New Insights into the Mechanism of Action of the Drug Chloroquine: Direct Interaction with DNA and Cytotoxicity.

Chloroquine (CLQ) and hydroxychloroquine (HCLQ) are compounds largely employed in the treatment of various human diseases for decades. Nevertheless, a number of intrinsic details concerning their mechanisms of action, especially at the molecular level, are still unknown or have presented controversial results in the literature. Using optical tweezers, here, we investigate at the single-molecule level the molecular mechanism of action of the drug CLQ in its intrinsic interaction with the double-stranded (ds)DNA molecule, one of its targets inside cells, determining the binding modes and the physicochemical (binding) parameters of the interaction. In particular, we show that the ionic strength of the surrounding medium strongly influences such interaction, changing even the main binding mode. In addition, the cytotoxicity of CLQ against three different cell lines was also investigated here, allowing one to evaluate and compare the effect of the drug on the cell viability. In particular, we show that CLQ is highly cytotoxic at a very low (a few micromolar) concentration range for all cell lines tested. These results were rigorously compared to the equivalent ones obtained for the closely related compound hydroxychloroquine (HCLQ), allowing a critical comparison between the action of these drugs at the molecular and cellular levels.

Unveiling the Molecular Structure of Antimalarial Drugs Chloroquine and Hydroxychloroquine in Solution through Analysis of 1H NMR Chemical Shifts.

Chloroquine (CQ) and hydroxychloroquine (HCQ) have been standard antimalarial drugs since the early 1950s, and very recently, the possibility of their use for the treatment of COVID-19 patients has been considered. To understand the drug mode of action at the submicroscopic level (atoms and molecules), molecular modeling studies with the aid of computational chemistry methods have been of great help. A fundamental step in such theoretical investigations is the knowledge of the predominant drug molecular structure in solution, which is the real environment for the interaction with biological targets. Our strategy to access this valuable information is to perform density functional theory (DFT) calculations of 1H NMR chemical shifts for several plausible molecular conformers and then find the best match with experimental NMR profile in solution (since it is extremely sensitive to conformational changes). Through this procedure, after optimizing 30 trial distinct molecular structures (ωB97x-D/6-31G(d,p)-PCM level of calculation), which may be considered representative conformations, we concluded that the global minimum (named M24), stabilized by an intramolecular N-H hydrogen bond, is not likely to be observed in water, chloroform, and dimethyl sulfoxide (DMSO) solution. Among fully optimized conformations (named M1 to M30, and MD1 and MD2), we found M12 (having no intramolecular H-bond) as the most probable structure of CQ and HCQ in water solution, which is a good approximate starting geometry in drug-receptor interaction simulations. On the other hand, the preferred CQ and HCQ structure in chloroform (and CQ in DMSO-d6) solution was assigned as M8, showing the solvent effects on conformational preferences. We believe that the analysis of 1H NMR data in solution can establish the connection between the macro level (experimental) and the sub-micro level (theoretical), which is not so apparent to us and appears to be more appropriate than the thermodynamic stability criterion in conformational analysis studies.

HPLC methods for choloroquine determination in biological samples and pharmaceutical products.

OBJECTIVE: Review and assess pharmaceutical and clinical characteristics of chloroquine including high-performance liquid chromatography (HPLC)-based methods used to quantify the drug in pharmaceutical products and biological samples. EVIDENCE ACQUISITION: A literature review was undertaken on the PubMed, Science Direct, and Scielo databases using the following keywords related to the investigated subject: 'chloroquine', 'analytical methods', and 'HPLC'. RESULTS: For more than seven decades, chloroquine has been used to treat malaria and some autoimmune diseases, such as lupus erythematosus and rheumatoid arthritis. There is growing interest in chloroquine as a therapeutic alternative in the treatment of HIV, Q fever, Whipple's disease, fungal, Zika, Chikungunya infections, Sjogren's syndrome, porphyria, chronic ulcerative stomatitis, polymorphic light eruption, and different types of cancer. HPLC coupled to UV detectors is the most employed method to quantify chloroquine in pharmaceutical products and biological samples. The main chromatographic conditions used to identify and quantify chloroquine from tablets and injections, degradation products, and metabolites are presented and discussed. CONCLUSION: Research findings reported in this article may facilitate the repositioning, quality control, and biological monitoring of chloroquine in modern pharmaceutical dosage forms and treatments.

