The efficacy of 2-nitrovinylfuran derivatives against Leishmania in vitro and in vivo

Despite recent advances in the treatment of some forms of leishmaniasis, the available drugs are still far from ideal due to inefficacy, parasite resistance, toxicity and cost. The wide-spectrum antimicrobial activity of 2-nitrovinylfuran compounds has been described, as has their activity against Trichomonas vaginalis and other protozoa. Thus, the aim of this study was to test the antileishmanial activities of six 2-nitrovinylfurans in vitro and in a murine model of leishmaniasis. Minimum parasiticide concentration (MPC) and 50% inhibitory concentration (IC₅₀) values for these compounds against the promastigotes of Leishmania amazonensis, Leishmania infantum and Leishmania braziliensis were determined, as were the efficacies of two selected compounds in an experimental model of cutaneous leishmaniasis (CL) caused by L. amazonensis in BALB/c mice. All of the compounds were active against the promastigotes of the three Leishmania species tested. IC₅₀ and MPC values were in the ranges of 0.8-4.7 µM and 1.7-32 µM, respectively. The compounds 2-bromo-5-(2-bromo-2-nitrovinyl)-furan (furvina) and 2-bromo-5-(2-methyl-2-nitrovinyl)-furan (UC245) also reduced lesion growth in vivo at a magnitude comparable to or higher than that achieved by amphotericin B treatment. The results demonstrate the potential of this class of compounds as antileishmanial agents and support the clinical testing of Dermofural^(r) (a furvina-containing antifungal ointment) for the treatment of CL.     

Therapeutic switching: from antidermatophytic essential oils to new leishmanicidal products

This study examined whether the antidermatophytic activity of essential oils (EOs) can be used as an indicator for the discovery of active natural products against Leishmania amazonensis. The aerial parts of seven plants were hydrodistilled. Using broth microdilution techniques, the obtained EOs were tested against three strains of dermatophytes (Trichophyton mentagrophytes, Microsporum gypseum and Microsporum canis). To compare the EOs antifungal and antiparasitic effects, the EOs activities against axenic amastigotes of L. amazonensis were concurrently evaluated. For the most promising EOs, their antileishmanial activities against parasites infecting peritoneal macrophages of BALB/c mice were measured. The most interesting antifungal candidates were the EOs from Cymbopogon citratus, Otacanthus azureus and Protium heptaphyllum, whereas O. azureus, Piper hispidum and P. heptaphyllum EOs exhibited the lowest 50% inhibitory concentration (IC₅₀) values against axenic amastigotes, thus revealing a certain correspondence between both activities. The P. hispidum EO was identified as the most promising product in the results from the infected macrophages model (IC₅₀: 4.7 µg/mL, safety index: 8). The most abundant compounds found in this EO were sesquiterpenes, notably curzerene and furanodiene. Eventually, the evaluation of the antidermatophytic activity of EOs appears to be an efficient method for identifying new potential drugs for the treatment of L. amazonensis.     

Crude ethanolic extract, lignoid fraction and yangambin from Ocotea duckei (Lauraceae) show antileishmanial activity

Crude ethanolic extract, lignoid fraction and the purified compound yangambin were obtained from Ocotea duckei (Lauraceae) and their antileishmanial activity was tested against promastigote forms of Leishmania chagasi and Leishmania amazonensis cultivated in Schneider medium, supplemented with 20% of fetal bovine serum. All substances presented antileishmanial activity with IC50 values of 135.7 microg/mL for the crude ethanolic extract, 26.5 microg/mL for the lignoid fraction and 49.0 microg/mL for yangambin on L. chagasi. For L. amazonensis the IC50 values were 143.7 microg/mL, 48.2 microg/mL and 64.9 microg/mL for the crude ethanolic extract, the lignoid fraction, and the purified compound yangambin, respectively. The crude ethanolic extract, lignoid fraction, and yangambin caused an inhibition higher than Glucantime, a reference drug used for the treatment of leishmaniasis.     

