Giovanny Garavito

Aryl piperazine and pyrrolidine as antimalarial agents. Synthesis and investigation of structure-activity relationships

Piperazine and pyrrolidine derivatives were synthesised and evaluated for their capacity to inhibit the growth of Plasmodium falciparum chloroquine-resistant (FCR-3) strain in culture. The combined presence of a hydroxyl group, a propane chain and a fluor were shown to be crucial for the antiplasmodial activity. Five compounds of the aryl-alcohol series inhibited 50% of parasite growth at doses ≤10 μM. The most active compound 1-(4-fluoronaphthyl)-3-[4-(4-nitro-2-trifluoromethylphenyl)piperazin-1-yl] propan-1-ol was almost 20-40 times more active on P. falciparum (IC(50): 0.5 μM) than on tumorogenic and non-tumorogenic cells. In vivo it has a very weak effect; inhibiting 35% of parasite growth only, at 10 mg/kg/day against Plasmodium berghei infected mice without any impact on survival time. In silico molecular docking study and molecular electrostatic potential calculation revealed that this compound bound to the active site of Plasmodium plasmepsin II enzyme.

The in vivo antimalarial activity of methylene blue combined with pyrimethamine, chloroquine and quinine

The effectiveness of methylene blue (MB) combined with pyrimethamine (PYR), chloroquine (CQ) or quinine (Q) was examined in a classical four-day suppressive test against a causative agent of rodent malaria, Plasmodium berghei. A marked potentiation was observed when MB was administered at a non-curative dose of 15 mg/kg/day in combination with PYR (0.19 mg/kg/day) or Q (25 mg/kg/day). No synergy was found between MB (15 mg/Kg) and CQ (0.75 mg/Kg). Our results suggest that the combination of MB with PYR or Q may improve the efficacy of these currently used antimalarial drugs.

Exploring the scope of new arylamino alcohol derivatives: Synthesis, antimalarial evaluation, toxicological studies, and target exploration

Synthesis of new 1-aryl-3-substituted propanol derivatives followed by structure-activity relationship, in silico drug-likeness, cytotoxicity, genotoxicity, in silico metabolism, in silico pharmacophore modeling, and in vivo studies led to the identification of compounds 22 and 23 with significant in vitro antiplasmodial activity against drug sensitive (D6 IC50 ≤ 0.19 μM) and multidrug resistant (FCR-3 IC50 ≤ 0.40 μM and C235 IC50 ≤ 0.28 μM) strains of Plasmodium falciparum. Adequate selectivity index and absence of genotoxicity was also observed. Notably, compound 22 displays excellent parasitemia reduction (98 ± 1%), and complete cure with all treated mice surviving through the entire period with no signs of toxicity. One important factor is the agreement between in vitro potency and in vivo studies. Target exploration was performed; this chemotype series exhibits an alternative antimalarial mechanism.

Revisión documental de los productos naturales legalmente autorizados para su mercadeo en Colombia

Introducción: El grupo de los productos naturales ha cobrado gran interés en los últimos años debido a la creencia popular que son eficaces y más seguros que los medicamentos de síntesis o por recientes tendencias en salud que buscan suplementar la alimentación. Objetivo: Describir el grupo de los productos naturales desde el punto de vista de la autoridad sanitaria. Metodología: Estudio observacional descriptivo de corte transversal a partir del universo de los Registros Sanitarios de Productos Naturales que presenta la base de datos del Instituto Nacional de Vigilancia de Medicamentos y Alimentos (Autoridad Sanitaria Colombiana). Resultados: Aproximadamente la mitad de los productos naturales legalmente aceptados para su mercadeo son productos fitoterapéuticos y la otra mitad la componen los suplementos dietarios junto con los productos de uso específico. La especie vegetal con mayor número de autorizaciones de comercialización es la alcachofa (Cynara scolymus), seguida de caléndula (Calendula officinalis), valeriana (Valeriana officinalis), ajo (Allium sativum) y ginkgo (Ginkgo biloba). Hay un predominio del empleo de especies foráneas en los productos fitoterapéuticos comercializados. Se propone una clasificación novedosa del órgano de la planta o droga empleado en la producción con la cual es evidente el mayor uso de las hojas respecto a cualquier otro órgano. Cápsulas, tabletas y soluciones son las formas farmacéuticas predominantes. Conclusiones: El grupo de productos naturales ha presentado una evolución creciente en registro durante los últimos años; en el subgrupo de los productos fitoterapéuticos predomina la fabricación nacional aun cuando es mínimo el empleo de especies nativas, mientras que para los suplementos dietarios y productos de uso específico es mayor la importación, lo que evidencia la necesidad de una política nacional que articule la generación de normatividad con las necesidades colombianas y logre estimular la valorización y uso sostenible de nuestros recursos naturales con un retorno adecuado a las comunidades que se refleje en una mayor producción local y el empleo de recursos en los que hay ventajas competitivas.

