V. Munoz

A search for natural bioactive compounds in Bolivia through a multidisciplinary approach. Part V. Evaluation of the antimalarial activity of plants used by the Tacana Indians.

Thirty extracts of plants traditionally used by the Chacobos, a native community living in the Amazonian part of Bolivia, were screened in vitro and/or in vivo for antimalarial activity. Two of the four species designated as antimalarial, Geissospermum laeve and Maquira coriacea, displayed rather good activity, corroborating their traditional uses. However, they did show a rather high toxicity in vivo. Among twelve species used to cure symptoms relevant to malaria, five showed good activity: Apuleia leiocarpa, Bauhinia guianensis, Nectandra cuspidata, Sparattanthelium amazonum, Tanaecium jaroba. Two species, Qualea paraensis and Sclerolobium aff. guianense, used to treat scabies, showed interesting antimalarial activity in vivo; three other species (Iryanthera laevis, Prunus amplifolia, Pterocarpus aff. amazonum) used for various medicinal purposes, apparently not related with a Plasmodium infection, also showed antimalarial activity. Finally, one species (Derris amazonica) used as a piscicide displayed good in vitro activity, in the same way as one Annonaceae, Guatteria aff. schomburgkiana, used for construction purposes.

Antiprotozoal activities of Colombian plants

In our search for therapeutical alternatives for antiprotozoal chemotherapy, we collected a selection of 44 plants from western Colombia upon ethnopharmacological and chemotaxonomic considerations. Polar and apolar extracts of these species were examined for antimalarial activity using in vitro tests with two clones of Plasmodium falciparum. Leishmanicidal and trypanocidal activity were determined in vitro using promastigote and amastigote forms of several strains of Leishmania sp. and epimastigotes of Trypanosoma cruzi. Among the selected plants, the 15 following species showed good or very good antiprotozoal activity in vitro: Aspidosperma megalocarpon, Campnosperma panamense, Conobea scoparioides, Guarea polymera, Guarea guidonia, Guatteria amplifolia, Huberodendron patinoi, Hygrophila guianensis, Jacaranda caucana, Marila laxiflora, Otoba novogranatensis, Otoba parviflora, Protium amplium, Swinglea glutinosa and Tabernaemontana obliqua. Cytotoxicity was assessed in U-937 cells and the ratio of cytotoxicity to antiprotozoal activity was determined for the active extracts. Ten extracts from eight species showed selectivity indexes > or = 10. Among the extracts that showed leishmanicidal activity, the methylene chloride extract of leaves from C. scoparioides showed a selectivity index in the same range that the one of the Glucantime control. Several of the active leishmanicidal plants are traditionally used against leishmaniasis by the population of the concerned area.

Medicinal plants uses of the Tacana, an Amazonian Bolivian ethnic group

We present the results of an ethnopharmacological investigation of a Bolivian lowland ethnic group, the Tacana. The Tacana have a long tradition of exchange with highland communities. Though facing rapid acculturation, highlighted by the loss of the Tacana language among the younger generations, the knowledge and uses of medicinal plants are still alive. Of the approximately 450 different plant species collected during this survey, 33% had medicinal uses. We present an overview of the traditional Tacana ethnomedicine and pharmacopoeia.

A search for natural bioactive compounds in Bolivia through a multidisciplinary approach: Part IV. Is a new haem polymerisation inhibition test pertinent for the detection of antimalarial natural products?

The search for new antimalarial agents in plant crude extracts using traditional screening tests is time-consuming and expensive. New in vitro alternative techniques, based on specific metabolic or enzymatic process, have recently been developed to circumvent testing of antimalarial activity in parasite culture. The haem polymerisation inhibition test (HPIA) was proposed as a possible routine in vitro assay for the detection of antimalarial activity in natural products. A total of 178 plant extracts from the Pharmacopeia of the Bolivian ethnia Tacana, were screened for their ability to inhibit the polymerisation of haematin. Five extracts from Aloysia virgata (Ruíz & Pavón) A.L. Jussieu (Verbenaceae), Bixa orellana L. (Bixaceae), Caesalpinia pluviosa D.C. (Caesalpiniaceae), Mascagnia stannea (Griseb) Nied. (Malpighiaceae) and Trichilia pleenea (Adr. Jussieu) (Meliaceae) demonstrated more than 70% inhibition of haematin polymerisation at 2.5 mg/ml. The extracts were also tested for antimalarial activity in culture against F32 strain (chloroquine-sensitive) and D2 strain (chloroquine-resistant) of Plasmodium falciparum and in vivo against P. berghei. The extract from Caesalpinia pluviosa was the only one that showed activity in HPIA and in the classical test in culture. The accuracy and pertinence of HPIA, applied to natural products is discussed.

The search for natural bioactive compounds through a multidisciplinary approach in Bolivia. Part II. Antimalarial activity of some plants used by Mosetene indians.