Evaluation of antileishmanial activity of eupomatenoid-5, a compound isolated from leaves of Piper regnellii var. pallescens

Infection with Leishmania spp. causes a disease with multifaceted clinical manifestations in humans. The treatment for leishmaniasis is dependent on a limited range of drugs. Here we investigated the antileishmanial activity of eupomatenoid-5, a neolignan isolated from leaves of Piper regnellii var. pallescens. We showed that eupomatenoid-5 had a dose-dependent activity during 72 h of treatment, exhibiting IC₅₀ of 9.0 µg/mL and 13.0 µg/mL for promastigote and axenic amastigote forms, respectively, and IC₅₀ of 5.0 µg/mL for intracellular amastigote forms of Leishmania amazonensis. When L. amazonensis was treated with eupomatenoid-5, it underwent considerable ultrastructural alterations, as shown by transmission electron microscopy. Among the alterations was the appearance of intense exocytic activity in the region of the flagellar pocket, myelin-like figures, and vacuoles in the cytoplasm of parasites treated with 9.0 µg/mL. Cells treated with 25.0 µg/mL showed a very large structure, apparently an extension of the endoplasmic reticulum. Also, mitochondrial swelling was detected at this concentration, indicating damage and significant change in this organelle. A cytotoxicity assay showed that the action of the isolated compound is more specific for protozoa and it is not toxic to macrophages. Our studies indicated that eupomatenoid-5 might be a potential new drug for the treatment of leishmaniasis, because this compound displays interesting antileishmanial activity in vitro against promastigote, axenic amastigote, and intracellular amastigote forms of L. amazonensis.     

Potential of 2-Hydroxy-3-Phenylsulfanylmethyl-[1,4]-Naphthoquinones against Leishmania (L.) infantum: Biological Activity and Structure-Activity Relationships

Naphtoquinones have been used as promising scaffolds for drug design studies against protozoan parasites. Considering the highly toxic and limited therapeutic arsenal, the global negligence with tropical diseases and the elevated prevalence of co-morbidities especially in developing countries, the parasitic diseases caused by various Leishmania species (leishmaniasis) became a significant public health threat in 98 countries. The aim of this work was the evaluation of antileishmanial in vitro potential of thirty-six 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones obtained by a three component reaction of lawsone, the appropriate aldehyde and thiols adequately substituted, exploiting the in situ generation of o-quinonemethides (o-QM) via the Knoevenagel condensation. The antileishmanial activity of the naphthoquinone derivatives was evaluated against promastigotes and intracellular amastigotes of Leishmania (Leishmania) infantum and their cytotoxicity was verified in mammalian cells. Among the thirty-six compounds, twenty-seven were effective against promastigotes, with IC₅₀ values ranging from 8 to 189 µM; fourteen compounds eliminated the intracellular amastigotes, with IC₅₀ values ranging from 12 to 65 µM. The compounds containing the phenyl groups at R₁ and R₂ and with the fluorine substituent at the phenyl ring at R₂, rendered the most promising activity, demonstrating a selectivity index higher than 15 against amastigotes. A QSAR (quantitative structure activity relationship) analysis yielded insights into general structural requirements for activity of most compounds in the series. Considering the in vitro antileishmanial potential of 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones and their structure-activity relationships, novel lead candidates could be exploited in future drug design studies for leishmaniasis.     

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.     

Cynaroside inhibits Leishmania donovani UDP-galactopyranose mutase and induces reactive oxygen species to exert antileishmanial response

Cynaroside, a flavonoid, has been shown to have antibacterial, antifungal and anticancer activities. Here, we evaluated its antileishmanial properties and its mechanism of action through different in silico and in vitro assays. Cynaroside exhibited antileishmanial activity in time- and dose-dependent manner with 50% of inhibitory concentration (IC₅₀) value of 49.49 ± 3.515 µM in vitro. It inhibited the growth of parasite significantly at only 20 µM concentration when used in combination with miltefosine, a standard drug which has very high toxicity. It also inhibited the intra-macrophagic parasite significantly at low doses when used in combination with miltefosine. It showed less toxicity than the existing antileishmanial drug, miltefosine at similar doses. Propidium iodide staining showed that cynaroside inhibited the parasites in G₀/G₁ phase of cell cycle. 2,7-dichloro dihydro fluorescein diacetate (H₂DCFDA) staining showed cynaroside induced antileishmanial activity through reactive oxygen species (ROS) generation in parasites. Molecular-docking studies with key drug targets of Leishmania donovani showed significant inhibition. Out of these targets, cynaroside showed strongest affinity with uridine diphosphate (UDP)-galactopyranose mutase with −10.4 kcal/mol which was further validated by molecular dynamics (MD) simulation. The bioactivity, ADMET (absorption, distribution, metabolism, excretion and toxicity) properties, Organisation for Economic Co-operation and Development (OECD) chemical classification and toxicity risk prediction showed cynaroside as an enzyme inhibitor having sufficient solubility and non-toxic properties. In conclusion, cynaroside may be used alone or in combination with existing drug, miltefosine to control leishmaniasis with less cytotoxicity.     