In Vitro Susceptibility of Plasmodium vivax to Antimalarials in Colombia

ABSTRACT The in vitro susceptibilities of 30 isolates of Plasmodium vivax to a number of antimalarials (chloroquine [CQ], mefloquine, amodiaquine, quinine, and artesunate [AS]) were evaluated. The isolates came from the region of Urabá in Colombia, in which malaria is endemic, and were evaluated by the schizont maturation test. The 50% inhibitory concentration (IC50) was 0.6 nM (95% confidence interval [CI], 0.3 to 1.0 nM) for artesunate, 8.5 nM (95% CI, 5.6 to 13.0 nM) for amodiaquine, 23.3 nM (95% CI, 12.4 to 44.1 nM) for chloroquine, 55.6 nM (95% CI, 36.8 to 84.1 nM) for mefloquine, and 115.3 nM (95% CI, 57.7 to 230.5 nM) for quinine. The isolates were classified according to whether the initial parasites were mature or immature trophozoites (Tfz). It was found that the IC50s for chloroquine and artesunate were significantly different in the two aforementioned groups (P < 0.001). The IC50s of CQ and AS were higher in the isolates from mature Tfz (CQ, 39.3 nM versus 17 nM; AS, 1.4 nM versus 0.3 nM), and 10% of the isolates showed lower susceptibilities to one of the antimalarial drugs, 13.3% to two antimalarial drugs, and 3.3% to more than three antimalarial drugs. It should be highlighted that despite the extensive use of chloroquine in Colombia, P. vivax continues to be susceptible to antimalarials. This is the first report, to our knowledge, showing in vitro susceptibilities of P. vivax isolates to antimalarials in Colombia.

Pharmacological activity of Curarea toxicofera in combination with classical antimalarial treatments

ETHNOPHARMACOLOGICAL RELEVANCE In the Leticia-Amazonas area, Uitoto indigenous people use a preparation of Curarea toxicofera (Wedd) Barneby & Krukoff (Menispermaceae) alone or combined with prescribed medications to prevent and treat malaria. AIM OF STUDY To determine the in vitro and in vivo antiplasmodial activity of traditional preparations of Curarea toxicofera alone and in combination with classical antimalarials. MATERIAL AND METHODS The traditional preparation was evaluated in vitro against P. falciparum FCR3 CQ resistant strain, alone and combined. The preparation was further administered orally alone or combined with chloroquine and artesunate in mice infected with Plasmodium berghei ANKA strain on the four-day antimalarial test model. RESULTS The herbal remedy used alone was able to significantly decrease the parasitemia both in vitro (IC50 7.3 µg/ml) and in vivo (ED50 328 mg/Kg) but it was less active than chloroquine (IC50 0.29 µg/ml in vitro and ED50 2.3 mg/Kg/day in vivo), and than artesunate (IC50 0.002 µg/ml and ED50 3.7 mg/Kg/day). Interestingly it presented synergism with chloroquine in vitro (Combination Index: 0.39) and in vivo; and was additive with artesunate in vitro (Combination Index: 0.94) and in vivo. CONCLUSION The traditional preparation showed potential as an antimalarial and, when used in combination, does not negatively affect the efficacy of the drugs evaluated. Pre-clinical studies should be conducted with a standardized preparation to confirm its efficacy and safety alone and in combination with chloroquine and artesunate.

Aspidosperma species (Apocynaceae) as sources of antimalarials: from the in vitro antiplasmodial activity of extracts to pre-clinical toxicological studies for the development of efficient and safe antimalarial phytomedicines

We report here our investigations on plants belonging to the botanical genus Aspidosperma (Apocynaceae) that are used to treat malaria and/or fevers in Brazil, aiming to prepare standardized alkaloid extracts for phytomedicines development. Ethanol and alkaloid extracts of A. parvifolium and A. subincanum barks were prepared and their in vitro antiplasmodial activity was evaluated against Plasmodium falciparum (W2 strain) by the pLDH method. Bioguided fractionation of the active alkaloid extracts was undertaken. A study on antiplasmodial activity versus alkaloids content variation from three A. subincanum specimens that were collected in different regions was carried on by HPLC-UV. Ethanol and alkaloid extracts from A. parvifolium and A. subincanum were evaluated in toxicological studies in male and female Swiss mice and male Wistar rats (n = 10); a control group was included in the experiments. At the end of treatment, animals were sacrificed, hematology and serum biochemical analyses were performed. Fractionation of alkaloid extracts from A. parvifolium and A. subincanum guided by in vitro assays against P. falciparum (W2 strain) led to the isolation of the indole alkaloids uleine (Oliveira et al., 2010) and N-demethyluleine. HPLC-UV and LC-UV-MS/ESI analyses of the extracts disclosed uleine as the major constituent, its content reaching 70.7% in the alkaloid extract from A. subincanum (ASALB) which was more potent than uleine and N-demethyluleine themselves in the in vitro assays, as can be inferred from the selectivity indexes in relation to HepG2 cells (SI = CC50/IC50) of ASALB (100), uleine (44) and N-demethyluleine (21). Moreover, a significative variation on the contents of these two alkaloids was observed for the same plant species when collected in different regions (Paula, 2014). Both ethanol and alkaloid extracts from A. parvifolium bark were relatively safe, producing minor changes in the parameters evaluated, especially in smaller doses, thus making feasible their future use in phase I clinical trials. On the other hand, high toxicity of both extracts from A. subincanum bark was observed in doses >200 mg/kg. The present results point to the necessity of rigorous investigation of traditional antimalarial plants including in vitro studies for identification of active natural products, standardization of extracts to be submitted to pre-clinical toxicological studies and controlled clinical trials. Our results disclose that efficient and safe phytomedicines might be developed from standardized crude or semi-purified extracts of Aspidosperma species containing the active chemical entities.