A Novel Hybrid of Chloroquine and Primaquine Linked by Gold(I): Multitarget and Multiphase Antiplasmodial Agent.

Plasmodium parasites kill 435 000 people around the world every year due to unavailable vaccines, a limited arsenal of antimalarial drugs, delayed treatment, and the reduced clinical effectiveness of current practices caused by drug resistance. Therefore, there is an urgent need to discover and develop new antiplasmodial candidates. In this work, we present a novel strategy to develop a multitarget metallic hybrid antimalarial agent with possible dual efficacy in both sexual and asexual erythrocytic stages. A hybrid of antimalarial drugs (chloroquine and primaquine) linked by gold(I) was synthesized and characterized by spectroscopic and analytical techniques. The CQPQ-gold(I) hybrid molecule affects essential parasite targets, it inhibits ß-hematin formation and interacts moderately with the DNA minor groove. Its interaction with PfTrxR was also examined in computational modeling studies. The CQPQ-gold(I) hybrid displayed an excellent in vitro antimalarial activity against the blood-stage of Plasmodium falciparum and liver-stage of Plasmodium berghei and efficacy in vivo against P. berghei, thereby demonstrating its multiple-stage antiplasmodial activity. This metallic hybrid is a promising chemotherapeutic agent that could act in the treatment, prevention, and transmission of malaria.

Chloroquine as a promising adjuvant therapy for type 1 Diabetes Mellitus.

Chloroquine (CQ) and hydroxychloroquine, are promising anti-inflammatory drugs for the treatment of Diabetes mellitus (DM) to prevent associated complications. Therefore, this study evaluated the anti-inflammatory effects of CQ-free and CQ-incorporated polylactic acid nanoparticles (NPs) in the peripheral blood mononuclear cells (PBMCs) of patients with type 1 Diabetes mellitus (T1DM). In total, 25 normoglycemic individuals and 25 patients with T1DM aged 10-16 years were selected and glycemic controls evaluated. After cell viability assessed by MTT assay, T1DM PBMCs were subjected to a CQ concentration of 10 µM in three different conditions: not treated (NT), treated with CQ, and treated with CQ NPs. The cells were incubated for 48 h, and the mRNA expressions of cytokines IL1B, IFNG, TNFA, IL12, and IL10 were determined by relative quantification through real-time PCR at 24 h intervals. IL1B expression decreased in CQ and CQ NP-treated cells after 48 h (p < 0.001) and 24 h (p < 0.05) of treatment, respectively. IFNG and IL12 expressions significantly decreased (p < 0.001) in cells treated with CQ and CQ NPs at 24 and 48 h compared to NT. TNFA and IL10 expressions significantly decreased after 48 h (p < 0.001) and 24 h (p < 0.002), respectively, by both CQ and CQ NPs treatment. Despite being a preliminary in vitro study, CQ has anti-inflammatory activity in the primary cells of T1DM patients and could represent an alternative and adjuvant anti-inflammatory therapy to prevent diabetes complications.

Interactions Between Remdesivir, Ribavirin, Favipiravir, Galidesivir, Hydroxychloroquine and Chloroquine with Fragment Molecular of the COVID-19 Main Protease with Inhibitor N3 Complex (PDB ID:6LU7) Using Molecular Docking.

We started a study on the molecular docking of six potential pharmacologically active inhibitors compounds that can be used clinically against the COVID-19 virus, in this case, remdesivir, ribavirin, favipiravir, galidesivir, hydroxychloroquine and chloroquine interacting with the main COVID-19 protease in complex with a COVID-19 N3 protease inhibitor. The highest values of affinity energy found in order from highest to lowest were chloroquine (CHL), hydroxychloroquine (HYC), favipiravir (FAV), galidesivir (GAL), remdesivir (REM) and ribavirin (RIB). The possible formation of hydrogen bonds, associations through London forces and permanent electric dipole were analyzed. The values of affinity energy obtained for the hydroxychloroquine ligands was -9.9 kcal/mol and for the chloroquine of -10.8 kcal/mol which indicate that the coupling contributes to an effective improvement of the affinity energies with the protease. Indicating that, the position chosen to make the substitutions may be a pharmacophoric group, and cause changes in the protease.