Synthesis,antileishmanial and antitrypanosomal activities of N-substituted tetrahydro-β-carbolines

A series of N-substituted tetrahydro-β-carbolines were synthesized and screened for antileishmanial activity through an in vitro assay that involves promastigotes and axenic amastigotes of Leishmania donovani, the causative agent for visceral leishmaniasis. The thiophen-2-yl analogs 9b and 11f and naphthyl analog 11h were found to show significant activity against promastigotes with IC₅₀ values of 12.7, 9.1 and 22.1 μM, respectively. Analogs 9b and 11h were also effective against axenic amastigotes with IC₅₀ values of 62.8 and 87.6 μM, respectively. The antileishmanial activity of analogs was then tested in human macrophage cell line infected with L. donovani amastigotes and 2-naphthyl linked analog 11h was found to be effective with IC₅₀ value of 28.3 μM. Several analogs also displayed antitrypanosomal activity against Trypanosoma brucei, the causative agent for human African trypanosomiasis. Compounds 11e, 11f and 11h were more effective than others with IC₅₀ values of 1.0, 8.9 and 10.2 μM, respectively. All synthesized analogs were not cytotoxic towards mammalian cell lines including Vero (monkey kidney fibroblasts), HEPG2 (human hepatoma cells), LLC-PK₁ (pig kidney epithelial cells) and THP-1 (human macrophages).     

Chemical constituents of Mussaenda erythrophylla Schumach. & Thonn. (Rubiaceae) and their chemophenetic significance

The chemical investigation of the CH₂Cl₂/MeOH (1:1) extract from the aerial part of Mussaenda erythrophylla Schumach. & Thonn. (Rubiaceae) resulted in the isolation of sixteen known compounds (1–16) distributed in coumarins, flavonoid glucosides, quinic acid derivatives, triterpenoids, monoglycerid, steroids, tetraterpenoid and polyol. The structures of the compounds were determined by spectrometric and spectroscopic analysis including MS and NMR data followed by their comparison with reported ones in the literature. The chemophenetic significance of the isolated compounds was discussed. The crude extract and some of the isolated compounds were assessed in vitro for their antileishmanial, cytotoxic and antiplasmodial activities. The crude extract of M. erythrophylla showed moderate antileishmanial activity (IC₅₀ = 61.6 μg/mL) while the hexane soluble fraction showed good antileishmanial activity (IC₅₀ = 31.06 μg/mL) compared to the reference drug amphotericin B (IC₅₀ = 0.11 μM). Compounds 11 and 9 also exhibited potent antileishmanial activity (IC₅₀ = 53.7–52.0 μM). The crude extract as well as the ethyl acetate soluble fraction also exhibited good antiplasmodial activity (IC₅₀ = 7.43 ± 0.00 μg/mL and 14.49 ± 2.96 μg/mL respectively), while compounds 11, 15 and 16 showed weak activity with IC₅₀ > 20 μM compared to the reference drug artemisinin (IC₅₀ = 0.014 ± 0.001 μM).     

New series of 3,5-disubstituted tetrahydro-2H-1,3,5-thiadiazine thione (THTT) derivatives: Synthesis and potent antileishmanial activity

Four series of heterocyclic compounds, namely, tetrahydro-2H-1,3,5-thiadiazine thione derivatives were synthesized in good to excellent yields and were screened for their in vitro antileishmanial activities against Leishmania major (promastigotes). Most of the compounds showed significant antileishmanial activity within the range of IC₅₀?=?15.48–39.36?μM when compared with standard pentamidine (IC₅₀?=?14.95?μM). The structure-activity relationship showed that N-3 and N-5 substituents have a key role against leishmanicidal activity. The ester analogues (series B) were found to have a 1.5 to 5-fold reduced activity compared to their acidic counterparts. Cytotoxicity against mammalian mouse fibroblast 3?T3 cells was also evaluated and compared between the acid and its ester analogue. The reduction of antileishmanial activity and loss of toxicity in the newly developed THTT ester derivative indicates that these compounds can be used as a template study for the production of effective antileishmanial ester prodrugs.     

