Development and Evaluation of a Nanoemulsion Containing Ursolic Acid: a Promising Trypanocidal Agent : Nanoemulsion with Ursolic Acid Against T. cruzi

Over a hundred years after the discovery of Chagas disease, this ailment continues to affect thousands of people. For more than 40 years, only two drugs have been available to treat it. Ursolic acid is a naturally occurring terpene that has shown a good trypanocidal action. However, the hydrophobicity of this compound presents a challenge for the development of proper delivery systems. Nanostructured systems are a prominent in delivering lipophilic drugs. Thus, a nanoemulsion containing ursolic acid was developed and had its trypanocidal activity and cytotoxicity evaluated. Pseudo-ternary phase diagrams and hydrophilic-lipophilic balance (HLB) system were used in the development. The system was stable throughout 90 days of testing, as evidenced by turbidimetry analysis and measurements of the droplet size (57.3 nm) and polydispersity index (0.24). Fourier transform infrared spectroscopy and mass spectrometry evidenced drug's integrity in the formulation. An in vitro dissolution profile showed 75% of ursolic acid release after 5 min from the nanoemulsion into the alkaline dissolution medium, while only 20% could be released from a physical mixture after 2 h. Trypanocidal activity and cytotoxicity were evaluated on the CL Brener strain and LLC-MK2 (monkey kidney) fibroblast by chlorophenol red-β-D-galactoside (CPRG) method. Biological studies showed that the developed formulation was nontoxic and effective against replicant forms of the parasite. A stable and efficient nanoemulsion could be developed to improve the delivery of a promising drug to treat a threatening illness such as Chagas disease.

New uses for old complexes: The very first report on the trypanocidal activity of symmetric trinuclear ruthenium complexes

This work reports on the trypanocidal activity of a series of symmetric triruthenium complexes combined with azanaphthalene ligands of general formula [Ru₃O(CH₃COO)₆(L)₃]PF₆ (L=(1) quinazoline (qui), (2) 5-nitroisoquinoline (5-nitroiq), (3) 5-bromoisoquinoline (5-briq), (4) isoquinoline (iq), (5) 5-aminoisoquinoline (5-amiq), and (6) 5,6,7,8-tetrahydroisoquinoline (thiq)). All complexes within the series presented in vitro trypanocidal activity against both the trypomastigote and amastigote forms of T. cruzi. The IC₅₀ values obtained for complexes 1-6 ranged from 1.39 to 165.9μM for the trypomastigote form and from 1.06 to 53.16μM for the amastigote form. These values were lower than the values observed for the metallic core [Ru₃O(CH₃COO)₆(CH₃OH)₃]⁺ itself and for the free ligands in all cases. Remarkably, complex 6 displayed lower IC₅₀ values than the reference drug (benznidazole) for the acute (trypomastigote form) and chronic (amastigote form) phases of Chagas disease. These findings, combined with the low toxicity against healthy cells (LLK-MK₂ strain) and a high SI value (Selectivity Index >10) make complex 6 an excellent candidate for in vivo tests.

Anti-trypanosomal activity of non-peptidic nitrile-based cysteine protease inhibitors

The cysteine protease cruzipain is considered to be a validated target for therapeutic intervention in the treatment of Chagas disease. Anti-trypanosomal activity against the CL Brener strain of T. cruzi was observed in the 0.1 μM to 1 μM range for three nitrile-based cysteine protease inhibitors based on two scaffolds known to be associated with cathepsin K inhibition. The two compounds showing the greatest potency against the trypanosome were characterized by EC50 values (0.12 μM and 0.25 μM) that were an order of magnitude lower than the corresponding Ki values measured against cruzain, a recombinant form of cruzipain, in an enzyme inhibition assay. This implies that the anti-trypanosomal activity of these two compounds may not be explained only by the inhibition of the cruzain enzyme, thereby triggering a putative polypharmacological profile towards cysteine proteases.

Molecular Design, Synthesis and Trypanocidal Activity of Dipeptidyl Nitriles as Cruzain Inhibitors

A series of compounds based on the dipeptidyl nitrile scaffold were synthesized and assayed for their inhibitory activity against the T. cruzi cysteine protease cruzain. Structure activity relationships (SARs) were established using three, eleven and twelve variations respectively at the P1, P2 and P3 positions. A K_i value of 16 nM was observed for the most potent of these inhibitors which reflects a degree of non-additivity in the SAR. An X-ray crystal structure was determined for the ligand-protein complex for the structural prototype for the series. Twenty three inhibitors were also evaluated for their anti-trypanosomal effects and an EC₅₀ value of 28 μM was observed for the most potent of these. Although there remains scope for further optimization, the knowledge gained from this study is also transferable to the design of cruzain inhibitors based on warheads other than nitrile as well as alternative scaffolds.

