Synthesis and biological evaluation of substituted quinolines: potential treatment of protozoal and retroviral co-infections

We report the synthesis of substituted quinolines and their in vitro biological evaluation against the causal agents of cutaneous leishmaniasis, visceral leishmaniasis, African trypanosomiasis and Chagas' disease. Furthermore, several quinolines have also been tested for their anti-retroviral activity in HIV-1 infected cells. The structure-activity relationships of these new synthetic compounds are discussed and emphasis was placed on the treatment of leishmania/HIV co-infections.

2-substituted quinoline alkaloids as potential antileishmanial drugs

Ten 2-substituted quinoline alkaloids isolated from a plant used for treatment of New World cutaneous leishmaniasis have antileishmanial in vitro activities against the extracellular forms of Leishmania spp. BALB/c mice infected with Leishmania amazonensis PH8 or H-142 or Leishmania venezuelensis were treated 1 day after the parasitic infection with a quinoline alkaloid (100 mg/kg of body weight per day) or with reference drug N-methylglucamine antimonate (Glucantime) (56 mg of pentavalent antimony [Sbv] per kg per day) for 14 days. Lesion development was the criterium used to assess disease severity. Two three-carbon chain quinolines [2-n-propylquinoline and 2-(1',2'-trans-epoxypropyl)quinoline (chimanine D)] were more potent than N-methylglucamine antimonate against L. amazonensis PH8, and five quinoline alkaloids [2-(3,4-methylenedioxyphenylethyl)quinoline, cusparine, 2-(3,4-dimethoxyphenylethyl)quinoline, 2-(E)-prop-1'-enylquinoline (chimanine B), and skimmianine] were as effective as the reference drug. Single treatment near the site of infection, 14 days after infection with L. amazonensis, with 2-n-propylquinoline or chimanine B reduced the severity of lesions but less notably than N-methylglucamine antimonate. 2-n-Propylquinoline exhibited significant activity against the virulent strain L. venezuelensis. The active products did not show any apparent toxicities during the experiment. This study is, to our knowledge, the first to show the activity of 2-substituted quinoline alkaloids for experimental treatment of New World cutaneous leishmaniasis. Further investigations of these compounds might yet prove helpful for the development of new antileishmanial drugs.

Natural products as trypanocidal, antileishmanial and antimalarial drugs

Parasitic diseases caused by protozoa as Leishmania, Trypanosome or Plasmodium are responsible for more than three millions deaths annually throughout the developing countries. This review covers recent studies on plant-secondary metabolites isolated from medicinal plants and that have demonstrated moderate to high activity in in vitro and in vivo bioassays against these protozoa. The biological activity of the last promising antiparasitic leads are described.

In vivo efficacy of oral and intralesional administration of 2-substituted quinolines in experimental treatment of new world cutaneous leishmaniasis caused by Leishmania amazonensis

The antileishmanial efficacies of 2-n-propylquinoline, chimanines B and D, 2-n-pentylquinoline, 2-phenylquinoline, 2-(3,4-methylenedioxyphenylethyl) quinoline, and two total alkaloidal extracts of Galipea longiflora were evaluated in BALB/c mice infected with Leishmania amazonensis or Leishmania venezuelensis. Animals were treated for 4 to 6 weeks postinfection with a quinoline by the oral route at 50 mg/kg of body weight twice daily for 15 days or by five intralesional injections at intervals of 4 days with a quinoline at 50 mg/kg of body weight. The reference drug, N-methylglucamine antimonate (Glucantime), was administered by subcutaneous or intralesional injection (regimens of 14, 28, or 56 mg of pentavalent antimony [Sbv] per kg of body weight daily). Twice-daily oral treatment with chimanine B at 50 mg/kg resulted in a decrease in lesion weight by 70% (P < 0.001) and a decrease in the parasite loads by 95% (P < 0.001). Five injections of chimanine B at intervals of 4 days reduced the lesion weight by 74% and the parasite loads in the lesion by 90% compared with the values for the group of untreated mice. Subcutaneous administration of N-methylglucamine antimonate at 28 mg of Sbv kg per day for 15 days reduced the parasite burden by 95% (P < 0.001), and five intralesional injections at the same concentration reduced the parasite burden by 96% (P < 0.001). Other 2-substituted quinolines, 2-n-propylquinoline administered by the oral and intralesional routes, 2-phenylquinoline administered by the oral route, 2-n-pentylquinoline administered by intralesional injection, and two total alkaloidal extracts of G. longiflora administered by the oral route, had intermediate effects. These findings suggest that chimanine B may be chosen as a lead molecule in the development of oral therapy against leishmaniasis.

