No / Cassia siamea L. (Fabaceae) was identified from the southwest Nigerian ethnobotany as a remedy for febrile illness. This led to the bioassay-guided fractionation of stem bark of the plant extract, using the parasite lactate dehydrogenase assay and multi-resistant strain of Plasmodium falciparum (K1) for assessing the in vitro antimalarial activity. Emodin and lupeol were isolated from the ethyl acetate fraction by a combination of chromatographic techniques. The structures of the compounds were determined by spectroscopy, co-spotting with authentic samples and comparison with literature data. Both compounds were found to be the active principles responsible for the antiplasmodial property with IC50 values of 5 µg/mL, respectively.

No / The aim of this chapter is to illustrate some current developments in natural product-derived antimalarial drugs. Traditional medicines have provided two of our most important antimalarial drugs (quinine and artemisinin) and have the potential to provide many novel antimalarial lead compounds of which several examples will be discussed. In addition, well- known natural antimalarials such as artemisinin continue to be an important focus of research and there is also increasing interest in investigating natural product sources that have not been traditionally used as antimalarials such as marine species of plants and animals. Assays based on specific malaria parasite targets such as thioredoxin reductase and heat shock protein have been employed to screen extracts and/or compounds and these have resulted in the identification of a number of potentially interesting antiplasmodial agents. However, since many victims of malaria are unable to afford antimalarial drugs, another approach adopted by some charities/NGO’s is to encourage people to grow their own medicinal plants such as Artemisia annua; some recent studies on this theme will be discussed.

