Quantitative standardization of pharmacologically active components from antiplasmodial plant Solanum nudum Dunal (wild and in vitro) / Estandarización cuantitativa de componentes farmacológicamente activos de la planta antiplasmodial Solanum nudum Dunal (silvestre e in vitro)

Solanum nudum Dunal (Solanaceae) is most commonly known andused by the population of the colombian Pacific coast as an antimalarial treatment. This article study into optimization and quantitative analysis of compounds steroidal over time of development of this species when grown in vitro and wild. A new steroidal compound named SN6 was elucidated by NMR and a new method of quantification of seven steroidal compounds (Diosgenone DONA and six steroids SNs) using HPLC-DAD-MS in extracts of cultures in vitroand wild was investigated. Biology activity of extracts was found to a range of antiplasmodial activity in FCB2 and NF-54 with inhibitory concentration (IC50) between (17.04 -100µg/mL) and cytotoxicity in U-937 of CC50 (7.18 -104.7µg/mL). This method creates the basis for the detection of seven sterols antiplasmodial present in extracts from S. nudum plant as a quality parameter in the control and expression of phytochemicals.

Solanum nudum Dunal (Solanaceae) es el más conocido y utilizado por la población de la costa del Pacífico colombiano como tratamiento antipalúdico. Este artículo estudia la optimización y el análisis cuantitativo de compuestos esteroides a lo largo del tiempo de desarrollo de esta especie cuando se cultiva in vitro y en forma silvestre. Un nuevo compuesto esteroideo llamado SN6 fue dilucidado por RMN y se investigó un nuevo método de cuantificación de siete compuestos esteroides (Diosgenone DONA y seis esteroides SN) usando HPLC-DAD-MS en extractos de cultivos in vitro y silvestres. La actividad biológica de los extractos se encontró en un rango de actividad antiplasmodial en FCB2 y NF-54 con concentración inhibitoria (IC50) entre (17.04 -100 µg/mL) y citotoxicidad en U-937 de CC50 (7.18 -104.7 µg/mL). Este método crea la base para la detección de siete esteroles antiplasmodiales presentes en extractos de planta de S. nudum como parámetro de calidad en el control y expresión de fitoquímicos.

Insights into cytochrome bc1 complex binding mode of antimalarial 2-hydroxy-1, 4-naphthoquinones through molecular modelling

BACKGROUND Malaria persists as a major public health problem. Atovaquone is a drug that inhibits the respiratory chain of Plasmodium falciparum, but with serious limitations like known resistance, low bioavailability and high plasma protein binding. OBJECTIVES The aim of this work was to perform molecular modelling studies of 2-hydroxy-1,4-naphthoquinones analogues of atovaquone on the Qo site of P. falciparum cytochrome bc1 complex (Pfbc1) to suggest structural modifications that could improve their antimalarial activity. METHODS We have built the homology model of the cytochrome b (CYB) and Rieske iron-sulfur protein (ISP) subunits from Pfbc1 and performed the molecular docking of 41 2-hydroxy-1,4-naphthoquinones with known in vitro antimalarial activity and predicted to act on this target. FINDINGS Results suggest that large hydrophobic R2 substituents may be important for filling the deep hydrophobic Qo site pocket. Moreover, our analysis indicates that the H-donor 2-hydroxyl group may not be crucial for efficient binding and inhibition of Pfbc1 by these atovaquone analogues. The C1 carbonyl group (H-acceptor) is more frequently involved in the important hydrogen bonding interaction with His152 of the Rieske ISP subunit. MAIN CONCLUSIONS Additional interactions involving residues such as Ile258 and residues required for efficient catalysis (e.g., Glu261) could be explored in drug design to avoid development of drug resistance by the parasite.