Biological evaluation of substituted quinolines

Several quinolines were synthesized and evaluated in vitro against several parasites (Trypanosoma brucei, T. cruzi, Leishmania infantum, L. amazonensis, Plasmodium falciparum). Then, they were evaluated in vitro (at 10 microM), against HTLV-1 transformed cells. A few of them displayed interesting activities, comparable to the reference drugs.

Antileishmanial and trypanocidal activity of Brazilian Cerrado plants

The side effects and the emerging resistance to the available drugs against leishmaniasis and trypanosomiasis led to the urgent need for new therapeutic agents against these diseases. Thirty one extracts of thirteen medicinal plants from the Brazilian Cerrado were therefore evaluated in vitro for their antiprotozoal activity against promastigotes of Leishmania donovani, and amastigotes of Trypanosoma cruzi. Among the selected plants, Casearia sylvestris var. lingua was the most active against both L. donovani and T. cruzi. Fifteen extracts were active against promastigotes of L. donovani with concentrations inhibiting 50% of parasite growth (IC50) between 0.1-10 microg/ml, particularly those of Annona crassiflora (Annonaceae), Himatanthus obovatus (Apocynaceae), Guarea kunthiana (Meliaceae), Cupania vernalis (Sapindaceae), and Serjania lethalis (Sapindaceae). With regard to amastigotes of T. cruzi, extracts of A. crassiflora, Duguetia furfuracea (Annonaceae), and C. sylvestris var. lingua were active with IC50 values between 0.3-10 microg/ml. Bioassay fractionations of the more active extracts are under progress to identify the active antiparasite compounds.

Leishmanicidal and trypanocidal activities of Bolivian medicinal plants

Cutaneous and mucocutaneous leishmaniasis are endemic diseases in South America, especially in the subandean areas of the humid lowlands of Bolivia. Fourteen plants used topically in folk medicine to treat cutaneous leishmaniasis were collected in the tropical regions of colonization and in the rain forest occupied by Chimane Indians. Three of four plants used by the Chimane Indians exhibited an in vitro activity against three species of Leishmania. Two of ten plants used by the colonists showed an in vitro activity. We have also included results obtained with extracts from 53 Bolivian medicinal plants used for other diseases and from 43 plants collected with basis of chemotaxonomic criteria from all parts of Bolivia. All extracts were also screened in vitro against three strains of Trypanosoma cruzi (Trypanosomatidae), the causative agent of Chagas' disease.

Substituted quinolines induce inhibition of proliferation of HTLV-1 infected cells

Several quinolines were synthesized and evaluated against HTLV-1 infected cells. Some of them were able to inhibit HTLV-1 cell-growth at 10 microM. Some structure-activity relationships were observed.

Antileishmanial activity of furoquinolines and coumarins from Helietta apiculata

The bark infusion of H. apiculata are used to treat wound healing related to cutaneous leishmaniasis and as anti-inflammatory.

AIM OF THE STUDY

To isolate, purify active constituents of H. apiculata stem bark, and evaluate their in vitro and in vivo antileishmanial activities.

MATERIALS AND METHODS

Isolation by chromatographic methods and chemical identification of furoquinoline alkaloids and coumarins, then evaluation of the in vitro leishmanicidal activity of these compounds against three strains of Leishmania sp. promastigotes and in vivo against Leishmania amazonensis in Balb/c mice.

RESULTS

Furoquinoline alkaloids and coumarins presented a moderate in vitro activity against promastigote forms of Leishmania sp. with IC(50) values in the range between 17 and >50 microg/ml. Balb/c mice infected with Leishmania amazonensis were treated with gamma-fagarine by oral route, or with 3-(1'-dimethylallyl)-decursinol or (-)-heliettin by subscutaneous route for 14 days at 10mg/kg daily. In these conditions, gamma-fagarine, 3-(1'-dimethylallyl)-decursinol and (-)-heliettin showed the same efficacy as the reference drug reducing by 97.4, 95.6 and 98.6% the parasite loads in the lesion, respectively.

CONCLUSION

These compounds showed significant efficacy in L. amazonensis infected mice, providing important knowledge to improve its potential role for a future use in the treatment of cutaneous leishmaniasis.