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No. of bitstreams: 1 Tese - Diego de Moura Rabelo.pdf: 4209565 bytes, checksum: c31aba4b7094e32cdf712295f847ad9b (MD5) Previous issue date: 2014-02-28 / FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas / The rapid growth of resistance of bacteria and malaria parasites against currently available drugs creates an urgent need for new therapeutic approaches. The Annonaceae family, because its history in ethnomedicine and chemical and pharmacological potential, evidenced in the literature, represents a promising natural source of biological active molecules to combat these diseases. In the present study we evaluated, preliminarily, antiplasmodial activities of hydroalcoholic extracts of the leaves of Unonopis guatterioides, Anaxagorea brevipes, Duguetia riparia, Tetrameranthus duckei, Annona exsucca, Xylopia benthamii and Guatteria citriodora species. Among the evaluated species, only Guatteria citriodora showed potential antiplasmodial activity with IC50 equal to 1.0685 and p-value of 0.540. The evaluation of antiplasmodial activity of hexane fractions (FHF and FHG), alkaloidic (FAF and FAG) and neutral (FNF and FNG) derived from the partitioning of the crude hydroalcoholic extracts of leaves (EHBF) and branches (EHBG) of this species, directed the phytochemical studies for promising fractions, so the alkaloid fractions were selected. In addition, the antibacterial activities of EHBF and EHBG, FHF and FHG, FAF and FAG, FNF and FNF and essential oils of the leaves were also evaluated. The evaluation of antiplasmodial activity were performed against Plasmodium falciparum by flow cytometry, and for the antimicrobial activity the technique of agar disk diffusion were used against several gram positive and gram negative pathogenic bacteria. The fractions FHG, FAF and FAG proved to be the most active for antiplasmodial activity with IC50 of 1.035 μg.mL-1 (p-value 0.57), 1.0685 μg.mL-1 (p-value 0.54) e 0.332 μg.mL-1 (p-value 0.26), respectively. Bacillus subtilis proved to be very sensitive front FAF and FAG showing zone of inhibition of 22 mm and 21mm respectively, both fractions with minimum inhibitory concentration (MIC) equal to 62.5 μg.mL-1. Enterococcus faecalis showed moderately sensitive to FAF with xix inhibition zone of 17 mm and MIC equal to 125 μg.mL-1. A significant antibacterial activity was observed for the essential oils from the leaves, against Gram-negative bacteria Escherichia coli and Salmonella typhimurium EPEC which proved moderately sensitive to essential oils since they showed inhibition halos between the average of 11 and 13 mm, respectively, both with CIM equal to 125 μg.mL-1. The alkaloid fractions of leaves and twigs of Guatteria citriodora species selected by phytochemical study were analyzed by ESI-IT-MS and their chromatographic profile revealed the presence of several ion pair mass, which were consistent with the presence of protonated ions of aporphine alkaloids. From the chromatographic fractionation of these fractions seven alkaloids were isoleted, and they were identified by nuclear magnetic resonance of 1H and 13C (1D and 2D), such as the alkaloids: liriodenine, lyisicamine, O-methylmoschatoline and 3-methoxyoxoputerine (oxoaporphine), 3-methoxyguadiscidine (aporphine), palmatine (protoberberine) and guattescidine (7-hydroxy-7-methylaporphine). With the exception of liriodenine and O-methylmoschatoline, isolated from the bark of G. citriodora by Rabelo (2008), other structures are reported for the first time in the species. The antiplasmodial activities in vitro of FAF and FAG fractions are promising and may be associated with their alkaloidal constituents, which encourages deeper studies including in vivo investigations to establish its true efficacy and toxicity, providing data to obtaining new antimalarial drugs from vegetable source. / O rápido crescimento da resistência de bactérias e parasitas da malária contra as drogas atualmente disponíveis gera uma necessidade urgente de novas abordagens terapêuticas. A família Annonaceae, pela sua história na etnomedicina e potencial químico e farmacológico, evidenciado na literatura, representa uma fonte natural promissora de moléculas biologicamente ativas para combate a estes patôgenos. No presente trabalho, foram avaliadas, preliminarmente, as atividades antiplasmódicas dos extratos hidroalcoólicos das folhas das espécies Unonopis guatterioides, Anaxagorea brevipes, Duguetia riparia, Tetrameranthus duckei, Annona exsucca, Xylopia benthamii e Guatteria citriodora. Das espécies avaliadas somente a Guatteria citriodora evidenciou potencial atividade antiplasmódica com CI50 igual a 1,0685 e p-valor de 0,540. A avaliação de atividade antiplasmódica das frações hexânicas (FHF e FHG), alcaloídicas (FAF e FAG) e neutras (FNF e FNG), oriundas do particionamento dos extratos hidroalcoólicos brutos das folhas (EHBF) e galhos (EHBG) desta espécie, direcionou o estudo fitoquímico para as frações mais promissoras, sendo selecionadas as frações alcaloídicas. Adicionalmente, foram avaliadas as atividades antibacterianas de EHBF e EHBG, FHF e FHG, FAF e FAG, FNF e FNG e dos óleos essenciais de suas folhas. A avaliação da atividade antiplasmódica foram realizadas frente ao Plasmodium falciparum por citometria de fluxo, e para avaliação da atividade antimicrobiana utilizou-se a técnica de difusão em ágar contra diversas bactérias Gram positivas e Gram negativas. As frações FHG, FAF e FAG mostraram-se as mais ativas para atividade antiplasmódica com CI50 de 1,035 μg.mL-1 (p-valor 0,57), 1,0685 μg.mL-1 (p-valor 0,54) e 0,332 μg.mL-1 (p-valor 0,26), respectivamente. Na avaliação antibacteria Bacillus subtilis apresentou-se muito sensível frente a FAF e FAG com halos de inibição de 22 mm e 21 mm, respectivamente, sendo ambos com concentração inibitória mínima (CIM) igual a xxi 62,5 μg.mL-1. Enterococcus faecalis mostrou-se moderadamente sensível a FAF com halo de inibição de 17 mm e CIM igual a 125 μg.mL-1. Foi observada atividade antibacteriana ainda para os óleos essenciais das folhas, com CIM igual a 125 μg.mL-1, contra as bactérias Gram negativas Escherichia coli EPEC e Salmonella typhimurium que se apresentaram moderadamente sensíveis por evidenciarem halos de inibição em média de 11 e 13 mm, respectivamente. As frações alcaloídicas das folhas e galhos finos da espécie Guatteria citriodora, selecionadas para estudo fitoquímico, foram analisadas por ESI-IT-MS e o seu perfil cromatográfico evidenciou a presença de vários íons de massa par, compatíveis com a presença de íons protonados dos alcaloides aporfínicos. O fracionamento cromatográfico destas frações levou ao isolamento de 7 alcaloides, identificados por RMN de 1H e 13C (1D e 2D), como os alcaloides, liriodenina, lisicamina, O-metilmoschatolina e 3-metoxioxoputerina (oxoaporfínicos), 3-metoxiguadiscidina (aporfínico), palmatina (protoberberinico) e guattescidina (7-hidroxi-7-metilaporfíninicos). Com exceção da liriodenina, lisicamina e O-metilmoschatolina, isoladas anteriormente da casca do caule de G. citriodora por Rabelo (2008), as demais estruturas são relatadas pela primeira vez para esta espécie. As atividades antiplasmódicas das frações FAF e FAG in vitro são promissoras e podem ser associadas aos seus constituintes alcaloídicos encorajando o aprofundamento dos estudos com investigações in vivo, para estabelecer sua verdadeira eficácia e toxicidade, visando fornecer ubsídios para a obtenção de novos fármacos antimaláricos de origem vegetal.