Chloroquine and Sulfadoxine Derivatives Inhibit ZIKV Replication in Cervical Cells.

Despite the severe morbidity caused by Zika fever, its specific treatment is still a challenge for public health. Several research groups have investigated the drug repurposing of chloroquine. However, the highly toxic side effect induced by chloroquine paves the way for the improvement of this drug for use in Zika fever clinics. Our aim is to evaluate the anti-Zika virus (ZIKV) effect of hybrid compounds derived from chloroquine and sulfadoxine antimalarial drugs. The antiviral activity of hybrid compounds (C-Sd1 to C-Sd7) was assessed in an in-vitro model of human cervical and Vero cell lines infected with a Brazilian (BR) ZIKV strain. First, we evaluated the cytotoxic effect on cultures treated with up to 200 µM of C-Sds and observed CC50 values that ranged from 112.0 ± 1.8 to >200 µM in cervical cells and 43.2 ± 0.4 to 143.0 ± 1.3 µM in Vero cells. Then, the cultures were ZIKV-infected and treated with up to 25 µM of C-Sds for 48 h. The treatment of cervical cells with C-Sds at 12 µM induced a reduction of 79.8% ± 4.2% to 90.7% ± 1.5% of ZIKV-envelope glycoprotein expression in infected cells as compared to 36.8% ± 2.9% of infection in vehicle control. The viral load was also investigated and revealed a reduction of 2- to 3-logs of ZIKV genome copies/mL in culture supernatants compared to 6.7 ± 0.7 × 108 copies/mL in vehicle control. The dose-response curve by plaque-forming reduction (PFR) in cervical cells revealed a potent dose-dependent activity of C-Sds in inhibiting ZIKV replication, with PFR above 50% and 90% at 6 and 12 µM, respectively, while 25 µM inhibited 100% of viral progeny. The treatment of Vero cells at 12 µM led to 100% PFR, confirming the C-Sds activity in another cell type. Regarding effective concentration in cervical cells, the EC50 values ranged from 3.2 ± 0.1 to 5.0 ± 0.2 µM, and the EC90 values ranged from 7.2 ± 0.1 to 11.6 ± 0.1 µM, with selectivity index above 40 for most C-Sds, showing a good therapeutic window. Here, our aim is to investigate the anti-ZIKV activity of new hybrid compounds that show highly potent efficacy as inhibitors of ZIKV in-vitro infection. However, further studies will be needed to investigate whether these new chemical structures can lead to the improvement of chloroquine antiviral activity.

Chirobiotic V Versus Chiralpak ID for the Enantioselective Chromatographic Separation of Chloroquine: Stability and Validation Study.

Chloroquine is a chiral antimalarial drug and demonstrates enantioselective pharmacodynamic and pharmacokinetic properties. However, this drug is administered as racemate. The knowledge of stereoselective aspects of these agents may be useful to better understand their mechanisms of action and to optimize their safety and/or clinical efficacy. In this study, an enantioselective analytical method for the quantification of chloroquine enantiomers was developed using HPLC-UV. The chromatographic conditions were: Chirobiotic V column (100 × 2.1 mm, 5 µm) at 25°C, mobile phase containing methanol:acetic acid:triethylamine (100:0.12:0.12), flow rate 1 mL/min, injection volume 10 µL and detection at 258 nm. The validation parameters evaluated were selectivity, linearity, precision, accuracy, and robustness. In addition, a stability study after forced degradation of chloroquine enantiomers was performed. The enantioseparation of chloroquine using a polysaccharide-based chiral stationary phase (Chiralpak ID) at different mobile phase composition was evaluated and the chromatographic performance of both columns was compared. Thus, a stability-indicating chiral analytical method was developed and fully validated, allowing the separation of chloroquine enantiomers and its degradation products in tablets available in Brazil.

Chloroquine analogs as antimalarial candidates with potent in vitro and in vivo activity.

In spite of recent efforts to eradicate malaria in the world, this parasitic disease is still considered a major public health problem, with a total of 216 million cases of malaria and 445,000 deaths in 2016. Artemisinin-based combination therapies remain effective in most parts of the world, but recent cases of resistance in Southeast Asia have urged for novel approaches to treat malaria caused by Plasmodium falciparum. In this work, we present chloroquine analogs that exhibited high activity against sensitive and chloroquine-resistant P. falciparum blood parasites and were also active against P. berghei infected mice. Among the compounds tested, DAQ, a chloroquine analog with a more linear side chain, was shown to be the most active in vitro and in vivo, with low cytotoxicity, and therefore may serve as the basis for the development of more effective chloroquine analogs to aid malaria eradication.

