or L. Leon

Antileishmanial activity of lapachol analogues

The antileishmanial activity of lapachol, isolapachol, and dihydrolapachol, along with soluble derivatives (potassium salt) and acetate was obtained. All the compounds were assayed against metacyclic promastigotes of two different species of Leishmania associated to tegumentar leishmaniasis: L. amazonensis and L. braziliensis. All compounds presented significant activity, being isolapachol acetate the most active against promastigotes, with IC50/24h = 1.6 +/- 0.0 microg/ml and 3.4 +/- 0.5 microg/ml for, respectively, L. amazonensis and L. braziliensis. This compound was also assayed in vivo against L. amazonensis and showed to be active. Its toxicity in vitro was also established, and at concentration similar to the IC50, no toxicity was evidenced. In all experiments, pentamidine isethionate was used as a reference drug. The present results reinforce the potential use of substituted hydroxyquinones and derivatives as promising antileishmanial drugs and suggest a continuing study within this class of compounds.

Antimicrobial and antileishmanial activity of essential oil from the leaves of Annona foetida (Annonaceae)

bicyclogermacrene (35.12%), (E)-caryophyllene (14.19%) and α-copaene (8.19%). The antimicrobial and antileishmanial activities were investigated. The oil showed potent antimicrobial activity against Candida albicans and Rhodococcus equi. The oil also showed significant antileishmanial activity, giving the best results against Leishmania guyanensis. A preliminary cytotoxicity assay for this oil was carried out on hamster and mice (Balb/c) peritoneal macrophages. The results obtained were similar to pentamidine and considered not to be cytotoxic to macrophages.

Activity of Brazilian and Bulgarian propolis against different species of Leishmania

Extracts of propolis samples collected in Brazil and Bulgaria were assayed against four Leishmania species--Leishmania amazonensis, L. braziliensis, L. chagasi from the New World, and L. major from the Old World--associated to different clinical forms of leishmaniasis. The composition of the extracts has been previously characterized by high temperature high resolution gas chromatography coupled to mass spectrometry. Considering the chemical differences among the extracts and the behavior of the parasites, it was observed significant differences in the leishmanicidal activities with IC50/1 day values in the range of 2.8 to 229.3 microg/ml . An overall analysis showed that for all the species evaluated, Bulgarian extracts were more active than the ethanol Brazilian extract. As the assayed propolis extracts have their chemical composition determined it merits further investigation the effect of individual components or their combinations on each Leishmania species.

Studies on the effectiveness of diarylheptanoids derivatives against Leishmania amazonensis

In a previous work we demonstrated that diarylheptanoids extracted from Centrolobium sclerophyllum are very active against Leishmania amazonensis promastigotes. In order to continue our studies with these class of compounds, we decided to evaluate the activity of several diarylheptanoids derived from curcumin (diferuloyl methane) against the extracellular form (promastigotes) of L. amazonensis. Furthermore, an experiment against the intracellular form of the parasite (amastigotes) was carried out, comparing the most active compound among the curcumin derivatives (the methylcurcumin) with des-O-methylcentrolobine, the most active diarylheptanoid derived from C. sclerophyllum.

Anti-leishmanial activity of alkaloidal extract from Aspidosperma ramiflorum

Infections due to protozoa of the genus Leishmania are a major worldwide health problem, with high endemicity in developing countries. The drugs of choice for the treatment of leishmaniasis are the pentavalent antimonials (SbV), which present renal and cardiac toxicity. Besides, the precise chemical structure and mechanism of action of these drugs are unknown up to date. In order to find new drugs against leishmaniasis, we have been studying extracts of Brazilian trees. In the present study, we have evaluated the effectiveness of an alkaloid extract of Aspidosperma ramiflorum Muell. Arg. (Apocynaceae), against the extracellular forms promastigotes of L. (L.) amazonensis and L. (V.) braziliensis. The alkaloid extract of A. ramiflorum was much more effective against L. (L.) amazonensis (LD50 < 47 microg/ml) than L. (V.) braziliensis. Based on these in vitro results against L. (L.) amazonensis new studies should be made to find the compounds with anti-leishmanial activity.

Trypanosoma cruzi in the opossum Didelphis marsupialis: Parasitological and serological follow-up of the acute infection

The opossum Didelphis marsupialis is known to be among the most important wild reservoirs of Trypanosoma cruzi and one in which the trypanosome may go through both the usual vertebrate intracellular cycle in its tissues and an extracellular cycle in the lumen of its scent glands. The species is highly resistant to heavy inocula and, depending on the parasite strain, experimental infections may be permanent or self limited. Aiming to understand the mechanisms involved in this parasite-host interaction we made a study of the acute phase of infection with different T. cruzi strains. Strains F, G-49 and G-327 produced durable infections with relatively high parasitemia and invasion of the scent glands, while equivalent inocula of the Y strain resulted in scanty parasitemia of short duration, no invasion of the SG, and no evidence of persistent parasitism. A smaller inoculum of G-49 produced only subpatent though persistent parasitemia and no invasion of the scent glands. The humoral immune response was less marked in the Y group; among the other groups IgM and IgG antibodies increased to high levels, higher in the G-49 group. The increase in IgG coincided with a drop of parasitemia to subpatent levels. Two opossums inoculated directly in the scent glands with culture forms of the Y strain had a short-lived subpatent parasitemia, but the parasites remained in the glands and serum Ig antibodies reached high levels. Immunoblot analysis showed that the sera of the inoculated opossums recognized few T. cruzi antigens (more in the F strain) in comparison with those of mice. However, with the only exception of those subcutaneously inoculated with the Y strain and including two naturally infected specimens, all the opossums sera recognized a 90-kDa peptide in all T. cruzi strains. Our results confirm that opossums are able to selectively eliminate some strains of T. cruzi and indicate that the mechanism involved in this selection is probably not related to the humoral immune response. In infections by strains that are able to establish a permanent foothold in opossum tissues, there are indications that IgG antibodies participate in the control of the parasite population of the acute phase but are unable to prevent the chronic phase. It was once more demonstrated that the opossum infected scent glands function as diffusion chambers for parasite antigens but that, on the other hand, the parasites are here protected against the mechanisms developed by the host to control their population.