Malaria affects hundreds of millions of people worldwide and equally claims hundreds of thousands of lives each year. With the current spread of drug resistance to standard antimalarial drugs like chloroquine and the emergence of artemisinin-resistant parasites, new antimalarial drugs and formulations are urgently needed. An ethnobotanical survey was carried out in this study in search of novel compounds with promising antiplasmodial activity. Using the ethnobotanical approach, a total of 61 plant species from 59 genera distributed in 34 plant families were found to be used traditionally for the treatment of malaria in Nigeria. Biological evaluation of the plant¿s methanolic extracts was assessed using the parasite lactate dehydrogenase (pLDH) assay against the chloroquine-sensitive (3D7) and chloroquine-resistant (K1) strains of Plasmodium falciparum. A total of five (5) plant species showed more potent antiplasmodial activities against the malaria parasites. These are Acanthospermum hispidum, Cassia occidentalis, Kaempferia aethiopica Prosopis africana and Physalis angulata with MIC values ranging between 7.815µg/ml to 31.25µg/ml (3D7 strain) and 15.63µg/ml to 62.50µg/ml (K1 strain) against the malaria parasites, respectively. Two plants, Prosopis africana (Leguminosae-mimosoideae) and Physalis angulata (Solanaceae) were selected for further study. The phytochemical investigation of the active chloroform extracts of P. africana and P. angulata yielded several compounds with three known alkaloids, namely, prosopinine (I), prosopine (II) and acetamide (III). Their structures were confirmed by MS, 1D and 2D NMR spectroscopy. Compounds I, II and III have moderate in vitro antiplasmodial activity against the malaria parasites. Both chloroquine and artemether were used as standard control. / Association of Commonwealth Universities and the Commonwealth Scholarship Commission in the UK (Commonwealth Scholarship Reference Number: NGCS-2005-259).

As a part of the continuing search for bioactive compounds with the Madagascar International Cooperative Biodiversity Group (ICBG), and in collaboration with the Natural Products Discovery Institute of the Institute for Hepatitis and Virus Research (IHVR), thirteen plant extracts were investigated for antiplasmodial activity, thirteen plant extracts were investigated for antiproliferative activity, and one extract was investigated for inhibitors of the shikimate pathway in Plasmodium falciparum. Bioassay-guided fractionation of the extracts led to the identification of nineteen compounds with both antiplasmodial and antiproliferative activity, and thirteen compounds with only antiproliferative activity. Thirteen of these compounds (2.1 – 2.9, 3.3, 3.4, 4.5, and 5.1) were previously unknown. In addition total synthesis was used to confirm the structure of one new compound (4.5) and two other new natural-product like compounds (4.6 and 4.7) were also synthesized and investigated for antiplasmodial activity. / Ph. D.

