Synthesis and Antitrypanosomal and Mechanistic Studies of a Series of 2-Arylquinazolin-4-hydrazines: A Hydrazine Moiety as a Selective, Safe, and Specific Pharmacophore to Design Antitrypanosomal Agents Targeting NO Release.

Nitric oxide (NO) represents a valuable target to design antitrypanosomal agents by its high toxicity against trypanosomatids and minimal side effects on host macrophages. The progress of NO-donors as antitrypanosomal has been restricted by the high toxicity of their agents, which usually is based on NO-heterocycles and metallic NO-complexes. Herein, we carried out the design of a new class of NO-donors based on the susceptibility of the hydrazine moiety connected to an electron-deficient ring to be reduced to the amine moiety with release of NO. Then, a series of novel 2-arylquinazolin-4-hydrazine, with the potential ability to disrupt the parasite folate metabolism, were synthesized. Their in vitro evaluation against Leishmania and Trypanosoma cruzi parasites and mechanistic aspects were investigated. The compounds displayed significant leishmanicidal activity, identifying three potential candidates, that is, 3b, 3c, and 3f, for further assays by their good antiamastigote activities against Leishmania braziliensis, low toxicity, non-mutagenicity, and good ADME profile. Against T. cruzi parasites, derivatives 3b, 3c, and 3e displayed interesting levels of activities and selectivities. Mechanistic studies revealed that the 2-arylquinazolin-4-hydrazines act as either antifolate or NO-donor agents. NMR, fluorescence, and theoretical studies supported the fact that the quinazolin-hydrazine decomposed easily in an oxidative environment via cleavage of the N-N bond to release the corresponding heterocyclic-amine and NO. Generation of NO from axenic parasites was confirmed by the Griess test. All the evidence showed the potential of hydrazine connected to the electron-deficient ring to design effective and safe NO-donors against trypanosomatids.

In vitro evaluation and in vivo efficacy of nitroimidazole-sulfanyl ethyl derivatives against Leishmania (V.) braziliensis and Leishmania (L.) mexicana.

The aim of this study was to synthesize several small molecules of the type 5-nitroimidazole-sulfanyl and evaluate biological properties against the main Leishmania species that cause cutaneous leishmaniasis in Venezuela. Final compounds 4-7 were generated through simple nucleophilic substitution of 1-(2-chloroethyl)-2-methyl-5-nitroimidazole 3 with 2-mercaptoethanol, 1-methyl-2-mercaptoethanol, and 2-thyolacetic acid derivative. Compound 8 was synthesized via a coupling reaction between 7 and (S)-Methyl 2-amino-4-methylpentanoate hydrochloride. The inhibitory concentrations of (3, 4, 7, 8) against Leishmania (L.) mexicana and (V.) braziliensis in promastigotes and experimentally infected macrophages were determined by in vitro activity assays. Compounds 7 and 8 shown high activity against both species of Leishmania and were selected for the in vivo evaluation. Animals were infected with promastigotes of the two species and divided into four groups of ten (10) animals and a control group. Intralesional injection way was used for the treatment. The parasitological diagnostic after treatment was obtained by PCR using species specific oligonucleotides. The two Leishmania species were susceptible to compounds 7 and 8 in vivo assays. The results indicated that both compounds reduce significantly (96%) the size of the lesion and cure 63% of the mice infected with L (L) mexicana or L (V) braziliensis as was determined by PCR. The results are indicating that both compounds may represent an alternative treatment for these two Leishmania species.

Parasitological status of vicuñas (Vicugna vicugna) from southeastern Peru and its relationship with fiber quality.

We aim to describe the parasitic population in vicuñas from three Andean communities and its relationship with fiber quality using 115 fecal and 22 fiber samples, classified according to sex, age, body condition score, and management system. Coproparasitologic diagnostic revealed that 84.4% of animals presented at least one type of parasite egg/oocyst. Most frequent parasite egg/oocyst were Strongyle-type eggs (54.8%) and Eimeria punoensis (38.3%). Wild vicuñas had a higher prevalence of Strongyle-type eggs (91.4%) than semi-captive (38.8%) animals, and age was significative to Eimeria infection; crias had the highest frequency (100%) when compared to yearlings (84.2%) and adults (49.4%). Larvae identification revealed a strong influence of domestic animals on vicuña parasite community, presenting the first report of Bunostomum phlebotomum and Gaigeria pachyscelis in vicuñas from southeastern Peru. Females had a significantly finer diameter of fiber (13.05 ± 0.73 µm) than males (14.22 ± 1.22 µm), and infection with Eimeria spp. affected negatively fiber diameter and resistance. Our results provide data for disease surveillance and encourage further parasitological studies in vicuñas.

Antileismanial activity, mechanism of action study and molecular docking of 1,4-bis(substituted benzalhydrazino)phthalazines.

To identify new agents for the treatment of American cutaneous leishmaniasis, a series of eight 1,4-bis(substituted benzalhydrazino)phthalazines was evaluated against Leishmania braziliensis and Leishmania mexicana parasites. These compounds represent a disubstituted version of the 1-chloro-4-(monoaryl/heteroarylhydranizyl)phthalazine that exhibited a significant response against L. braziliensis according to our previous findings. Two disubstituted phthalazines 3b and 3f were identified as potential antileishmanial agents against L. braziliensis parasites, exhibiting a submicromolar IC50 response of 2.37 and 7.90 µM on the promastigote form, and of 1.82 and 4.56 µM against intracellular amastigotes, respectively. In particular, compound 3b showed interesting responses against amastigote isolates from reference, glucantime-resistant and clinical human strains, which were by far superior to the biological response found for the glucantime drug. With regard to the toxicity results, both 3b and 3f exhibited moderate LD50 values against murine macrophages (BMDM), with good selectivity indexes on promastigotes and intracellular amastigotes of L. braziliensis. A comparison of biological response was established between the monosubstituted and disubstituted versions of these benzalhydrazino-phthalazines. Easy synthetic procedure and significant response against amastigote strains including against resistant lines made compound 3b a potential candidate for further pharmacokinetic and in vivo experiments as antileishmanial agent, and as a platform for further structural optimization. Mechanism-of-action studies and molecular docking simulations discarded to inhibition of superoxide dismutase as possible mode of action.