Chagas disease is a parasitic infection with high morbidity and mortality that is endemic in much of Latin America where it remains a serious public health problem. With increased migration, Chagas disease represents an emerging worldwide challenge and there is an urgent, unmet need for safe and effective medication. The available drugs to treat Chagas disease may be effective in the acute phase of the disease, but efficacy in the chronic phase remains controversial. They can cause serious side effects that lead sufferers to abandon treatment. Using a hypothesis-driven approach to molecular design and drawing on cysteine protease cruzain structural information, we have mapped structure-activity relationships for a dipeptidyl nitrile scaffold and demonstrated that compounds are competitive inhibitors, bind reversibly and bear trypanocidal activity. The binding mode revealed by the crystal structure of the protein-ligand complex for one of the inhibitors shows that binding involves the formation of a covalent bond between the catalytic cysteine and the nitrile carbon. As such, we believe that our study represents a valuable step in the search for new drugs for the treatment of a neglected disease that continues to affect the lives of millions of people.

Preparation, characterization and evaluation of the in vivo trypanocidal activity of ursolic acid-loaded solid dispersion with poloxamer 407 and sodium caprate

Ursolic acid is a promising candidate for treatment of Chagas disease; however it has low aqueous solubility and intestinal absorption, which are both limiting factors for bioavailability. Among the strategies to enhance the solubility and dissolution of lipophilic drugs, solid dispersions are growing in popularity. In this study, we employed a mixture of the surfactants poloxamer 407 with sodium caprate to produce a solid dispersion containing ursolic acid aimed at enhancing both drug dissolution and in vivo trypanocidal activity. Compared to the physical mixture, the solid dispersion presented higher bulk density and smaller particle size. Fourier Transform Infrared Spectroscopy results showed hydrogen bonding intermolecular interactions between drug and poloxamer 407. X-ray diffractometry experiments revealed the conversion of the drug from its crystalline form to a more soluble amorphous structure. Consequently, the solubility of ursolic acid in the solid dispersion was increased and the drug dissolved in a fast and complete manner. Taken together with the oral absorption-enhancing property of sodium caprate, these results explained the increase of the in vivo trypanocidal activity of ursolic acid in solid dispersion, which also proved to be safe by cytotoxicity evaluation using the LLC-MK2 cell line.

Novel naphthoquinone derivatives and evaluation of their trypanocidal and leishmanicidal activities

Novel naphthoquinone derivatives were synthesized and tested for trypanocidal and leishmanicidal activities. Compound 11a was the most active against T. cruzi.

In vivo activity of ursolic and oleanolic acids during the acute phase of Trypanosoma cruzi infection

Reduction in the parasitemic levels of the Y strain of Trypanosoma cruzi in mice treated with oral or intraperitoneal ursolic (UA) and oleanolic (OA) acids was evaluated during the acute phase of Chagas' disease. Oral administration of UA and OA (50mg/kg/day) provided the most significant reduction in the parasitemic peak, while intraperitoneal administration of UA and OA did not significantly affect the biological activity of the Y strain of T. cruzi. Interleukin levels in mice treated by the intraperitoneal route were compared to untreated chagasic mice. Reduced γ-IFN levels and enhanced IL-10 concentrations potentially explain the exacerbated parasitemia. Our data suggests an immunosuppressive effect for UA and OA, which could interfere with host control of parasitemia. Optimal results were achieved with oral administration. This observation may be explained by the low intestinal absorption of UA and OA, could cause a reduced immune response and promote parasite control. Taken together, these data demonstrate that triterpenes could be interesting compounds to develop therapeutically for the treatment of Chagas' disease.

In vitro metabolism of grandisin, a lignan with anti-chagasic activity

Tetrahydrofuran lignans represent a well-known group of phenolic compounds capable of acting as antiparasitic agents. In the search for new medicines for the treatment of Chagas disease, one promising compound is grandisin which has shown significant activity on trypomastigote forms of Trypanosoma cruzi. In this work, the in vitro metabolism of grandisin was studied in the pig cecum model and by biomimetic phase I reactions, aiming at an ensuing a preclinical pharmacokinetic investigation. Although grandisin exhibited no metabolization by the pig microbiota, one putative metabolite was formed in a biomimetic model using Jacobsen catalyst. The putative metabolite was tested against T. cruzi revealing loss of activity in comparison to grandisin.