No / A series of analogues of cryptolepine (1) have been synthesized and evaluated for their in vitro antiplasmodial and cytotoxic properties. The IC50 values of several compounds (11a, 11k¿m, 11o, 13) against Plasmodium falciparum (strain K1) were <0.1 ¿M, 5¿10-fold lower than that of 1 but their cytotoxicities were only 2¿4 times greater than that of 1. Compounds with a halogen in the quinoline ring and a halogen or a nitro group in the indole ring have enhanced antiplasmodial activity. In mice infected with P. berghei, the 7-bromo-2-chloro (11k) and 2-bromo-7-nitro (13) derivatives of 1 suppressed parasitemia by >90% at doses of 25 mg kg-1 day-1 with no apparent toxicity to the mice. 2,7-Dibromocryptolepine (15) was evaluated at several dose levels, and a dose-dependent suppression of parasitemia was seen (ED90 = 21.6 mg kg-1 day-1). The antimalarial mode of action of 1 appears to be similar to that of chloroquine and involves the inhibition of hemozoin formation. A number of analogues were assessed for their effects on the inhibition of ß-hematin (hemozoin) formation, and the results were compared with their antiplasmodial activities having taken account of their predicted accumulation into the acidic parasite food vacuole. No correlation was seen (r2 = 0.0781) suggesting that the potent antimalarial activity of compounds such as 15 involves other mechanisms in addition to the inhibition of hemozoin formation.

No / Medicinal plants used to treat infectious diseases in Bunda district, Tanzania, were screened for activity against Plasmodium falciparum and human Immunodeficiency Virus Type 1 (HIV-1, IIIB strain) and Type 2 (HIV-2, ROD strain). Antiplasmodial activity was observed for the 80% MeOH extract of Ormocarpum kirkii (root; MIC = =31.25 ¿g/mL). Combretum adenogonium (leaves), Euphorbia tirucalli (root), Harrisonia abyssinica (root), Rhyncosia sublobata (root), Sesbania sesban (root), Tithonia diversifolia (leaves), and Vernonia cinerascens (leaves; MIC value of 62.5 ¿g/mL). With regard to HIV, 80% MeOH extracts of Barleria eranthemooides (root), Cambretum adenogonium (leaves and stem bark), Elaeodedron schlechteranum (stem bark and root bark), Lannea schweinfurthii (stem bark), Terminalia mollis (stem bark and root bark), Acacia tortilis (stem bark), Ficus cycamorus (stem bark) and Indigofera colutea (shoot), as well as H2O extracts from Barleria eranthemoides (root), Combretum adenogonium (leaves and stem bark)and Terminalia mollis (stem bark and root bark) exhibited IC50 values below 10 ¿g/mL against HIV-1 (IIIB strain). The highest anti-HIV-1 activity value was obtained for the B. eranthemoides 80% MeOH root extract (IC50 value 2.1 ¿g/mL). Only a few extracts were active against HIV-2, such as the 80% MeOH extract from Lannea schweinfurthii (stem bark) and Elaeodedron schlechteranum (root bark), showing IC50 values < 10 ¿g/mL.

