Histamine H1-receptor antagonists against leishmania (L. ) infantum: an in vitro and in vivo evaluation using phosphatidylserine-liposomes

Considering the limited and toxic therapeutic arsenal available for visceral leishmaniasis (VL), the drug repositioning approach could represent a promising tool to the introduction of alternative therapies. Histamine H1-receptor antagonists are drugs belonging to different therapeutic classes, including antiallergics and anxyolitics. In this work, we described for the first time the activity of H1-antagonists against L. (L.) infantum and their potential effectiveness in an experimental hamster model. The evaluation against promastigotes demonstrated that chlorpheniramine, cinnarizine, hydroxyzine, ketotifen, loratadine, quetiapine and risperidone exerted a leishmanicidal effect against promastigotes, with IC50 values in the range of 13-84µM. The antihistaminic drug cinnarizine demonstrated effectiveness against the intracellular amastigotes, with an IC50 value of 21µM. The mammalian cytotoxicity was investigated in NCTC cells, resulting in IC50 values in the range of 57-229µM. Cinnarizine was in vivo studied as a free formulation and entrapped into phosphatidylserine-liposomes. The free drug was administered for eight consecutive days at 50mg/kg by intraperitoneal route (i.p.) and at 100mg/kg by oral route to L. infantum-infected hamsters, but showed lack of effectiveness in both regimens, as detected by real time PCR. The liposomal formulation was administered by i.p. route at 3mg/kg for eight days and reduced the parasite burden to 54% in liver when compared to untreated group; no improvement was observed in the spleen of infected hamsters. Cinnarizine is the first antihistaminic drug with antileishmanial activity and could be used as scaffold for drug design studies for VL.

The potential of secondary metabolites from plants as drugs or leads against protozoan neglected diseases - part II.

Infections with protozoan parasites are a major cause of disease and mortality in many tropical countries of the world. Diseases caused by species of the genera Trypanosoma (Human African Trypanosomiasis and Chagas Disease) and Leishmania (various forms of Leishmaniasis) are among the seventeen "Neglected Tropical Diseases" (NTDs) defined by the WHO. Furthermore, malaria (caused by various Plasmodium species) can be considered a neglected disease in certain countries and with regard to availability and affordability of the antimalarials. Living organisms, especially plants, provide an innumerable number of molecules with potential for the treatment of many serious diseases. The current review attempts to give an overview on the potential of such plant-derived natural products as antiprotozoal leads and/or drugs in the fight against NTDs. In part I, a general description of the diseases, the current state of therapy and need for new therapeuticals, assay methods and strategies applied in the search for new plant derived natural products against these diseases and an overview on natural products of terpenoid origin with antiprotozoal potential were given. The present part II compiles the current knowledge on natural products with antiprotozoal activity that are derived from the shikimate pathway (lignans, coumarins, caffeic acid derivatives), quinones of various structural classes, compounds formed via the polyketide pathways (flavonoids and related compounds, chromenes and related benzopyrans and benzofurans, xanthones, acetogenins from Annonaceae and polyacetylenes) as well as the diverse classes of alkaloids. In total, both parts compile the literature on almost 900 different plant-derived natural products and their activity data, taken from over 800 references. These data, as the result of enormous efforts of numerous research groups world-wide, illustrate that plant secondary metabolites represent an immensely rich source of chemical diversity with an extremely high potential to yield a wealth of lead structures towards new therapies for NTDs. Only a small percentage, however, of the roughly 200,000 plant species on earth have been studied chemically and only a small percentage of these plants or their constituents has been investigated for antiprotozoal activity. The repository of plant-derived natural products hence deserves to be investigated even more intensely than it has been up to present.

The potential of secondary metabolites from plants as drugs or leads against protozoan neglected diseases - part I.

Infections with protozoan parasites are a major cause of disease and mortality in many tropical countries of the world. Diseases caused by species of the genera Trypanosoma (Human African Trypanosomiasis and Chagas Disease) and Leishmania (various forms of Leishmaniasis) are among the seventeen "Neglected Tropical Diseases" (NTDs) defined as such by WHO due to the neglect of financial investment into research and development of new drugs by a large part of pharmaceutical industry and neglect of public awareness in high income countries. Another major tropical protozoan disease is malaria (caused by various Plasmodium species), which -although not mentioned currently by the WHO as a neglected disease- still represents a major problem, especially to people living under poor circumstances in tropical countries. Malaria causes by far the highest number of deaths of all protozoan infections and is often (as in this review) included in the NTDs. The mentioned diseases threaten many millions of lives world-wide and they are mostly associated with poor socioeconomic and hygienic environment. Existing therapies suffer from various shortcomings, namely, a high degree of toxicity and unwanted effects, lack of availability and/or problematic application under the life conditions of affected populations. Development of new, safe and affordable drugs is therefore an urgent need. Nature has provided an innumerable number of drugs for the treatment of many serious diseases. Among the natural sources for new bioactive chemicals, plants are still predominant. Their secondary metabolism yields an immeasurable wealth of chemical structures which has been and will continue to be a source of new drugs, directly in their native form and after optimization by synthetic medicinal chemistry. The current review, published in two parts, attempts to give an overview on the potential of such plant-derived natural products as antiprotozoal leads and/or drugs in the fight against NTDs.