Efficacy of orally administered 2-substituted quinolines in experimental murine cutaneous and visceral leishmaniases

We report in this study the in vivo efficacy of nine 2-substituted quinolines on the Leishmania amazonensis cutaneous infection murine model and on the Leishmania infantum and Leishmania donovani visceral infection murine models. In the case of the L. amazonensis model, quinolines were administered orally at 25 mg/kg twice daily for 15 days. Quinolines 1, 2, 3, and 7 reduced by 80 to 90% the parasite burdens in the lesion, whereas N-methylglucamine antimoniate (Glucantime), administered by subcutaneous injections at 100 mg [28 mg Sb(V)] per kg of body weight daily, reduced the parasite burdens by 98%. In visceral leishmaniasis due to L. infantum, mice treated orally at 25 mg/kg daily for 10 days with quinolines 1, 4, 5, and 6 showed a significant reduction of parasite burdens in the liver and spleen. These quinolines were significantly more effective than meglumine antimoniate to reduce the parasite burden in both the liver and spleen. Also, the oral in vivo activity of three quinolines (quinolines 4, 5, and 2-n-propylquinoline) were determined against L. donovani (LV 9) at 12.5 and 25 mg/kg for 10 days. Their activity was compared with that of miltefosine at 7.5 mg/kg. Miltefosine, 2-n-propylquinoline, and quinoline 5 at 12.5 mg/kg significantly reduced the parasite burdens in the liver by 72, 66, and 61%, respectively. From the present study, quinoline 5 is the most promising compound against both cutaneous and visceral leishmaniasis. The double antileishmanial and antiviral activities of these compounds suggest that this series could be a potential treatment for coinfection of Leishmania-human immunodeficiency virus.

The activity of 2-substituted quinoline alkaloids in BALB/c mice infected with Leishmania donovani

Potent antileishmanial activity has recently been described in vivo when certain 2-substituted quinoline alkaloids are administered to mice with cutaneous leishmaniasis. We now report the antileishmanial activity of four 2-substituted quinoline alkaloids, namely chimanine D or 2-(1',2'-trans-epoxypropyl) quinoline (I), 2-n-propylquinoline (II), 2-styrylquinoline (III) and 2-(2'-hydroxypropyl) quinoline (IV), for experimental treatment of visceral leishmaniasis in infected BALB/c mice. Subcutaneous treatment with chimanine D for 10 days at 0.54 mmol/kg per day resulted in 86.6% parasite suppression in the liver. Oral administration of 0.54 mmol/kg of 2-n-propylquinoline once daily for 5 or 10 days to L. donovani-infected mice suppressed parasite burdens in liver by 87.8 and 99.9%, respectively. Cutaneous administration of meglumine antimonate for 10 days resulted in 97.4% parasite suppression in the liver. This study is, to our knowledge, the first to demonstrate the activity of 2-substituted quinoline alkaloids in experimental treatment of visceral leishmaniasis. Further biological and chemical studies of these products might yet prove helpful for the development of new antileishmanial drugs.

The effect of some 2-substituted quinolines isolated from Galipea longiflora on Plasmodium vinckei petteri infected mice

We have evaluated the in vivo antiplasmodial activity of six 2-substituted quinolines and a total alkaloidal extract of Galipea longiflora. BALB/c mice infected with Plasmodium vinckei petteri were treated orally at single dose of 50 mg/kg with quinolines or extract. Contrary to the previous results obtained with the Leishmania murine infection, 2-n-pentylquinoline showed activity against P. vinckei petteri. This result seems to confirm the antimalarial efficacy of infused stem bark of G. longiflora.

Effects of canthin-6-one alkaloids from Zanthoxylum chiloperone on Trypanosoma cruzi-infected mice