Optimization of antimalarial, and anticancer activities of (E)-methyl 2-(7-chloroquinolin-4-ylthio)-3-(4-hydroxyphenyl) acrylate.

Chemically modified versions of bioactive substances, are particularly useful in overcoming barriers associated with drug formulation, drug delivery and poor pharmacokinetic properties. In this study, a series of fourteen (E)-methyl 2-(7-chloroquinolin-4-ylthio)-3-(4-hydroxyphenyl) acrylate (2-15) were prepared by using a one step synthesis from 1 previously described by us as potential antimalarial and antitumor agent. Molecules were evaluated as inhibitors of ß-hematin formation, where most of them showed a significant inhibition value (% > 70). The best inhibitors were tested in vivo as potential antimalarials in mice infected with P. berghei ANKA, chloroquine susceptible strain. Three of them (5, 6, and 15) displayed antimalarial activity comparable to that of chloroquine. Also, molecules were evaluated for their cytotoxic activity against two human cancer cell lines (Jurkat E6.1 and HL60) and primary culture of human lymphocytes. Most of the synthesized compounds, except for analogs 2-6, 8, and 10-12, displayed cytotoxicity against cancer cell lines without affecting normal cells. The potency of the compounds was 15 ≫ 1, and 14 > 7, 9, and 13. Flow cytometry analysis demonstrated an increase in apoptotic cell death after 24 h. The compounds may affect tumor cell autophagy and consequently increase cell apoptosis.

Platinum(ii)-chloroquine complexes are antimalarial agents against blood and liver stages by impairing mitochondrial function.

Chloroquine is an antimalarial agent with strong activity against the blood stage of Plasmodium infection, but with low activity against the parasite's liver stage. In addition, the resistance to chloroquine limits its clinical use. The discovery of new molecules possessing multistage activity and overcoming drug resistance is needed. One possible strategy to achieve this lies in combining antimalarial quinolones with the pharmacological effects of transition metals. We investigated the antimalarial activity of four platinum(ii) complexes composed of chloroquine and phosphine ligands, denoted as WV-90, WV-92, WV-93 and WV-94. In comparison with chloroquine, the complexes were less potent against the chloroquine-sensitive 3D7 strain but they were as active as chloroquine in inhibiting the chloroquine-resistant W2 strain of P. falciparum. Regarding selectivity, the complexes WV-90 and WV-93 displayed higher indexes. Unlike chloroquine, the complexes act as irreversible parasiticidal agents against trophozoites and the WV-93 complex displayed activity against the hepatic stage of P. berghei. The in vivo suppression activity against P. berghei in the Peters 4 day test displayed by the complexes was similar to that of chloroquine. However, the efficacy in an established P. berghei infection in the Thompson test was superior for the WV-93 complex compared to chloroquine. The complexes' antimalarial mechanism of action is initiated by inhibiting the hemozoin formation. While chloroquine efficiently inhibits hemozoin, parasites treated with the platinum complexes display residual hemozoin crystals. This is explained since the interaction of the platinum complexes with ferriprotoporphyrin is weaker than that of chloroquine. However, the complexes caused a loss of mitochondrial integrity and subsequent reduction in mitochondrial activity, and their effects on mitochondria were more pronounced than those in the chloroquine-treated parasites. The dual effect of the platinum complexes may explain their activity against the hemozoin-lacking parasites (hepatic stage), where chloroquine has no activity. Our findings indicate that the platinum(ii)-chloroquine complexes are multifunctional antimalarial compounds and reinforce the importance of metal complexes in antimalarial drug discovery.

N-(2-(arylmethylimino)ethyl)-7-chloroquinolin-4-amine derivatives, synthesized by thermal and ultrasonic means, are endowed with anti-Zika virus activity.

