhibitors of PfLDH. CQAn33 and CQAn37 inhibited β-haematin formation with either a similar or a 2-fold higher IC50 value, respectively, compared with CQ. CQAn37 was active in mice with P. berghei, reducing parasitaemia by 100%. CQAn33, -39 and -45 also inhibited CQ-resistant P. berghei parasites in mice, whereas high doses of CQ were inactive. Conclusions: The presence of an alkyne group and the size of the side chain affected anti-P. falciparum activityin vitro. Docking studies suggested a mechanism of action other than PfLDH inhibition. The β-haematin assay suggested the presence of an additional mechanism of action of CQAn33 and CQAn37. Tests with CQAn34, CQAn37, CQAn39 and CQAn45 confirmed previous results against P. berghei malaria in mice, and CQAn33, 39 and 45 were active against CQ-resistant parasites, but CQAn28 and CQAn34 were not. The result likely reflects structure-activity relationships related to the resistant phenotype

Synthesis, Cytotoxicity, and Antileishmanial Activity of N,N'-Disubstituted Ethylenediamine and Imidazolidine Derivatives

This paper describes the preparation of N,N'-disubstituted ethylenediamine and imidazolidine derivatives and their in vitro biological activities against Leishmania species. Of the nine synthesized compounds, five displayed a good activity in both L. amazonensis and L. major promastigotes. The compounds 1,2-Bis(p-methoxybenzyl)ethylenediamine (4) and 1,3-Bis(p-methoxybenzyl)imidazolidines (5) showed the best activity on intracellular amastigotes, with IC50 values of 2.0 and 9.4 μ/mL, respectively. In addition, none of compounds were cytotoxic against mammalian cells. The leishmanicidal activity can be related with inhibition of polyamine synthesis and cellular penetration within biological membranes

Comparison of methods for the detection of biofilm production in coagulase-negative staphylococci

<p>Abstract</p> <p>Background</p> <p>The ability of biofilm formation seems to play an essential role in the virulence of coagulase-negative staphylococci (CNS). The most clearly characterized component of staphylococcal biofilms is the polysaccharide intercellular adhesin (PIA) encoded by the <it>icaADBC </it>operon. Biofilm production was studied in 80 coagulase-negative staphylococci (CNS) strains isolated from clinical specimens of newborns with infection hospitalized at the Neonatal Unit of the University Hospital, Faculty of Medicine of Botucatu, and in 20 isolates obtained from the nares of healthy individuals without signs of infection. The objective was to compare three phenotypic methods with the detection of the <it>icaA</it>, <it>icaD </it>and <it>icaC </it>genes by PCR.</p> <p>Findings</p> <p>Among the 100 CNS isolates studied, 82% tested positive by PCR, 82% by the tube test, 81% by the TCP assay, and 73% by the CRA method. Using PCR as a reference, the tube test showed the best correlation with detection of the <it>ica </it>genes, presenting high sensitivity and specificity.</p> <p>Conclusions</p> <p>The tube adherence test can be indicated for the routine detection of biofilm production in CNS because of its easy application and low cost and because it guarantees reliable results with excellent sensitivity and specificity.</p