Forty-six different species collected in the Mosetene ethnia, dwelling in the Andean Piedmont of Bolivia, were screened for antimalarial properties. Thirty-three extracts were screened for antimalarial activity in vitro on Plasmodium falciparum chloroquine resistant strain (Indo), and forty-seven extracts were evaluated in vivo on the rodent malaria P. vinckei petteri 279BY. Only two plants are specifically used in combination by the Mosetene against malaria attack (Hymenachne donacifolia and Tesseria integrifolia), but they did not display any activity in vivo at 1000 mg/kg. The in vivo most active extracts were Swietenia macrophylla bark, Trema micrantha bark and Triplaris americana bark, not all of them were used for antimalarial purposes by the Mosetene. The following extracts were moderately active: Jacaratia digitata inner bark and Momordica charantia aerial part (both traditionally used as febrifuge), Kalanchoe pinnate aerial part (used in inflammatory processes), Lunania parviflora twigs and leaves, Phyllanthus acuminatus (used as piscicide), Tynanthus schumannianus fruit (used against diarrhoea), Triumfetta semitrilobata (used as febrifuge, to alleviate kidney and gynecological pain) and finally Solanum mammosum fruit (used against scabies). We present here the results of this screening, emphazing on the in vivo antimalarial activity of the selected plants. The antimalarial in vivo activity of the selected species, in relation with their traditional Mosetene use is then discussed.

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 µg/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 µg/mL. The highest cytotoxic activities were found with the petroleum ether extracts without alkaloids and with all alkaloids isolated (IC50 < 9 µg/mL for Vero cell line). Copyright

Activité antiparasitaire d'alcaloïdes bisbenzylisoquinoleiques. I: activité in vitro sur des promastigotes de trois souches de Leishmania

Leishmaniasis caused by protozoan Leishmania ssp., is an endemic parasitic disease in Central and South America. The chemotherapeutic agents against Leishmania ssp. (pentavalent antimony compounds, pentamidine and amphothericine B) are toxic and expensive products. Basing on the Bolivian folk medicine, we tried to find new active principles. Fourteen isoquinoline alkaloids, especially bisbenzylisoquinoline alkaloids extracted from Annonaceae, Berberidaceae, Hernandiaceae and Menispermaceae, demonstrate highly effective activity against this protozoan. Among them gyrocarpine, daphnandrine and obaberine seem to be of particular interest. The therapeutic effect was studied by biological assays on culture forms in vitro three strains of Leishmania, L. donovani, L. braziliensis (cutaneous and mucocutaneous leishmaniasis), L. mexicana amazonensis (cutaneous) and L. donovani (visceral leishmaniasis).

Variation of leishmanicidal activity in four populations of Urechites andrieuxii

Urechites andrieuxii Muell.-Arg. (Apocynaceae) is widely used in the Yucatan Peninsula for the treatment of cutaneous leishmaniasis. The influence of the environment in the variability of the leishmanicidal activity of the plant was evaluated using crude methanol extracts of roots from individuals belonging to four natural populations growing in the Yucatan Peninsula. The results of the growth inhibition test using three Leishmania spp. promastigotes showed a stronger leishmanicidal activity in populations of U. andrieuxii growing in more humid environments. Further evaluation against four human cancer cell lines and in the brine shrimp bioassay of both extracts from various parts of the plant and from the most active methanol root extracts, suggested that while the leaf extract appears to have selective toxicity against Leishmania parasites, the strong leishmanicidal activity detected in the root extracts of the plant might be due to its cytotoxicity.

Leishmanicidal activity of some stilbenoids and related heterocyclic compounds.

We have evaluated the leishmanicidal activity of some natural and semisynthetic dihydrostilbenoids and several compounds of other series of dihydrostilbamides, isoindoles, phthalazinones, imidazoisoindoles and pyrimidoisoindoles. The evaluation was performed in vitro, on cultures of cutaneous, mucocutaneous and visceral strains of Leishmania spp. The most potent and selective compounds of these series were the dihydrostilbene piperidides.

Antimalarial Activity of Alkaloids from Pogonopus tubulosus

The antimalarial activity of the Bolivian medicinal plant Pogonopus tubulosus (D.C.) Schumann was evaluated by in vitro testing on trophozoite stages of resistant and sensitive strains of Plasmodium falciparum and by in vivo tests on P. berghei and P. vinckei petteri in mice. The bark of this medicinal plant yielded three alkaloids: tubulosine, psychotrine, cephaeline. Tubulosine showed an interesting activity in vitro with an IC50 of 0.006 μg/mL against the sensitive strain of P. falciparum and an IC50 of 0.011 μg/mL against the resistant strain of P. falciparum. This compound had good in vivo antimalarial activity with an ED50 of 0.05 mg/kg/day on P. vinckei petteri strain and an ED50 of 0.45 mg/kg/day on P. berghei.