Zika virus (ZIKV), an emerging Flavivirus, was recently associated with severe neurological complications and congenital diseases. Therefore, development of antiviral agents capable of inhibiting ZIKV replication is urgent. Chloroquine is a molecule with a confirmed safety history for use with pregnant women, and has been found to exhibit anti-ZIKV activity at concentrations around 10 µM. This suggests that modifications to the chloroquine structure could be promising for obtaining more effective anti-ZIKV agents. Here, we report the ability of a series of N-(2-(arylmethylimino)ethyl)-7-chloroquinolin-4-amine derivatives to inhibit ZIKV replication in vitro. We have found that the quinoline derivative, N-(2-((5-nitrofuran-2-yl)methylimino)ethyl)-7-chloroquinolin-4-amine, 40, was the most potent compound within this series, reducing ZIKV replication by 72% at 10 µM. Compound 40 exhibits an EC50 value of 0.8 ± 0.07 µM, compared to that of chloroquine of 12 ± 3.2 µM. Good activities were also obtained for other compounds, including those with aryl groups = phenyl, 4-fluorophenyl, 4-nitrophenyl, 2,6-dimethoxyphenyl, 3-pyridinyl and 5-nitrothien-2-yl. Syntheses of these quinoline derivatives have been obtained both by thermal and ultrasonic means. The ultrasonic method produced comparable yields to the thermal (reflux) method in very much shorter times 30-180 s compared to 30-180 min reactions times. These results indicate that this group of compounds is a good follow-up point for the potential discovery of new drugs against the Zika disease.

Chiral Platinum(II) Complexes Featuring Phosphine and Chloroquine Ligands as Cytotoxic and Monofunctional DNA-Binding Agents.

Chiral molecules in nature are involved in many biological events; their selectivity and specificity make them of great interest for understanding the behavior of bioactive molecules, by providing information about the chiral discrimination. Inspired by these conformational properties, we present the design and synthesis of novel chiral platinum(II) complexes featuring phosphine and chloroquine ligands with the general formula [PtCl(P)2(CQ)]PF6 (where (P)2 = triphenylphosphine (PPh3) (5), 1,3-bis(diphenylphosphine)propane (dppp) (6), 1,4-bis(diphenylphosphine)butane (dppb) (7), 1,1'-bis(diphenylphosphine)ferrocene (dppf) (8), and CQ = chloroquine] and their precursors of the type [PtCl2(P)2] are described. The complexes were characterized by elemental analysis, absorption spectroscopy in the infrared and ultraviolet-visible (UV-vis) regions, multinuclear ((1)H, (13)C, (31)P, (15)N, and (195)Pt) NMR spectroscopy, cyclic voltammetry, and mass spectrometry (in the case of chloroquine complexes). The interactions of the new platinum-chloroquine complexes with both albumin (BSA), using fluorescence spectroscopy, and DNA, by four widely reported methods were also evaluated. These experiments showed that these Pt-CQ complexes interact strongly with DNA and have high affinities for BSA, in contrast to CQ and CQDP (chloroquine diphosphate), which interact weakly with these biomolecules. Additional assays were performed in order to investigate the cytotoxicity of the platinum complexes against two healthy cell lines (mouse fibroblasts (L929) and the Chinese hamster lung (V79-4)) and four tumor cell lines (human breast (MDA-MB-231 and MCF-7), human lung (A549), and human prostate (DU-145)). The results suggest that the Pt-CQ complexes are generally more cytotoxic than the free CQ, showing that they are promising as anticancer drugs.

Antiplasmodial activity of synthetic ellipticine derivatives and an isolated analog.

Ellipticine has been shown previously to exhibit excellent in vitro antiplasmodial activity and in vivo antimalarial properties that are comparable to those of the control drug chloroquine in a mouse malaria model. Ellipticine derivatives and analogs exhibit antimalarial potential however only a few have been studied to date. Herein, ellipticine and a structural analog were isolated from Aspidosperma vargasii bark. A-ring brominated and nitrated ellipticine derivatives exhibit good in vitro inhibition of Plasmodium falciparum K1 and 3D7 strains. Several of the compounds were found not to be toxic to human fetal lung fibroblasts. 9-Nitroellipticine (IC50=0.55µM) exhibits greater antiplasmodial activity than ellipticine. These results are further evidence of the antimalarial potential of ellipticine derivatives.

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.

Synthesis, characterization and biological activity of trans-platinum(II) complexes with chloroquine.