The potential of secondary metabolites from plants as drugs or leads against protozoan neglected diseases - part I

Infections with protozoan parasites are a major cause of disease and mortality in many tropical countries of the world. Diseases caused by species of the genera Trypanosoma (Human African Trypanosomiasis and Chagas Disease) and Leishmania (various forms of Leishmaniasis) are among the seventeen "Neglected Tropical Diseases" (NTDs) defined as such by WHO due to the neglect of financial investment into research and development of new drugs by a large part of pharmaceutical industry and neglect of public awareness in high income countries. Another major tropical protozoan disease is malaria (caused by various Plasmodium species), which -although not mentioned currently by the WHO as a neglected disease- still represents a major problem, especially to people living under poor circumstances in tropical countries. Malaria causes by far the highest number of deaths of all protozoan infections and is often (as in this review) included in the NTDs. The mentioned diseases threaten many millions of lives world-wide and they are mostly associated with poor socioeconomic and hygienic environment. Existing therapies suffer from various shortcomings, namely, a high degree of toxicity and unwanted effects, lack of availability and/or problematic application under the life conditions of affected populations. Development of new, safe and affordable drugs is therefore an urgent need. Nature has provided an innumerable number of drugs for the treatment of many serious diseases. Among the natural sources for new bioactive chemicals, plants are still predominant. Their secondary metabolism yields an immeasurable wealth of chemical structures which has been and will continue to be a source of new drugs, directly in their native form and after optimization by synthetic medicinal chemistry. The current review, published in two parts, attempts to give an overview on the potential of such plant-derived natural products as antiprotozoal leads and/or drugs in the fight against NTDs.

Antiprotozoal activity of Brazilian plant extracts from isoquinoline alkaloid-producing families.

Leishmaniasis and Chagas disease afflict the poorest countries in the world. The Brazilian flora represents a rich source for the screening of potential antiparasitic compounds. In this work, we tested the total alkaloid and ethanol extracts of nine different plants from Brazilian families which produce isoquinoline alkaloids, to determine their in vitro antiparasitic effect against L. chagasi and T. cruzi parasites. Promastigotes of L. chagasi were shown to be susceptible only to the total alkaloid extracts of A. crassiflora (EC50 value = 24.89 microg/ml), A. coriacea (EC50 value = 41.60 microg/ml), C. ovalifolia (EC50 value = 63.88 microg/ml) and G. australis (EC50 value = 37.88 microg/ml). Except for the G. australis total alkaloids, all the three extracts presented a considerable activity when tested against intracellular amastigotes. The most effective alkaloid extracts were those from A. crassiflora and C. ovalifolia, which reduced the number of infected macrophages at 25 microg/ml by 86.1% and 89.8%, respectively. Among the 18 tested extracts, 16 showed anti-Trypanosoma activity. Eight extracts (A. crassiflora, A. coriacea, C. ovalifolia, D. furfuracea, D. lanceolata, S. guianensis, X. emarginata and G. australis) were the most effective against the trypomastigotes, killing approximately 100% of the parasites at the maximal concentration of 100 microg/ml. Cytotoxicity against mammalian cells was evaluated for all extracts, but potential ones showed little or no cytotoxicity and a considerable antiparasitic effect, including D. furfuracea, D. lanceolata, G. australis, S. guianensis and X. emarginata. Plants are a rich source of natural compounds, and a powerful tool for the development of new arsenals for the therapy of protozoan diseases.

Bothrops moojeni venom kills Leishmania spp. with hydrogen peroxide generated by its L-amino acid oxidase.

Leishmaniasis is an endemic tropical disease in South America, with few therapeutic approaches. Snake venoms are complex protein mixtures with biological actions that could be used as tools for drug development. Here we show that Bothrops moojeni crude venom presented a killing effect in vitro against Leishmania spp. promastigotes, but not with amastigotes, as determined by a viability assay using the mitochondrial oxidative function. Purification of active fractions from crude venom was performed by molecular exclusion and ion exchange chromatography. Anti-Leishmania and l-amino acid oxidase (L-AAO, EC.1.4.3.2.) activities co-eluted in the same fractions. The molecular weight of the active enzyme was estimated to be 140 kDa by molecular exclusion chromatography, and 69 kDa by SDS--PAGE, with a 4.8 isoelectric point. Using substrate subtraction and catalase for scavenging, the action of L-AAO was demonstrated to be hydrogen-peroxide-dependent.