Successful application of virtual screening and molecular dynamics simulations against antimalarial molecular targets

The main challenge in the control of malaria has been the emergence of drug-resistant parasites. The presence of drug-resistant Plasmodium sp. has raised the need for new antimalarial drugs. Molecular modelling techniques have been used as tools to develop new drugs. In this study, we employed virtual screening of a pyrazol derivative (Tx001) against four malaria targets: plasmepsin-IV, plasmepsin-II, falcipain-II, and PfATP6. The receiver operating characteristic curves and area under the curve (AUC) were established for each molecular target. The AUC values obtained for plasmepsin-IV, plasmepsin-II, and falcipain-II were 0.64, 0.92, and 0.94, respectively. All docking simulations were carried out using AutoDock Vina software. The ligand Tx001 exhibited a better interaction with PfATP6 than with the reference compound (-12.2 versus -6.8 Kcal/mol). The Tx001-PfATP6 complex was submitted to molecular dynamics simulations in vacuum implemented on an NAMD program. The ligand Tx001 docked at the same binding site as thapsigargin, which is a natural inhibitor of PfATP6. Compound TX001 was evaluated in vitro with a P. falciparum strain (W2) and a human cell line (WI-26VA4). Tx001 was discovered to be active against P. falciparum (IC50 = 8.2 µM) and inactive against WI-26VA4 (IC50 > 200 µM). Further ligand optimisation cycles generated new prospects for docking and biological assays.

Blood shizonticidal activities of phenazines and naphthoquinoidal compounds against Plasmodium falciparum in vitro and in mice malaria studies

Due to the recent advances of atovaquone, a naphthoquinone, through clinical trials as treatment for malarial infection, 19 quinone derivatives with previously reported structures were also evaluated for blood schizonticide activity against the malaria parasite Plasmodium falciparum. These compounds include 2-hydroxy-3-methylamino naphthoquinones (2-9), lapachol (10), nor-lapachol (11), iso-lapachol (12), phthiocol (13) and phenazines (12-20). Their cytotoxicities were also evaluated against human hepatoma and normal monkey kidney cell lines. Compounds 2 and 5 showed the highest activity against P. falciparum chloroquine-resistant blood-stage parasites (clone W2), indicated by their low inhibitory concentration for 50% (IC50) of parasite growth. The therapeutic potential of the active compounds was evaluated according to the selectivity index, which is a ratio of the cytotoxicity minimum lethal dose which eliminates 50% of cells and the in vitro IC50. Naphthoquinones 2 and 5, with activities similar to the reference antimalarial chloroquine, were also active against malaria in mice and suppressed parasitaemia by more than 60% in contrast to compound 11 which was inactive. Based on their in vitro and in vivo activities, compounds 2 and 5 are considered promising molecules for antimalarial treatment and warrant further study.

Cuantificación de quinina en extractos de Cinchona pubescens y evaluación de la actividad antiplasmodial y citotóxica / Quantification of quinine in extracts from stems Cinchona pubescens and evaluation of antiplasmodial and cytotoxic activity

Plants belonging to the genus Cinchona L. (Rubiaceae), whose active ingredient is quinine, was used for centuries to treat malaria. Plants of this genus are a potential source of new structural templates in the search for new antimalarial candidates. This study aimed to the identification, quantification of quinine and other metabolites present in extracts of different polarity of the stems of Cinchona pubescens Vahl. , oxoquinovic acid isolation, antiplasmodial activity, and measuring its cytotoxic effect. The results show a high activity to antiplasmodial alkaloids extract (IC50 = 2.20 +/- 0.0325 ug/mL), cytotoxicity (CC50 = 80.2 +/- 12.2 ug/mL), and a quinine content of 21.3+/-0.0247 ppm. The compound known as acid antiplasmodial activity oxoquinovic presented in IC50 = 11.3 +/- 0.741 ug/mL, and cytotoxicity CC50 = 72.4 +/- 3.85 ug/mL. These results motivate phytochemical studies in the search for active structural analogues quinine and quinolinic core as a source of new antimalarial agents.