Trypanosoma cruzi: evaluation of (-)-cubebin derivatives activity in the messenger RNAs processing

No fully effective treatment has been developed since the discovery of Chagas' disease. Since drug-resistant Trypanosoma cruzi strains are occurring and the current therapy is effective in the acute phase but with various adverse side effects, more studies are needed to characterize the susceptibility of T. cruzi to new drugs. Pre-mRNA maturation in trypanosomatids occurs through a process called trans-splicing, which is unusual RNA processing reaction, and it implies the processing of polycistronic transcription units into individual mRNAs; a short transcript spliced leader (SL RNA) is trans-spliced to the acceptor pre-mRNA, giving origin to the mature mRNA. Cubebin derivatives seem to provide treatments with less collateral effects than benznidazole and showed similar or better trypanocidal activities than benznidazole. Therefore, the cubebin derivatives ((-)-6,6'-dinitrohinokinin (DNH) and (-)-hinokinin (HQ)) interference in the mRNA processing was evaluated using T. cruzi permeable cells (Y and BOL (Bolivia) strains) following by RNase protection reaction. These substances seem to intervene in any step of the RNA transcription, promoting alterations in the RNA synthesis, even though the RNA processing mechanism still occurs. Furthermore, HQ presented better activity against the parasites than DNH, meaning that BOL strain seems to be more resistant than Y.

Trypanocidal activity and acute toxicity assessment of triterpene acids

The present study evaluates the in vitro and in vivo trypanocidal activity of ursolic acid and oleanolic acid against the Bolivia strain of Trypanosoma cruzi. Their acute toxicity is also assessed on the basis of median lethal dose (DL50) determination and quantification of biochemical parameters. Ursolic acid is the most active compound in vitro, furnishing IC50 of 25.5 microM and displaying 77% of trypomastigote lysis at a concentration of 128 microM. In agreement with in vitro assays, the results obtained for the in vivo assay reveals that ursolic acid (at a dose of 20 mg/Kg/day) provides the most significant reduction in the number of parasites at the parasitemic peak. Results concerning the LD50 assay and the biochemical parameters evaluated in the present study demonstrate that these substances can be safely used on an experimental basis.

New method for quantification of Trypanosoma cruzi in animal's tissue in the chronic phase of experimental Chagas' disease

We developed a new method for the quantification of parasites in tissue. Trypanosoma cruzi strain CL parasites were genetically engineered to express the Escherichia coli beta-galactosidase gene, lacZ and this enzyme is able to catalyze a colorimetric reaction with chlorophenol red beta-D: galactopyranoside (CPRG) as the substrate. The animals were infected with clone CL Brener strain B5 of T. cruzi and treated with benznidazole in order to verify the reduction in the number of parasites in tissue study by quantifying the enzyme beta-galactosidase. The assay demonstrates a reduction in the number of parasites in the groups treated. Thus, this test can be used to test other substances with the aim of verifying the effectiveness in the chronic phase of experimental Chagas' disease.

Trypanocidal, leishmanicidal and antifungal potential from marine red alga Bostrychia tenella J. Agardh (Rhodomelaceae, Ceramiales)

Specimens of the red alga Bostrychia tenella J. Agardh (Rhodomelaceae, Ceramiales) were collected from the São Paulo coast and submitted to room temperature solvent extraction. The resulting extract was fractionated by partitioning with organic solvent. The n-hexane (BT-H) and dichloromethane (BT-D) fractions showed antiprotozoal potential in biological tests with Trypanosoma cruzi and Leishmania amazonensis and presented high activity in an antifungal assay with the phytopathogenic fungi Cladosporium cladosporioides and Cladosporium sphaerospermum. Chromatography methods were used to generate subfractions from BT-H (H01 to H11) and from BT-D (D01 to D19). The subfractions were analyzed by gas chromatography-mass spectrometry (GC/MS), and the substances were identified by retention index (Kovats) and by comparison to databases of commercial mass spectra. The volatile compounds found in marine algae were identified as fatty acids, low molecular mass hydrocarbons, esters and steroids; some of these have been previously described in the literature based on other biological activities. Moreover, uncommon substances, such as neophytadiene were also identified. In a trypanocidal assay, fractions BT-H and BT-D showed IC(50) values of 16.8 and 19.1 microg/mL, respectively, and were more active than the gentian violet standard (31 microg/mL); subfractions H02, H03, D01 and D02 were active against L. amasonensis, exhibiting IC(50) values of 1.5, 2.7, 4.4, and 4.3 microg/mL, respectively (standard amphotericin B: IC(50)=13 microg/mL). All fractions showed antifungal potential. This work reports the biological activity and identification of compounds by GC/MS for the marine red alga B. tenella for the first time.