No / Background In traditional medicine whole plants or mixtures of plants are used rather than isolated compounds. There is evidence that crude plant extracts often have greater in vitro or/and in vivo antiplasmodial activity than isolated constituents at an equivalent dose. The aim of this paper is to review positive interactions between components of whole plant extracts, which may explain this. Methods Narrative review. Results There is evidence for several different types of positive interactions between different components of medicinal plants used in the treatment of malaria. Pharmacodynamic synergy has been demonstrated between the Cinchona alkaloids and between various plant extracts traditionally combined. Pharmacokinetic interactions occur, for example between constituents of Artemisia annua tea so that its artemisinin is more rapidly absorbed than the pure drug. Some plant extracts may have an immunomodulatory effect as well as a direct antiplasmodial effect. Several extracts contain multidrug resistance inhibitors, although none of these has been tested clinically in malaria. Some plant constituents are added mainly to attenuate the side-effects of others, for example ginger to prevent nausea. Conclusions More clinical research is needed on all types of interaction between plant constituents. This could include clinical trials of combinations of pure compounds (such as artemisinin + curcumin + piperine) and of combinations of herbal remedies (such as Artemisia annua leaves + Curcuma longa root + Piper nigum seeds). The former may enhance the activity of existing pharmaceutical preparations, and the latter may improve the effectiveness of existing herbal remedies for use in remote areas where modern drugs are unavailable.

No / In the search for biologically active plant species, many studies have shown that an ethnopharmacological approach is more effective than a random collection. In order to determine whether this is true in the case of plant species used for the treatment of malaria in Orissa, India, the antiplasmodial activities of extracts prepared from 25 traditionally used species were compared with those of 25 species collected randomly. As expected, plant species used traditionally for the treatment of malaria were more likely to exhibit antiplasmodial activity (21 species (84%) active against Plasmodium falciparum strain 3D7) than plant species collected randomly (9 species (32%)). However, of the nine active randomly collected species, eight had not previously been reported to possess antiplasmodial activity while one inactive species had been reported to be active in another study. Of the 21 active species of traditional antimalarial treatments, only six had been reported previously. This study suggests that while the selection of traditional medicinal plants is more predictive of antiplasmodial study, random collections may still be of value for the identification of new antiplasmodial species.

MSc (Chemistry) / Department of Chemistry / Rauvolfia caffra Sond, a species of evergreen trees and shrubs in the dogbane family, (Apocynaceae), is used as a medicinal plant among traditional communities in many countries for the treatment of malaria, diabetes, coughs, gastrointestinal disturbances, skin infections, impotence, insomnia, diarrhoea, dysentery, scabies, worm infections, and both parasitic and microbial infections. Phytochemical studies have revealed that indole alkaloids are the major constituents of the stem bark. However, there are limited studies linking the compounds with the ethnomedicinal uses. The aim of this study is to isolate and characterize bioactive compounds from Rauvolfia caffra Sond. The highest phenolic content found in a fraction was 16.06±0.125 mg GAE/g, while the highest flavonoid content measured was 9.453±0.081 mg QE/g. In the DPPH free radical scavenging activity and reducing power tests, a lowest IC50 value of 0.022±0.003 μg/mL and IC0.5 value 0.518±0.044 μg/mL, respectively, was found. Six compounds were isolated from the stem bark, including lupeol, a pentacyclic tri-terpenoid isolated for the first time from the genus Rauvolfia; raucaffricine, a rare glycoalkaloid of the monoterpenoid indole class; N-methylsarpagine, an indole alkaloid isolated for the time from R. caffra and spegatrine, an indole alkaloid isolated for the first time from R. caffra, respectively. Concerning antimicrobial activity, the highest activity of a fraction was against B. cereus with MIC values as low as 12.5 mg/mL. One fraction at the tested concentration (250 μg/mL) decreased the viability of Plasmodium falciparum (4.149±6.979 %) with an IC50 value of 6.533 μg/mL. The crude extract and some fractions affected the viability of the Trypanosomes at the tested concentration (250 μg/mL), giving -0.133 ± 0.206 %, 11.334 ± 2.692 %, 1.026 ± 0.143 % and 20.769 ± 9.054 % with IC50 values of 18.50 μg/mL, 14.15 μg/mL, 15.58 μg/mL and 34.71 μg/mL, respectively. Furthermore, the fractions did not show significant cytotoxic effects at a concentration of 50 μg/mL. / NRF