Las plantas pertenecientes al género Cinchona L. (familia Rubiaceae), cuyo principio activo es la quinina, fueron utilizadas durante siglos para tratar la malaria. Este género es una fuente potencial de nuevas plantillas estructurales en la búsqueda de nuevos candidatos antimaláricos. El presente trabajo tuvo como objetivo la identificación y, cuantificación de la quinina y de otros metabolitos presentes en los extractos de diferente polaridad, de los tallos de Cinchona pubescens Vahl. , el aislamiento del ácido oxoquinóvico, la actividad antiplasmodial y, además, la medición de su efecto citotóxico. Los resultados muestran una alta actividad antiplasmodial para el extracto de los alcaloides (IC50 = 2,20 +/- 0,0325 ug/mL), una baja citotoxicidad (CC50 = 80,2 +/- 12,2 ug/mL), y un alto contenido de quinina el cual fue 21,3+/-0,0247 ppm. El compuesto ácido oxoquinóvico presentó una actividad antiplasmodial de IC50 = 11,3 +/- 0.741 ug/mL, y una citotoxicidad de CC50 = 72,4 +/- 3,85 ug/mL. Estos resultados motivan los estudios fitoquímicos en la búsqueda de principios activos y análogos estructurales en diferentes especies de Cinchonas como una fuente de nuevos agentes antimaláricos.

In vivo Study of Antiplasmodial Activity of Terminalia avicennioides and Its Effect on Lipid Profile and Oxidative Stress in Mice Infected with Plasmodium berghei.

Aims: To determine the antiplasmodial activity of methanolic extract of T. avicennioides and its effect on oxidative stress and the lipid profiles in mice infected with Plasmodium berghei. Study Design: Mice used for this study were grouped into five. The first group was not infected with malaria parasite (normal control), the second group was infected with the parasite but not treated with antimalarial drugs (negative control), the third group was infected with the parasite and treated with 5mg/kg body weight of artesunat (positive control), while the fourth and fifth groups were infected with malaria parasite and treated with 100 and 200mg/kg of T. avicennioides respectively. Methodology: The parasitaemia was monitored for five days. The animals were sacrificed on the fifth day and the blood was collected. The serum was used to assess the biochemical parameters using randox kits. Results: While parasite density increases in the negative control per day, there was reduction in parasite density in treated groups. The parasite clearance was significantly higher (P = .05) in those treated with 200mg/kg of T. avicennioides than those treated with 100mg/kg of T. avicennioides and 5mg/kg of artesunat. The malondialdehyde level was significantly higher in the negative control, while superoxide dismutase and catalase levels were significantly reduced when compared with group treated with 200mg/kgbdwt of T. avicennioides. HDL level was significantly higher (P = .05) in those treated with 200mg/kg than in the normal, negative and positive control. The triglycerides level was significantly higher in the negative control when compared with the group treated with the extract of T. avicennioides. Conclusion: This study showed that the methanolic extract of T. avicennioides display dose-related in vivo antiplasmodial and antioxidant activities as well as reduced the serum and liver lipoprotein cholesterol in mice infected with P. berghei.

Síntesis y evaluación preliminar de la posible actividad antimalárica y antineoplásica de derivados 7-cloroquinolina-4-sustituidos / Synthesis and preliminary evaluation of antimalarial and antineoplastic possible activity of 7-chloroquinoline-4-substituted derivatives