Identification of dehydroxy isoquine and isotebuquine as promising antileishmanial agents.

Traditional antimalarial drugs based on 4-aminoquinolines have exhibited good antiproliferative activities against Leishmania parasites; however, their clinical use is currently limited. To identify new 4-aminoquinolines to combat American cutaneous leishmaniasis, we carried out a full in vitro evaluation of a series of dehydroxy isoquines and isotebuquines against two Leishmania parasites such as Leishmania braziliensis and Leishmania mexicana. First, the antiproliferative activity of the quinolines was studied against the promastigote forms of L. braziliensis and L. mexicana parasites, finding that five of them exhibited good antileishmanial responses with micromolar IC50 values ranging from 3.84 to 10 µM. A structure-activity relationship analysis gave evidence that a piperidine or a morpholine attached as N-alkyamino terminal substituent as well as the inclusion of an extra phenyl ring attached at the aniline ring of the isotebuquine core constitute important pharmacophores to generate the most active derivatives, with antileishmanial responses by far superior to those found for the reference drug, glucantime. All compounds showed a relatively low toxicity on human dermis fibroblasts, with CC50 ranging from 69 to >250 µM. The five most active compounds displayed moderate to good antileishmanial activity against the intracellular amastigote form of L. braziliensis, compared to the reference drug. In particular, compound 2j was identified as the most potent agent against antimony-resistant amastigotes of L. braziliensis with acceptable biological response and selectivity, emerging as a promising candidate for further in vivo antileishmanial evaluation. Diverse mechanism-of-action studies and molecular docking simulations were performed for the most active 4-aminoquinoline.

2-Aryl-quinazolin-4(3H)-ones as an inhibitor of leishmania folate pathway: In vitro biological evaluation, mechanism studies and molecular docking.

To identify new agents for the American Cutaneous Leishmaniasis treatment, a series of 2-aryl-quinazolin-4(3H)-ones were tested against L. mexicana, L. braziliensis and L. amazonensis parasites as potential inhibitor of folic metabolism pathway. In general, the L. braziliensis and L. mexicana promastigote parasites were more sensitive to the action of the quinazolinones than L. amazonensis. The most active derivatives showed low-micromolar EC50 ranging from 4 to 10 µM, being 1.3 to 4 fold more potent than glucantime reference drug. A complete in vitro evaluation on intracellular amastigote, axenic amastigote and murine peritoneal macrophage were performed for the most active derivatives. The compounds 2j, 2h, 2t and 2u displayed acceptable responses against intracellular amastigote compared to reference drug, excellent antileishmanial activities against axenic amastigote (LD50 ranging from 1 to 4 µM) and relative low toxicities on peritoneal macrophages. To validate the efficacy of these four derivatives, an in vitro evaluation was performed against an antimony-resistant amastigote strain; identifying to 2h and 2u as promising antileishmanial leads for further pharmacokinetics and in vivo studies. Experimental mechanism assays putted in evidences that the most active compounds act as folate inhibitor. A tentative molecular docking on pteridine reductase 1 (PTR1) enzyme showed that the most active quinazolinones 2j and 2t are located in almost identical place compared with methotrexate reference into active site.

Antileishmanial activity, structure-activity relationship of series of 2-(trifluoromethyl)benzo[b][1,8]naphthyridin-4(1H)-ones.

Trifluoromethyl-substituted quinolones and their analogues have emerged as an interesting platform in the last 6 years to design antiparasite agents. Many of their derivatives have been demonstrated to display excellent efficacy against flagellate parasites such as Plasmodium spp. In order to identify new analogues of trifluoromethyl-substituted quinolones to treat the American cutaneous leishmaniasis, we evaluated the antiproliferative activity of a series of 2-(trifluoromethyl)benzo[b]-[1,8]naphthyridin-4(1H)-ones on the Leishmania braziliensis and Leishmania mexicana parasites. The mentioned derivatives have never been evaluated against any parasite strain. In general, an in vitro evaluation on L.(L)mexicana and L.(V)braziliensis showed that L.(L)mexicana was more sensitive to the action of the compounds than L.(V)braziliensis, either in the promastigote or in the amastigote form. Five compounds exhibited moderate efficacy against L.(L)mexicana promastigotes, with IC50 values ranging from 9.65 to 14.76 µM. From the mentioned molecules, three compounds, 1e, 1f, and 1h, showed a discrete response against axenic and intracellular amastigotes, with LD50 values between 19 and 24 µM. Moreover, an in vitro evaluation was performed on an antimony-resistant amastigote strain and a human isolate amastigote strain. These three compounds showed discrete toxicity on peritoneal macrophages; however, their relatively good antiamastigote response compared to the drug glucantime promoted our trifluoromethyl-substituted benzo[b][1,8]naphthyridin-4(1H)-ones as a potential platform to design potent antileishmanial agents.