In vitro antileishmanial activity and cytotoxicity of essential oil from Lippia sidoides Cham

Leishmaniasis is a widespread tropical infection caused by different species of Leishmania protozoa. There is no vaccine available for Leishmania infections and conventional treatments are very toxic to the patients. Therefore, antileishmanial drugs are urgently needed. In this study we have analyzed the effects of essential oils from Lippia sidoides (LSEO) and its major compound thymol on the growth, viability and ultrastructure of Leishmania amazonensis. The essential oil and thymol showed significant activity against promastigote forms of L. amazonensis, with IC₅₀/48 h of 44.38 and 19.47 μg/mL respectively. However, thymol showed toxicity against peritoneal macrophages and low selectivity against the promastigotes when compared with the crude LSEO. On the other hand, no cytotoxic effect was observed in macrophages treated with the crude essential oil. Incubation of L. amazonensis-infected macrophages with LSEO showed a marked reduction in amastigote survival within the macrophages. Significant morphological alterations as accumulation of large lipid droplets in the cytoplasm, disrupted membrane and wrinkled cells were usually seen in treated parasites. The LSEO's activity against both promastigote and the amstigote forms of L. amazonensis, together with its low toxicity to mammalian cells, point to LSEO as a promising agent for the treatment of cutaneous leishmaniasis.     

Antimicrobial and cytotoxicity activities of the medicinal plant Primula macrophylla

Primula macrophylla (Primulaceae) is reported as to be useful in asthma, restlessness, insomnia and fish poisoning. Antifungal and toxic activities of crude extract, fractions and a pure isolated compound exhibited statistically significant activities. Excellent antifungal activity was found in the crude extract, benzene and ethyl acetate fractions against T. longifusis and against M. canis with different MIC values. Antileishmanial activity (IC₅₀ = 50ug/mL) was observed as compared to standard drug Amphotericin B, and cytotoxic activity (LD₅₀ = 47.919μg/mL) was also found in the chloroform fraction. While pure compound 2-phenylchromone (Flavone) isolated from the chloroform fraction showed good activity (IC₅₀ = 25μg/mL) against Leishmania and cytotoxicity (LD₅₀ = 2.0116 μg/mL) in Brine Shrimp experiments. From antileishmanial and cytotoxic activity it can be concluded that 2-phenylchromone is the major compound responsible for these activities.     

Phytochemical,Antiplasmodial, Cytotoxic and Antimicrobial Evaluation of a Southeast Brazilian Brown Propolis Produced by Apis mellifera Bees

Seven phenolic compounds (ferulic acid, caffeic acid, 4-methoxycinnamic acid, 3,4-dimethoxycinnamic acid, 3-hydroxy-4-methoxybenzaldehyde, 3-methoxy-4-hydroxypropiophenone and 1-O,2-O-digalloyl-6-O-trans-p-coumaroyl-β-D-glucopyranoside), a flavanonol (7-O-methylaromadendrin), two lignans (pinoresinol and matairesinol) and six diterpenic acids/alcohol (19-acetoxy-13-hydroxyabda-8(17),14-diene, totarol, 7-oxodehydroabietic acid, dehydroabietic acid, communic acid and isopimaric acid) were isolated from the hydroalcoholic extract of a Brazilian Brown Propolis and characterized by NMR spectral data analysis. The volatile fraction of brown propolis was characterized by CG-MS, composed mainly of monoterpenes and sesquiterpenes, being the major α-pinene (18.4 %) and β-pinene (10.3 %). This propolis chemical profile indicates that Pinus spp., Eucalyptus spp. and Araucaria angustifolia might be its primary plants source. The brown propolis displayed significant activity against Plasmodium falciparum D6 and W2 strains with IC₅₀ of 5.3 and 9.7 μg/mL, respectively. The volatile fraction was also active with IC₅₀ of 22.5 and 41.8 μg/mL, respectively. Among the compounds, 1-O,2-O-digalloyl-6-O-trans-p-coumaroyl-β-D-glucopyranoside showed IC₅₀ of 3.1 and 1.0 μg/mL against D6 and W2 strains, respectively, while communic acid showed an IC₅₀ of 4.0 μg/mL against W2 strain. Cytotoxicity was determined on four tumor cell lines (SK-MEL, KB, BT-549, and SK-OV-3) and two normal renal cell lines (LLC-PK1 and VERO). Matairesinol, 7-O-methylaromadendrin, and isopimaric acid showed an IC₅₀ range of 1.8–0.78 μg/mL, 7.3–100 μg/mL, and 17–18 μg/mL, respectively, against the tumor cell lines but they were not cytotoxic against normal cell lines. The crude extract of brown propolis displayed antimicrobial activity against C. neoformans, methicillin-resistant Staphylococcus aureus, and P. aeruginosa at 29.9 μg/mL, 178.9 μg/mL, and 160.7 μg/mL, respectively. The volatile fraction inhibited the growth of C. neoformans at 53.0 μg/mL. The compounds 3-hydroxy-4-methoxybenzaldehyde, 3-methoxy-4-hydroxypropiophenone and 7-oxodehydroabietic acid were active against C. neoformans, and caffeic and communic acids were active against methicillin-resistant Staphylococcus aureus.     