En el presente trabajo se describe la síntesis y la evaluación de la posible actividad Antimalárica y Antineoplásica de una serie de derivados 7-cloroquinolina-4-sustituidos. La estrategia empleada para la síntesis comienza con las obtención de los intermediarios clave 1-(3 ó 4-(7-cloroquinolin-4-ilamino)fenil)etanona (2 y 3) mediante una sustitución nucleofílica aromática entre la 4,7-dicloroquinolina y la 3 y/o 4-amino acetofenona. Los derivados (E)-1-(3 ó 4-(7-cloroquinolin-4-ilamino)fenil)-3-(fenilsustituido)prop-2-eno-1-ona (4 y 5), se sintetizaron a través de una condensación aldólica de Claisen-Schmidt entre los intermediarios clave y diferentes benzaldehídos sustituidos. Los derivados 7-cloro-N-(3 ó 4-(4,5-dihidro-5-(fenilsustituido)-1H-pirazol-3-il)fenil)quinolin-4-amina (6 y 7) y los 1-(3 ó 4-(7-cloroquinolin-4-ilamino)fenil)-3-(fenilsustituido)propano-1-ona (8 y 9) se diseñaron por modificación molecular de la cetona a,b-insaturada de los compuestos finales 4 y 5, (metodología clásica de la Química Medicinal) para obtener dichos derivados rígidos 6 y 7, mediante la formación de un anillo D2-pirazolina y flexibles 8 y 9, a través de su reducción. La síntesis de los derivados 6 y 7 se realizó mediante una reacción de ciclo-condensación con hidrazina monohidratada y los derivados 8 y 9, se obtuvieron a través de una hidrogenación catalítica. En la evaluación de la actividad Antimalárica in vitro se evidenció que los derivados 4, 5, 6 y 7, mostraron actividades inhibitorias la formación de la b hematina importantes (superior al 70 %), siendo los más activos: 4l, 5g, 5c, 5g y 6e, 6f con valores comparable al de la CQ. En la evaluación Antimalárica in vivo se encontró que el derivado 4e fue el más activo con 26,4 días de sobrevivencia post-infección (230 % de incremento) y una parasitemia de 2,4 % (96 % de reducción). Con respecto a los resultados obtenidos en el efecto de estos derivados sobre la viabilidad y proliferación de las líneas celulares neoplásicas Jurkat E6.1, HL60, MCF-7 y A549, los compuestos 4a, 4g, 4l, 4m y 6e mostraron la mayor actividad inhibitoria del crecimiento de las células leucémicas HL60 después de 24h de tratamiento con valores de CI50 de 1,19 µM, 1,08 µM, 0,59 µM, 0,43 µM y 0,94 µM (hasta 3 y 100 veces más activos que la doxorubicina y que la CQ, respectivamente). En lo referente a la evaluación de la actividad proapoptótica en las líneas celulares neoplásicas Jurkat E6.1, HL60, MCF-7 y A549, se evidenció que los derivados 4, 5 y 6, al igual que los controles, generaron un aumento en el porcentaje de células positivas para la Anexina V/FITC dependiente de la dosis (apoptosis temprana y tardía). Ninguno de estos derivados indujo el proceso de necrosis en estas células.

The present investigation describes the synthesis and evaluation of the Antimalarial and Antineoplastic activity possible a series of derivatives of 7-substituted-4-chloro-quinoline. The strategy employed for the synthesis begins with preparation of the key intermediate 1-(3 or 4-(7-chloroquinolin-4-ylamino) phenyl)ethanone (2and 3) by a nucleophilic aromatic substitution between 4,7-dichloroquinoline and the 3 and/or4-amino acetophenone. The derivatives (E)-1-(3 or 4-(7-chloroquinolin-4-ylamino) phenyl)-3-(substitutedphenyl)prop-2-en-1-one (4and 5), were synthesized a through aldol condensation Claisen-Schmidt among different key intermediates and substituted benzaldehydes. The resulting 7-chloro-N-(3 or 4-(4,5-dihydro-5-(substitutedphenyl)-1H-pyrazol-3-yl)phenyl)quinolin-4-amine (6 and 7) and 7-chloro-4-[(3 or 4-(substituted phenyl)ethylcarbonyl)phenyl]aminoquinoline(8 and 9) were designed for the molecular modification , -unsaturated ketone of the final compounds 4and 5 (classic methodology Medicinal Chemistry) for said rigid derivatives 6and 7, through the formation of a 2-pyrazoline ring flexible and 8and 9, through its reduction. The synthesis of derivatives 6and 7were performed using a cycle-condensation reaction with hydrazine monohydrate and 8and 9derivatives were obtained via a catalytic hydrogenation. In the assessment of antimalarial activity in vitro was demonstrated that derivatives 4, 5, 6and 7showed inhibitory activities forming the major hematin (above 70%), being more active: 4l, 5g, 5c, 5g, 6eand 6f,with values comparable to that of CQ. In vivoantimalarial evaluation found that the derivative 4ewas most active with survival 26.4 dayspost-infection (230% increase) and a parasitemia of 2.4% (96% reduction). With regard to the results on the effect of these derivatives on the viability and proliferation of neoplastic cell lines Jurkat E6.1, HL60, MCF-7 and A549, compounds 4a, 4g, 4l,4mand 6eshow greater activity growth inhibitory HL60 leukemia cells after 24 h of treatment with IC50values of 1.19µM, 1.08µM, 0.59µM, 0.43µMand 0.94 M (to 3 and 100 times more active than doxorubicin and the CQ, respectively). Regarding the evaluation of pro-apoptotic activity on neoplastic cell lines Jurkat E6.1, HL60, MCF-7 and A549, was demonstrated that derivatives 4, 5and 6, like the controls, an increase in generated percentage of cells positive for Annexin V/FITC dose dependent (early andlate apoptosis). None of these derivatives induced necrosis process in these cells.