Nitric oxide biosynthesis by Leishmania amazonensis promastigotes containing a high percentage of metacyclic forms

Due to the diversity of its physiological and pathophysiological functions and general ubiquity, the study of nitric oxide (NO) has become of great interest. In this work, it was demonstrated that Leishmania amazonensis promastigotes produces NO, a free radical synthesized from l-arginine by nitric oxide synthase (NOS). A soluble NOS was purified from L. amazonensis promastigotes by affinity chromatography (2′, 5′-ADP-agarose) and on SDS-PAGE the enzyme migrates as a single protein band of 116.2 (±6) kDa. Furthermore, the presence of a constitutive NOS was detected through indirect immunofluorescence using anti-cNOS and in NADPH consumption assays. The present work show that NO production, detected as nitrite in culture supernatant, is prominent in promastigotes preparations with high number of metacyclic forms, suggesting an association with the differentiation and the infectivity of the parasite.

Comparative analysis of the nitric oxide production by Leishmania sp.

The present report explores a comparative analysis of nitric oxide (NO·) production by three different species of Leishmania (L. amazonensis, L. braziliensis and L. chagasi). Among these species, L. braziliensis produced the highest amount of NO·, measured in the supernatants of promastigotes cultures as nitrite, a stable by-product derived from NO·. We have previously described the expression of a constitutive nitric oxide synthase (cNOS) in L. amazonensis promastigotes and axenic amastigotes. Comparing those results with the present work, using immunofluorescence assay, it was shown that both L. braziliensis and L. chagasi also express a cNOS. Immunostaining experiments showed that promastigotes from early passages of these species in culture had a strong immunoreactivity against anti-cNOS and anti-endothelial cell NOS, in comparison with the same parasite cultured for long time, suggesting a correlation between the NO· production and the presence of metacyclic forms prominent in those newly isolated parasites. These data corroborate findings of a higher NO· production by those parasites, following the growth curve. The relationship between the two NO·-generating systems in the parasite and in their host cell warrants further investigation. The presence of cNOS raises the possibility of a similar type of cross-talk or down-regulation between the NO· signaling systems in host cells and the lower eukaryotic-like Leishmania sp.

Chemical and Biological Analyses of the Essential Oils and Main Constituents of Piper Species

The essential oils obtained from leaves of Piper duckei and Piper demeraranum by hydrodistillation were analyzed by gas chromatography-mass spectrometry. The main constituents found in P. demeraranum oil were limonene (19.3%) and β-elemene (33.1%) and in P. duckei oil the major components found were germacrene D (14.7%) and trans-caryophyllene (27.1%). P. demeraranum and P. duckei oils exhibited biological activity, with IC50 values between 15 to 76 μg mL−1 against two Leishmania species, P. duckei oil being the most active. The cytotoxicity of the essential oils on mice peritoneal macrophage cells was insignificant, compared with the toxicity of pentamidine. The main mono- and sesquiterpene, limonene (IC50 = 278 μM) and caryophyllene (IC50 = 96 μM), were tested against the strains of Leishmania amazonensis, and the IC50 values of these compounds were lower than those found for the essential oils of the Piper species. The HET-CAM test was used to evaluate the irritation potential of these oils as topical products, showing that these oils can be used as auxiliary medication in cases of cutaneous leishmaniasis, with less side effects and lower costs.

Recentes avanços da quimioterapia das leishmanioses: moléculas intracelulares como alvo de fármacos

Leishmanioses sao doencas causadas por protozoarios do genero Leishmania sp., que se apresentam na forma promastigota ou amastigota; os promastigotas infectam o inseto vetor e os amastigotas sao as formas infectivas antes presentes em macrofagos humanos. O tratamento utilizado pela clinica tem se mostrado ineficaz; os farmacos utilizados se apresentam na forma injetavel, o que dificulta o tratamento, ja que o paciente, para ser tratado, deve ser internado para as aplicacoes - que sao dolorosas - e assim muitos pacientes desistem do tratamento. Outra razao para a internacao e a monitoracao dos efeitos colaterais causados pelos farmacos. Por estas razoes a quimioterapia para leishmaniose tem sido objeto de estudo de muitos laboratorios de pesquisa, os quais tem testado outras substâncias quimicas e extratos de plantas com a finalidade de se encontrar novos agentes leishmanicidas com menores efeitos colaterais e otima biodisponibilidade. Alem disso, pesquisam-se, tambem, outras formas farmaceuticas que viabilizem a aplicacao desses farmacos, o que tornaria desnecessaria a internacao do paciente para se efetuar o tratamento. Este artigo visa discutir os recentes avancos da quimioterapia utilizada para as leishmanioses e, tambem, apresentar os aspectos farmacologicos e bioquimicos da participacao de moleculas intracelulares do parasita como alvos de farmacos.