Tamoxifen Induces Apoptosis of Leishmania major Promastigotes in Vitro

Tamoxifen is an antagonist of the estrogen receptor and currently used for the treatment of breast cancer. The current treatment of cutaneous leishmaniasis with pentavalent antimony compounds is not satisfactory. Therefore, in this study, due to its antileishmanial activity, effects of tamoxifen on the growth of promastigotes and amastigotes of Leishmania major Iranian strain were evaluated in vitro. Promastigotes and amastigotes were treated with different concentrations (1, 5, 10, 20, and 50 μg/ml) and time periods (24, 48, and 72 hr) of tamoxifen. After tamoxifen treatment, MTT assay (3-[4,5-dimethylthiazol-2-yl]-2,5 biphenyl tetrazolium bromide assay) was used to determine the percentage of live parasites and Graph Pad Prism software to calculate IC₅₀. Flow cytometry was applied to investigate the induction of tamoxifen-induced apoptosis in promastigotes. The half maximal inhibitory concentration (IC₅₀) of tamoxifen on promastigotes was 2.6 μg/ml after 24 hr treatment. Flow cytometry analysis showed that tamoxifen induced early and late apoptosis in Leishmania promastigotes. While after 48 hr in control group the apoptosis was 2.0%, the 50 µg/L concentration of tamoxifen increased it to 59.7%. Based on the in vitro antileishmanial effect, tamoxifen might be used for leishmaniasis treatment; however, further researches on in vivo effects of tamoxifen in animal models are needed.     

Effect of thiadiazine derivatives on intracellular amastigotes of Leishmania amazonensis

Current therapy for leishmaniasis is not satisfactory. We describe the in vitro antiproliferative effects of new thiadiazine derivatives against Leishmania amazonensis. The compounds were found to be active against the amastigote form of the parasite, inhibiting parasite growing, from 10 to 89%, at a concentration of 100 ng/ml. This activity suggests that thiadiazine derivatives could be considered as potential antileishmanial compounds.     

Antileishmanial activity of indole alkaloids from Aspidosperma ramiflorum

The present study was designated to evaluate the antileishmanial activity of acid and basic fractions that were obtained after acid-basic extraction, from ethanolic 70% crude extract and pure compounds from the stem bark of Aspidosperma ramiflorum. The basic alkaloidal fraction presented a good activity against the extracellular form (promastigotes) of Leishmania (L.) amazonensis (LD(50) value<47 microg/ml). Based on these findings, the basic fraction was fractionated on silica gel column chromatography in a bioassay-guided fractionation affording individual purified ramiflorines A and B. Both ramiflorines A and B showed significant activity against Leishmania (L.) amazonensis (LD(50) values of 16.3+/-1.6 microg/ml and 4.9+/-0.9 microg/ml, respectively). Our results are promising, showing that these compounds are biologically active against Gram-positive bacteria.     

Nigrosphaerin A a new isochromene derivative from the endophytic fungus Nigrospora sphaerica

Nigrosphaerin A, a new isochromene derivative (1), was isolated from the endophytic fungus Nigrospora sphaerica and chemically identified as 3-(3,4-dihydroxyphenyl)-4,6,8-trihydroxy-1H-isochromen-1-one-6-O-β-d-glucopyranoside. In addition nineteen known compounds (2–20) were isolated from the same fungus and chemically identified. Compounds (1–3, 5, and 7–16) were isolated for the first time from this fungus. In vitro antileukemic, antileishmanial, antifungal, antibacterial and antimalarial activities of (1–20) were examined. Compounds 5, 7, 9 and 10 showed good antileukemic activity against HL60 cells with IC₅₀ values of 0.03, 0.39, 0.2 and 0.4 μg/mL, respectively and against K562 cells with IC₅₀ values of 0.35, 0.35, 0.49 and 0.01 μg/mL, respectively. Compounds 3, 4 and 6 showed moderate antileishmanial activity with IC₅₀ values of 30.2, 26.4 and 36.4 μg/ml, respectively. Compound 7 showed moderate antifungal activity against Cryptococcus neoformans with IC₅₀ value of 14.8 μg/mL.     