Evaluation of the physicochemical equivalence of three brands of commercially available quinine sulphate tablets from South Western part of Nigeria

BACKGROUND:The relatively little resistance to quinine globally has led to an increase in its use in P. falciparum malaria especially in multi-drug resistant strains.OBJECTIVE:To evaluate the physicochemical and equivalency of three brands of quinine sulphate tablets available in South Western region of Nigeria.METHODS:The pharmaceutical and chemical equivalence of three brands of quinine sulphate tablets were assessed through the evaluation of some biopharmaceutical parameters and active drug content. RESULTS:All the brands complied with the official specification for uniformity of weight. Two of the brands (A & B) gave similar crushing strengths while the third brand (C) gave a much lower value. Similarly all the brands complied with the official specification of disintegration test but the obtained values were statistically different (p<0.05). The T(70) obtained from the dissolution rate profile was less than 45 minutes for the three brands, although A and B were not statistically different but C was statistically from A and B. The quinine content of brands B and C are within the official specification however brand A with percentage content of 110±1.3%w/w, is above the specification while it is statistically different from the other brands. CONCLUSION:Brands B and C could be regarded as chemical equivalent, but they are not biopharmaceutical equivalents, on the other hand, brands A and B may be regarded as biopharmaceutical equivalents but not chemical equivalent

Quantitation of artemether in pharmaceutical raw material and injections by high performance liquid chromatography / Quantificação de artemether a matéria-prima farmacêutica e injeções por cromatografia líquida de alto desempenho

The quantitation of artemether in both pharmaceutical raw material and injections was carried out by high performance liquid chromatography (HPLC) with ultraviolet detection. A Zorbax C18 column (150 x 4.6 mm; 5 μm), at 30 ºC, and a mobile phase composed of acetonitrile and water (70:30), at a flow rate of 1ml/min, were used. The detection wavelength was 216 nm and the injection volume was 20 μL. The method proved to be linear (r²=0.9999), precise (RSD < 20 percent for intra-day and inter-day precision), accurate and selective regarding possible impurities and excipients of the samples. The detection and quantitation limits were 8 μg/mL and 25 μg/mL, respectively. The artemether content obtained in the raw material analysis was 99.26 percent and in the injections, 102.08 percent. The optimized and validated method may be successfully employed to perform routine quality control analyses.

A quantificação de artemeter em matéria-prima farmacêutica e solução injetável foi realizada por cromatografia líquida de alta eficiência (CLAE) com detecção na região do ultravioleta. Empregou-se coluna Zorbax C18 (150 x 4.6 mm; 5 μm), mantida a 30 ºC, e fase móvel composta por acetonitrila e água (70:30), com fluxo de 1 ml/min. A detecção foi realizada a 216 nm, e o volume de injeção foi 20 μl. O método se mostrou linear (r²=0,9999), preciso (DPR < 2,0 por cento para precisão intra-dia e inter-dias) e seletivo em relação a possíveis impurezas e excipientes das amostras. Os limites de detecção e quantificação obtidos foram 8 μg/mL e 25 μg/mL, respectivamente. O teor médio de artemeter obtido na análise da matéria-prima farmacêutica foi 99,26 por cento e na solução injetável, 102,08 por cento. O método otimizado e validado pode ser utilizado com sucesso para análises rotineiras em controle de qualidade.