Canthin-6-one (1), isolated from Zanthoxylum chiloperone (Rutaceae), possesses a broad sprectum of antifungal and leishmanicidal activities. In this study, we have examined the antiparasitic effects of canthin-6-one (1), 5-methoxycanthin-6-one (2), canthin-6-one N-oxide (3), as well as that of the total alkaloids of Zanthoxylum chiloperone stem bark, in Balb/c mice infected either acutely or chronically with Trypanosoma cruzi. The compounds were administered orally or subcutaneously at 5mg/kg/day for 2 weeks, whereas the alkaloidal extract was given at 50mg/kg/day for 2 weeks. The antiparasitic activity was compared with that of benznidazole given at 50mg/kg/day for 2 weeks. In the case of acute infection, parasiteamia was significantly reduced following oral treatment with canthin-6-one (1). Moreover, the total alkaloids of Zanthoxylum chiloperone stem bark led to high levels of parasitological clearance. Seventy days post-infection, the serological response in the acute model was significantly different between oral canthin-6-one (1) and benznidazole-treated mice. Chronic model of the disease showed that both canthin-6-one (1) and the alkaloidal extract at the above dosage induced 80-100% animal survival compared to untreated controls. These results indicate that canthin-6-one (1) exhibits trypanocidal activity in vivo in the mouse model of acute or chronic infection. This is the first demonstration of anti-Trypanosoma cruzi activity for a member of this chemical group (canthinones). Considering the very low toxicity of canthin-6-one (1), our results suggest that long-term oral treatment with this natural product could prove advantageous compared to the current chemotherapy of Chagas disease.

Antifungal compounds from Zanthoxylum chiloperone var. angustifolium

An alkaloidal extract of the stem barks of Zanthoxylum chiloperone var. angustifolium exhibited antifungal activity against Candida albicans, Aspergillus fumigatus and Trichophyton mentagrophytes var. interdigitale using a TLC bioautographic method. Bioassay-guided fractionation of this extract resulted in the isolation of two active compounds identi fi ed as canthin-6-one and 5-methoxycanthin-6-one. Canthin-6-one exhibited a broad spectrum of activities against Aspergillus fumigatus, A. niger, A. terreus, Candida albicans, C. tropicalis, C. glabrata, Cryptococcus neoformans, Geotrichum candidum, Saccharomyces cerevisiae, Trichosporon beigelii, Trichosporon cutaneum and Trichophyton mentagrophytes var. interdigitale with MICs values between 5.3 and 46 micro mol/L. 5-methoxy-canthin-6-one was active against only Trichophyton mentagrophytes var. interdigitale with a MIC value of 12.3 micro mol/L.

Comparative evaluation of pyrethroid insecticide formulations against Triatoma infestans (Klug): residual efficacy on four substrates

We investigated the residual efficacy of four insecticide formulations used in Chagas disease vector control campaigns: cyfluthrin 12.5% suspension concentrace (SC), lambda-cyhalothrin 10% wettable powder (WP), deltamethrin 2.5% SC, and 2.5% WP on four types of circular blocks of wood, straw with mud, straw with mud painted with lime, and mud containing 5% of cement. Three concentrations of these insecticides were tested: the LC90 (previously determined on filter paper), the double of the LC90, and the recommended operational dose. For each bioassay test, 15 third-stage nymphs of Triatoma infestans (Klug) (Hemiptera: Reduviidae) were exposed for 120 h to each treatment at 24 h, 30, 60, 90, and 180 days post-spraying. Mortality rates, moulting history and behaviour were recorded at 24, 48, 72, and 120 h of exposure. Mortality rates were highest during the first 30 days post-spraying. Highest mortality rates (above 50%) were observed for deltamethrin 2.5% SC and lambda-cyhalothrin 10% WP on wood blocks up to three months post-spraying. Mud was the substrate on which treatments showed lowest persistence, with the other two substrates showing intermediate residual efficacy of all treatments. During the first 30 days WP formulations were not as effective as SC flowable formulations but, overall in the longer term, WP gave grater mortality rates of T. infestans nymphs exposed at up to six months post-spraying. Porous surfaces, especially mud, showed most variability presumably due to absorption of the insecticide. In contrast the less porous surfaces (i.e. wood and lime-coated mud) kept mortality rates high for longer post-treatment, irrespective of the insecticide concentration used.

Extraction, hemisynthesis, and synthesis of canthin-6-one analogues. Evaluation of their antifungal activities

Zanthoxylum chiloperone var. angustifolium was investigated. Alkaloids 1-3 from the canthin-6-one series were characterized. Derivatives 7-28 were prepared by hemisynthesis or total synthesis. All compounds were tested for in vitro antifungal activities against five pathogenic fungal strains. Analogues of canthin-6-one did not show better antifungal activities.