In vitro activity of nicotinamide/antileishmanial drug combinations

To improve the management of leishmaniasis, new drugs and/or alternative therapeutic strategies are required. Combination therapy of antileishmanial drugs is currently considered as one of the most rational approaches to lower treatment failure rate and limit drug resistance spreading. Nicotinamide (NAm), also known as vitamin B3 that is already is used in human therapy, exerts in vitro antileishmanial activity. Drug combination studies, performed on L. infantum axenic amastigotes, revealed that NAm significantly improves the antileishmanial activity of trivalent antimony in a synergistic manner while it shows additive activity with amphotericin B and slightly antagonizes pentamidine activity. NAm also significantly increases the toxicity of pentavalent antimony against the intracellular forms of L. infantum, L. amazonensis and L. braziliensis. The potential of NAm to be used as adjuvant during leishmaniasis chemotherapy is further discussed.     

In vitro activity of the hydroethanolic extract and biflavonoids isolated from Selaginella sellowii on Leishmania (Leishmania) amazonensis

This study is the first phytochemical investigation of Selaginella sellowii and demonstrates the antileishmanial activity of the hydroethanolic extract from this plant (SSHE), as well as of the biflavonoids amentoflavone and robustaflavone, isolated from this species. The effects of these substances were evaluated on intracellular amastigotes of Leishmania (Leishmania) amazonensis, an aetiological agent of American cutaneous leishmaniasis. SSHE was highly active against intracellular amastigotes [the half maximum inhibitory concentration (IC50) = 20.2 µg/mL]. Fractionation of the extract led to the isolation of the two bioflavonoids with the highest activity: amentoflavone, which was about 200 times more active (IC50 = 0.1 μg/mL) and less cytotoxic than SSHE (IC50 = 2.2 and 3 μg/mL, respectively on NIH/3T3 and J774.A1 cells), with a high selectivity index (SI) (22 and 30), robustaflavone, which was also active against L. amazonensis (IC50 = 2.8 µg/mL), but more cytotoxic, with IC50 = 25.5 µg/mL (SI = 9.1) on NIH/3T3 cells and IC50 = 3.1 µg/mL (SI = 1.1) on J774.A1 cells. The production of nitric oxide (NO) was lower in cells treated with amentoflavone (suggesting that NO does not contribute to the leishmanicidal mechanism in this case), while NO release was higher after treatment with robustaflavone. S. sellowii may be a potential source of biflavonoids that could provide promising compounds for the treatment of cutaneous leishmaniasis.     

Antileishmanial activity of isolated triterpenoids from Pourouma guianensis.

The inhibiting activity of triterpenoids isolated from the methanolic extract of Pourouma guianensis (Moraceae) leaves is described for promastigotes and intracellular amastigotes of Leishmania amazonensis. Whereas the fractions containing apigenin, friedelin, epi-friedelinol, arjunolic acid, hyptatic acid B, stigmasterol and sitosterol were of no or relatively low inhibitory activity, fractions containing tormentic acid, 2alpha,3beta-dihydroxyursan-12-en-28-oic acid, 2alpha,3beta-dihydroxyolean-12-en-28-oic acid, oleanolic acid and ursolic acid were very potent in inhibiting promastigote growth at 100 microg/ml. Of the eleven isolated compounds, however, only ursolic acid and oleanolic acid showed high activity against intracellular amastigotes (IC50 value = 27 microg/ml and 11 microg/ml, respectively), which was superior to the control drug Glucantime (IC50 value = 83 microg/ml). The antileishmanial activity of oleanolic acid was directed against the parasite and not due to activation of nitric oxide intermediates by macrophages, but this triterpenoid also significantly inhibited the phagocytic capacity of those cells at concentrations above 40 microg/ml, indicating a cytotoxic effect. These results indicate that Pourouma guianensis contains many triterpenoids and some, such as ursolic and oleanolic acids, may serve as lead compounds for new antileishmanial drugs, but chemical modifications may be necessary to avoid unselective cytotoxicity.