Trypanocidal and antifungal activities of p-hydroxyacetophenone derivatives from Calea uniflora (Heliantheae, Asteraceae)

The dichloromethane extract of underground parts of Calea uniflora (Heliantheae, Asteraceae) exhibited trypanocidal and antifungal activities. Four p-hydroxyacetophenone derivatives were isolated as the main compounds: 2-senecioyl-4-(hydroxyethyl)-phenol (1), 2-senecioyl-4-(angeloyloxy-ethyl)-phenol (2), and two new derivatives, 2-senecioyl-4-(methoxyethyl)-phenol (3) and 2-senecioyl-4-(pentadecanoyloxyethyl)-phenol (4). 1 and 4 were active towards Trypanosoma cruzi trypomastigotes, reducing their number by 70 and 71% at 500 μg mL−1, whereas 2 and 3 were inactive. All the compounds tested showed antifungal activity with minimal inhibitory concentration values between 500 and 1000 μg mL−1 against pathogenic Candida spp. and dermatophytes. The isolation, structure elucidation, NMR spectral assignments and bioactivity results of these compounds are reported.

(-)-Hinokinin-loaded poly(D,-lactide-co-glycolide) microparticles for Chagas disease

The (-)-hinokinin display high activity against Trypanosoma cruzi in vitro and in vivo. (-)-Hinokinin-loaded poly(D,L-lactide-co-glycolide) microparticles were prepared and characterized in order to protect (-)-hinokinin of biological interactions and promote its sustained release for treatment of Chagas disease. The microparticles contain (-)-hinokinin were prepared by the classical method of the emulsion/solvent evaporation. The scanning electron microscopy, light-scattering analyzer were used to study the morphology and particle size, respectively. The encapsulation efficiency was determined, drug release studies were kinetically evaluated, and the trypanocidal effect was evaluated in vivo. (-)-Hinokinin-loaded microparticles obtained showed a mean diameter of 0.862 microm with smooth surface and spherical shape. The encapsulation efficiency was 72.46 +/- 2.92% and developed system maintained drug release with Higuchi kinetics. The preparation method showed to be suitable, since the morphological characteristics, encapsulation efficiency, and in vitro release profile were satisfactory. In vivo assays showed significant reduction of mice parasitaemia after administration of (-)-hinokinin-loaded microparticles. Thus, the developed microparticles seem to be a promising system for sustained release of (-)-hinokinin for treatment of Chagas disease.

Melatonin and dehydroepiandrosterone combination: does this treatment exert a synergistic effect during experimental Trypanosoma cruzi infection?

Previous studies showed that melatonin or dehydroepiandrosterone (DHEA) enhances the immune response against parasitic pathogens. The present study investigated the in vitro activity of melatonin combined with DHEA in a period of 24 hr during the course of in vivo T. cruzi infection. The in vitro activity of melatonin or DHEA alone, as well as together, were tested for the trypomastigote forms (doses ranging from 0.5 to 128 microm). In vitro, neither melatonin nor DHEA alone had any activity against trypomastigote forms, although when the highest concentration of combined melatonin and DHEA was used, it was active against the trypomastigote forms of the parasite. However, for this concentration, a quite toxicity on peritoneal macrophages was observed. For in vivo evaluation, male Wistar rats were infected with the Y strain of T. cruzi. They were orally treated with 10 mg/kg body weight/day of melatonin and subcutaneously with 40 mg/kg body weight/day of DHEA. Treatment with melatonin, DHEA and the association showed a significant reduction in the number of blood trypomastigotes during the acute phase of infection as compared to untreated animals (P < 0.05). A significant increase in the number of macrophages and nitric oxide (NO) concentrations were observed during the peak of parasitaemia with melatonin alone or combined with DHEA. However, with DHEA alone the highest concentration of NO was observed (P < 0.05). Moreover, DHEA treatment increased TNF-alpha levels during the infection (P < 0.05). These results show that melatonin, DHEA or the combination of both reduces parasitemia during the acute phase of infection. The combined action of both molecules did not exert a synergic action on the host's ability to fight infection, and it seems that among all treatments DHEA induces a more efficient immune response.