Leishmanicidal activity of two canthin-6-one alkaloids, two major constituents of Zanthoxylum chiloperone var. angustifolium

The crude alkaloidal extract of Zanthoxylum chiloperone stem bark exhibited in vitro activity against various strains of Leishmania ssp. at 100 microg/ml. Two active major constituents were isolated and identified as canthin-6-one and 5-methoxycanthin-6-one. The effect of these compounds was also tested in an in vivo assay using BALB/c mice infected with Leishmania amazonensis. The mice were treated for 5 weeks postinfection with these alkaloids by oral (14 days) or intralesional route (4 days) at 10 mg/kg daily. The reference drug, N-methylglucamine antimonate was administered by subcutaneous injections at 100 mg/kg for 10 days. Intralesional administration of canthin-6-one reduced the parasite burden but not significantly when it was compared with the untreated group, while the reference drug reduced by 91% the parasite loads in the lesion.

Antiparasitic activity of some New Caledonian medicinal plants

Twenty-nine extracts of 18 medicinal plants used in New Caledonia by traditional healers to treat inflammation, fever and in cicatrizing remedies were evaluated in vitro against several parasites (Leishmania donovani, Trypanosoma brucei brucei, Trichomonas vaginalis and Caenorhabditis elegans). Among the selected plants, Scaevola balansae and Premna serratifolia L. were the most active against Leishmania donovani with IC(50) values between 5 and 10microg/ml. The almond and aril extracts from Myristica fatua had an IC(50) value of 0.5-5microg/ml against Trypanosoma brucei brucei. Only Scaevola balansae extract presented a weak activity against Trichomonas vaginalis. The almond extract from Myristica fatua presented significant activity against Caenorhabditis elegans (IC(50) value of 6.6+/-1.2microg/ml).

Aryl-2 et alkyl-2 quinoléines nouvelles isolées d'une Rutacée bolivienne: Galipealongiflora

Five new 2-aryl and 2-alkyl quinoline alkaloids were obtained from Galipeallongiflora Krause (Rutaceae). These are 2-phenylquinoline 1, 2-(3′,4′-methylenedioxyphenethyl)quinoline 2, 2-(3′,4′-dimethoxyphenethyl)quinoline 3, 2-(3′,4′-methylenedioxystyryl)-4-methoxyquinoline 4, and 2-(1′,2′-pentenyl)-4-methoxyquinoline 6. They are accompanied by three known 2-substituted quinolines, 2-n-amyl-4-methoxyquinoline 5, 2-(3′4′-methylenedioxyphenethyl)-4-methoxyquinoline 7, and 2-phenyl-4-methoxyquinoline 8, and by two known furo[2,3b]quinoline alkaloids: evolitrine and skimmianine. Keywords: Galipealongiflora, Rutaceae, new quinolines.

Antiprotozoal activity of aporphine alkaloids isolated from Unonopsis buchtienii (Annonaceae)

On a preliminary screening, substantial leishmanicidal activity was observed for the petroleum ether and alkaloidal extracts of the stem bark of Unonopsis buchtienii, the alkaloids and sterols isolated from these were studied. Of the alkaloids, liriodenine exhibited the highest activity against Leishmania major and L donovani (IC100 = 3.12 micrograms/mL). On the other hand, O-methylmoschatoline and the petroleum ether extract without alkaloids showed an interesting in vitro activity against Trypanosoma brucei with an IC100 of 6.25 micrograms/mL. The highest cytotoxic activities were found with the petroleum ether extracts without alkaloids and with all alkaloids isolated (IC50 < 9 micrograms/mL for Vero cell line).

Chemical composition and antimicrobial activity of the essential oils from New Caledonian Citrus macroptera and Citrus hystrix

The essential oils from the leaves of Citrus macroptera and C. hystrix, collected in New Caledonia, have been analyzed by gas chromatography/mass spectrometry (GC/MS) and evaluated for their antimicrobial activity. A total of 35 and 38 constituents were identified, representing 99.1 and 89.0% of the essential oils, respectively. Both essential oils were rich in monoterpenes (96.1 and 87.0%, resp.), with beta-pinene as major component (33.3 and 10.9%, resp.), and poor in limonene (2.4 and 4.7%, resp.). Other main components of C. macroptera oil were alpha-pinene (25.3%), p-cimene (17.6%), (E)-beta-ocimene (6.7%), and sabinene (4.8%). The essential oil of C. hystrix was characterized by high contents of terpinen-4-ol (13.0%), alpha-terpineol (7.6%), 1,8-cineole (6.4%), and citronellol (6.0%). The antimicrobial activity was evaluated against five bacteria and five fungi strains. Both oils were inactive against bacteria. However, the C. macroptera leaf oil exhibited a pronounced activity against Trichophyton mentagrophytes var. interdigitale, with a minimal-inhibitory concentration (MIC) of 12.5 microg/ml.