Plant-derived antimalarial agents: new leads and efficient phythomedicines: part 1: Alkaloids

Malaria remains one of the most serious world health problem and the major cause of mortality and morbidity in the endemic regions. Brazil is among the 30 high-burden countries and most of the cases occur in the Legal Amazonian Region. New chemotherapeutical agents are needed for the treatment of malaria. Many plant species are used in traditional medicines of malarious countries and a relatively few number of these have been investigated for evaluation of their antimalarial effect. Still lower is the number of those that have had the active natural compounds isolated and the toxicity determined. This area is, then, of great research interest. discovery project of antimalarial natural products from plants traditionally used to treat malaria must include in vitro and in vivo assays as well as bioguided isolation of active compounds. The final products would be antimalarial chemical entities, potential new drugs or templates for new drugs development, and/or standardized antimalarial extracts which are required for pre-clinical and clinical studies when the aim is the development of effective and safe phythomedicines. This review discusses these two approaches, presents briefly the screening methodologies for evaluation of antimalarial activity and focuses the activity of alkaloids belonging to different structural classes as well as its importance as new antimalarial drugs or leads and chemical markers for phytomedicines.

A malária ainda é um dos mais sérios problemas de saúde pública e a principal causa de mortalidade e morbidade nas regiões endêmicas. O Brasil está entre os 30 países com maior incidência de malária e a maior parte dos casos ocorre na Amazônia Legal. Novos agentes terapêuticos são necessários para o tratamento da malária. Muitas espécies vegetais são utilizadas na medicina tradicional de vários países endêmicos mas é relativamente reduzido o número daquelas que já foram investigadas quanto à sua atividade antimalárica. Menor ainda é o número de espécies das quais foram isoladas substâncias ativas e tiveram sua toxidade determinada. Esta área de pesquisa é, portanto, de alta relevância. Um projeto de descoberta de produtos naturais antimaláricos a partir de plantas de uso tradicional deve incluir ensaios in vitro e in vivo bem como o isolamento biomonitorado de substâncias ativas. Os produtos finais serão substâncias naturais antimaláricas, potenciais fármacos ou protótipos para o desenvolvimento de novos fármacos, e/ou extratos padronizados, com atividade antimalárica, os quais são necessários para estudos pré-clínicos e clínicos quando o objetivo é o desenvolvimento de fitoterápicos (fitomedicamentos) eficazes e seguros. A presente revisão discute estas duas abordagens, apresenta resumidamente as metodologias de bioensaios para avaliação de atividade antimalárica e focaliza a atividade de alcalóides pertencentes a diferentes classes estruturais bem como sua importância como fármacos ou protótipos e como marcadores químicos de fitoterápicos.

In vitro bioequivalence study of nine brands of artesunate tablets marketed in Nigeria.

BACKGROUND & OBJECTIVES: The availability of numerous brands of artesunate in our drug market today places clinicians and pharmacists in a difficult situation of choice of a suitable brand or the possibility of alternative use. The aim of the present study was to predict the bioequivalence of nine brands of artesunate tablets marketed in Nigeria using in vitro tests. METHODS: The in vitro dissolution study was carried out on the nine brands of artesunate tablets using the basket method according to US Pharmacopoeia (USP) guidelines. Other general quality assessment tests like hardness and disintegration time were also determined. RESULTS: All the brands tested passed the British Pharmacopoeia (BP) standard for disintegration time. Only AT2, AT4, AT6 and AT9 passed the standard for hardness. There were significant differences in the dissolution profiles of the nine brands. All the brands except AT1, however, released >70% of artesunate within 30 min. Four of the brands AT5, AT6, AT7 and AT8 exhibited >90% dissolution in <10 min. The other brands AT1, AT2, AT3, AT4 and AT9 (innovator brand) have calculated similarity factors of 23.8, 59.8, 50, 54.8 and 100. INTERPRETATION & CONCLUSION: Based on the in vitro tests, AT5, AT6, AT7 and AT8 are considered bioequivalent and interchangeable, while AT2, AT3 and AT4 are considered bioequivalent and interchangeable with the innovator brand (AT9). AT1 has very low dissolution rate, which will likely result in poor bioavailability. The results show the need for constant monitoring of new brands of artesunate introduced into the drug market to ascertain bioequivalence and conformity with pharmacopoeia standards.