Trypanocidal activity of pimarane diterpenes from Viguiera arenaria (Asteraceae)

Five structurally related pimarane diterpenes isolated from the roots of Viguiera arenaria and a further compound obtained by chemical derivatization were evaluated in vitro against the trypomastigote forms of Trypanosoma cruzi. The natural compound ent-15-pimarene-8 beta,19-diol and the derivative ent-8(14),15-pimaradiene-3beta-acetoxy showed the highest trypanocidal activity, displaying IC(50) values of 116.5 +/- 1.21 and 149.3 +/- 1.07 microM, respectively, while the positive control, violet gentian, showed an IC(50) of 76 microM. Based on the results, it can be concluded that minor structural differences among the tested diterpenes influence significantly the trypanocidal activity, thus bringing new perspectives to the establishment of structure-activity relationships among this type of metabolites to the treatment of Chagas' disease.

Trypanocidal activity of limonoids and triterpenes from Cedrela fissilis

Chagas' disease is an illness that affects millions of people in Central and South America. The search for both a prophylactic drug to be added to human blood as well as a safe and reliable therapeutic drug are greatly needed to control such disease. Herein, we report the trypanocidal activity of 15 crude extracts and 14 compounds (limonoids and triterpenes) as well as the isolation of 25 known compounds (6 limonoids, 12 triterpenes, 1 sesquiterpene, 5 steroids, and 1 flavonoid) from Cedrela fissilis. The present study shows that this plant is a promising source of active compounds for the control of Chagas' disease. The inhibitory activity found for odoratol indicates that it is potentially useful as an alternative for the chemoprophylactic gentian violet.

Is there an association between bruxism and intestinal parasitic infestation in children?

PURPOSE

Multiple factors have been considered in the etiology of bruxism in pediatric patients, among which are infestations by intestinal parasites suggested by some authors. No empirical evidence exists, however, of such association. Therefore, this study's purpose was to investigate the existence of an association between bruxism and intestinal parasitic infestation in children.

METHODS

Fifty-seven 6- to 11-year-olds (30 cases and 27 controls) who had not used anthelminthics 2 months before the baseline examination were enrolled in the study. A diagnosis of bruxism was based on an intraoral clinical examination performed by a single trained examiner and on the parent/guardian's report of any perceived parafunctional habits (questionnaire-based interview). Bruxism cases were defined as those children with a report of currently perceived habits of eccentric or centric bruxism (tooth-grinding and tooth-clenching, respectively) combined with clinical evidence of nonphysiologic wear facets. The volunteers were required to collect 3 fecal samples (1 every 2 to 3 days). Parasitologic analysis was performed using the spontaneous sedimentation method. Data gathered from the intraoral clinical examination, questionnaire, and parasitologic analysis were tabulated and submitted to statistical analysis using the chi-square test and student's t test.

RESULTS

Intestinal parasitic infestation was observed in 30% (N=9) of cases and 41% (N=11) of controls, but no statistically significant association was observed (P=.40).

CONCLUSION

This study's findings do not support the existence of an association between intestinal parasitic infestation and bruxism among the evaluated pediatric population.

[Histometry of the sublingual gland in male and female mice (Mus musculus) infected with the RAL strain of the Chagas parasite, Trypanosoma cruzi]

The aim of this work was to analyze histologically and histometrically the sublingual gland of mice infected with the RAL strain of T. cruzi, according to the sex. Swiss mice (Mus musculus) were inoculated with 2 x 10(4) blood trypomastigotes of the RAL strain of T. cruzi. In the peak of the parasitemia (12th day) the mice were sacrificed, and the sublingual glands were fixed in ALFAC. HE-stained histological sections were evaluated histometrically. The parasitemia was higher in females. Histopatologically, acini of the infected animals were smaller, with scanty production of secretion, and smaller striated ducts. The nuclei of the demilunes were smaller and showed amastigote nests in the cytoplasm. Karyometrically, nuclei of the acini, demilunes and striated ducts were smaller in the infected mice. Stereologically, it was observed that relative volumes of acini and ducts were smaller and, inversely, relative volumen were greater for the conjunctive tissue in the infected males. The surface densities of acini and ducts were bigger and the diameter and thickness of the wall were smaller in this group. On the other hand, relative volume of acini was smaller and those of the ducts and conjunctive tissue were bigger in the infected females. The diameter and thickness of the wall of acini were smaller, and those of the striated ducts were bigger in this group. The RAL strain of T. cruzi caused general atrophy in the sublingual gland, with numerous nests of parasites in the glandular parenchyma.