Three platinum-chloroquine complexes, trans-Pt(CQDP)(2)(I)(2) [1], trans-Pt(CQDP)(2)(Cl)(2) [2] and trans-Pt(CQ)(2)(Cl)(2) [3], were prepared and their most probable structure was established through a combination of spectroscopic analysis and density functional theory (DFT) calculations. Their interaction with DNA was studied and their activity against 6 tumor cell lines was evaluated. Compounds 1 and 2 interact with DNA primarily through electrostatic contacts and hydrogen bonding, with a minor contribution of a covalent interaction, while compound 3 binds to DNA predominantly in a covalent fashion, with weaker secondary electrostatic interactions and possibly hydrogen bonding, this complex also exerted greater cytotoxic activity against the tumor cell lines.

Synthesis and antimalarial activity of new heterocyclic hybrids based on chloroquine and thiazolidinone scaffolds.

A series of new 21 chloroquine heterocyclic hybrids containing either benzylamino fragment or N-(aminoalkyl)thiazolidin-4-one moiety were synthesized and screened for their antimalarial activity against chloroquine (CQ)-sensitive 3D7 and multidrug-resistance Dd2 strains of Plasmodium falciparum. Although no compounds more active than CQ against 3D7 was found; against Dd2 strain, six compounds, four of them with benzylamino fragment, showed an excellent activity, up to 3-fold more active than CQ. Non specific cytotoxicity on J774 macrophages was observed in some compounds whereas only two of them showed liver toxicity on HepG2 cells. In addition, all active compounds inhibited the ferriprotoporphyrin IX biocrystalization process in concentrations around to CQ. In vivo preliminary results have shown that at least two compounds are as active as CQ against Plasmodium berghei ANKA.

The mechanism of antimalarial action of [Au(CQ)(PPh(3))]PF(6): structural effects and increased drug lipophilicity enhance heme aggregation inhibition at lipid/water interfaces.

The mechanism of antimalarial action of [Au(CQ)(PPh(3))]PF(6) (1), which is active in vitro against CQ-resistant P. falciparum and in vivo against P. berghei, has been investigated in relation to hemozoin formation and DNA as possible important targets. Complex 1 interacts with heme and inhibits ß-hematin formation both in aqueous medium and near water/n-octanol interfaces at pH ~5 to a greater extent than chloroquine diphosphate (CQDP) or other known metal-based antimalarial agents; the higher inhibition activity is probably related to the higher lipophilicity observed for 1 through partition coefficient measurements at low pH, with respect to CQDP. The interactions of complex 1 with DNA were explored using spectrophotometric and fluorimetric titrations, circular dichroism spectroscopy, viscosity and melting point studies, as well as electrophoresis and covalent binding assays. The experimental data indicate that complex 1 interacts with DNA predominantly by intercalation and electrostatic association of the CQ moiety, similarly to free CQDP, while no covalent metal-DNA binding seems to take place. The most likely antimalarial mechanism for complex 1 is thus heme aggregation inhibition; the high activities observed against resistant parasites are probably due to the structural modification of CQ introduced by the presence of the gold-triphenylphosphine fragment, together with the enhanced lipophilic character.

Molecular modeling and UV-vis spectroscopic studies on the mechanism of action of reversed chloroquine (RCQ).

Reversed chloroquine (RCQ) is a multiple ligand compound active against chloroquine-sensitive and resistant falciparum malaria. It is composed by a 4-aminoquinoline moiety (like that present in chloroquine (CQ)) joined to imipramine (IMP), a modulating agent that also showed intrinsic antiplasmodial activity against Brazilian Plasmodium falciparum isolates resistant to CQ. Molecular modeling and ultraviolet-visible spectroscopy (UV-vis) studies strongly suggest that the interaction between RCQ and heme is predominant through the quinoline moiety in a mechanism of action similar to that observed for CQ.

Thiopurine derivatives containing triazole and steroid: synthesis, antimalarial and antileishmanial activities.

A series of novel 6-thiopurine derivates containing 1,2,3-triazole were synthesized and their in vivo antimalarial activity and in vitro antileishmanial activity were examined. The compounds 10, 11, 12 and 14 presented higher values of inhibition of parasite multiplication than chloroquine. For antileishmanial activity, the compound 14 showed activity against the three species of Leishmania tested. None of compounds showed cytotoxicity against mammalian cells.