Perfil de dissolução in vitro de comprimidos de primaquina disponíveis para tratamento de malária no Brasil / In vitro dissolution profile of primaquine tablets available for malaria treatment in Brazil

A ineficácia clínica de muitos medicamentos tem servido de alerta para estudos mais profundos sobre os componentes da formulação, processos empregados e características físico-químicas dos fármacos. O objetivo deste trabalho foi avaliar a liberação in vitro de comprimidos de fosfato de primaquina disponíveis no Brasil para tratamento da malária, e o desenvolvimento de novas formulações de liberação convencional. Embora os comprimidos de fosfato de primaquina estudados tenham sido aprovados pelos critérios propostos pela Farmacopéia Americana (2006) para o teste de dissolução, não apresentaram desempenho adequado para o perfil de dissolução, mostrando retenção do fármaco durante a liberação. Os resultados indicam a existência de problemas nos comprimidos de fosfato de primaquina analisados, podendo sugerir como um dos fatores responsáveis pelo aparecimento de resistência dos parasitas.

The clinical inefficacy of many medications has served to highlight the need for deeper studies on the formulation components, processes used and physicochemical characteristics of drugs. The objective of this study was to evaluate the in vitro release of primaquine phosphate from tablets available in Brazil for treating malaria, and the development of new formulations for conventional release. Although the primaquine phosphate tablets studied had been approved according to the criteria proposed by the United States Pharmacopoeia (2006) for the dissolution test, they did not present adequate dissolution performance characteristics, in that there was drug retention during the release process. The results indicate the existence of problems in the primaquine phosphate tablets analyzed, and it may suggest that this is one of the factors responsible for the appearance of parasite resistance.

Febrifugine derivative antimalarial activity: quantum mechanical predictors / Descritores da atividade antimalarial de derivados de febrifugina obtidos via mecânica qüântica

Plasmodium falciparum resistant strain development has encouraged the search for new antimalarial drugs. Febrifugine is a natural substance with high activity against P. falciparum presenting strong emetic property and liver toxicity, which prevent it from being used as a clinical drug. The search for analogues that could have a better clinical performance is a current topic. We aim to investigate the theoretical electronic structure by means of febrifugine derivative family semi-empirical molecular orbital calculations, seeking the electronic indexes that could help the design of new efficient derivatives. The theoretical results show there is a clustering in well-defined ranges of several electronic indexes of the most selective molecules. The model proposed for achieving high selectivity was tested with success.

O desenvolvimento de linhagens resistentes de Plasmodium falciparum tem encorajado a busca por novas drogas antimalariais. A febrifugina é uma substância natural com alta atividade contra o P. falciparum que apresenta propriedade emética e toxicidade para o fígado tal que não permitem o seu uso clínico. A busca por análogos que possam ter uma performance clínica melhor é um tema de pesquisa atual. Nosso objetivo é investigar a estrutura eletrônica teórica de uma família de derivados da febrifugina empregando cálculos semi-empíricos de orbitais moleculares, procurando por índices eletrônicos que possam ajudar a modelar novos derivados mais eficientes. Os resultados teóricos mostram que para as moléculas mais seletivas existe um agrupamento dos valores de determinados índices em intervalos bem definidos. O modelo proposto para se obter alta seletividade foi testado com sucesso.

Antimalarial activity of thiophenyl- and benzenesulfonyl-dihydroartemisinin

Each diastereomer of 10-thiophenyl- and 10-benzenesulfonyl-dihydroartemisinin was synthesized from artemisinin in three steps, and screened against chloroquine-resistance and chloroquine-sensitive Plasmodium falciparum. Three of the four tested compounds were found to be effective. Especially, 10 beta-benzenesulfonyl-dihydroartemisinin showed stronger antimalarial activity than artemisinin.

The search for new antimalarial drugs from plants used to treat fever and malaria or plants ramdomly selected: a review

In this review we discuss the ongoing situation of human malaria in the Brazilian Amazon, where it is endemic causing over 610,000 new acute cases yearly, a number which is on the increase. This is partly a result of drug resistant parasites and new antimalarial drugs are urgently needed. The approaches we have used in the search of new drugs during decades are now reviewed and include ethnopharmocology, plants randomly selected, extracts or isolated substances from plants shown to be active against the blood stage parasites in our previous studies. Emphasis is given on the medicinal plant Bidens pilosa, proven to be active against the parasite blood stages in tests using freshly prepared plant extracts. The anti-sporozoite activity of one plant used in the Brazilian endemic area to prevent malaria is also described, the so called "Indian beer" (Ampelozizyphus amazonicus, Rhamnaceae). Freshly prepared extracts from the roots of this plant were totally inactive against blood stage parasites, but active against sporozoites of Plasmodium gallinaceum or the primary exoerythrocytic stages reducing tissue parasitism in inoculated chickens. This result will be of practical importance if confirmed in mammalian malaria. Problems and perspectives in the search for antimalarial drugs are discussed as well as the toxicological and clinical trials to validate some of the active plants for public health use in Brazil

Imunossupressäo induzida pela malária: existe um papel para o óxido nítrico? / Malaria induced immunosuppression: is there a role to nitric oxide?

Objetivo: abordar a hipótese de que a imunossupressäoassociada à malária seja causada por produçäo macrofágica de óxido nítrico. Métodos: revisäo de literatura pertinente. Resultados: uma série de estudos demonstra falha da imunidade celular em animais experimentais e humanos parasitados por Plasmodium. Foi recentemente observado que a ativaçäo crönica de macrófagos induz biossíntese de óxido nítrico, o qual inibe a ribonucleotídeo redutase linfocitária e consequentemente, a proliferaçäo desse tipo celular. O aumento na produçäo de óxido nítrico e a proliferaçäo reduzida de linfócitos estäo bem documentadas em pacientes contaminados por Plasmodium. Conclusöes: a ativaçäo crônica de células mononucleares humanas, como ocorre na malária, provoca secreçäo de óxido nítrico, o que provavelmente, seja a base de funcionamento dos macrófagos supressores. O óxido nítrico inibe a ribonucleotídeo redutase da célula-alvo, nesse caso o linfócito, impedindo sua proliferaçäo. Embora dados definitivos ainda näo estejam disponíveis, esse parece ser o mecanismo da imunossupressäo associada à malária.

Overview: clinical pharmacology of antimalarials.

The effectiveness of antimalarials depends on its pharmacodynamics ie inhibitory effect on the parasites and unwanted effects on the host. It also depends on the pharmacokinetics of the drugs. The ideal antimalarials are drugs that show curative activity in the absence of toxicity to the host. Recommendation for antimalarial dosage regimens should be based on pharmacokinetic and pharmacodynamic studies in appropriate populations ie ethnic groups, adults children, and in pregnancy. Chloroquine remains the drug of choice for treating malaria caused by Plasmodium species other than P. falciparum. Even in the presence of chloroquine resistance the drug may still be quite useful, especially in areas with high communal immunity. In general sulfadoxine/pyrimethamine (S/P) should be used as an alternative antimalarial when chloroquine fails. The decision to change to S/P from chloroquine depends on many factors. Quinine still remains the drug of choice for severe chloroquine-resistant falciparum malaria. Resistance to mefloquine has appeared the exact mechanism being unknown. In general, before the use of any combination of antimalarial drugs the superiority (efficacy and side-effects) over each of the individual drugs should be clearly demonstrated. The combination of mefloquine with sulfadoxine/pyrimethamine was made on the grounds that the combination would delay the resistance to mefloquine. Desferrioxamine will hardly be an agent to be used on its own for treating malaria due to the high recrudescent rate. However, a recent report indicated that its association with antimalarial drugs in the management of severe and complicated falciparum malaria shortens fever and parasite clearance time and resolves complications faster than the standard antimalarial drug alone. Clinical trials with halofantrine has been done in several countries in the region from 1988 to the present with diverse results. Further studies on a larger scale should be carried out to ascertain whether these are due to variation in drug absorption or drug resistance. An improved formulation of halofantrine must be developed to ensure adequate absorption and bioavailability. The artermisinin group of antimalarials is known to be highly effective and independent, in its mode of action, from standard malaria drugs but associated with high recrudescent rate. Phase II studies are needed for determining/optimizing therapeutic dose regimens and to ensure safer and more effective use of these compounds.