In vitro assessment of 2-acetylpyridine thiosemicarbazones against chloroquine-resistant Plasmodium falciparum

Synthesis, characterization, antibacterial activity of thiosemicarbazones derivatives and their computational approaches: Quantum calculation, molecular docking, molecular dynamic, ADMET, QSAR

The thiosemicarbazones and their derivatives have been recognized as antimicrobial agents against human pathogenic bacteria and fungi. Regarding these prospective, this study was designed to address the new antimicrobial agents from thiosemicarbazones and their derivatives. These derivatives were synthesized by multi-step synthesis methods, such as alkylation, acidification, esterification, and formed the 4-(4'-alkoxybenzoyloxy) thiosemicarbazones and its derivatives (THS1, THS2, THS3, THS4, and THS5). Afterward the synthesis, compounds were characterized by ¹H NMR, FTIR spectra, and melting point. Later, the computational tools were applied to evaluate the drug likeness properties, bioavailability score, Lipinski rule, absorption, distribution, metabolism, excretion, and toxicity (ADMET). Secondly, the quantum calculations, for instance HOMO, LUMO and chemical descriptors, were calculated by the density functional theory (DFT). Finally, the molecular docking was performed against seven human pathogenic bacteria, black fungus (Rhizomucor mieh, Mucor lusitanicus, Mycolicibacterium smegmatis) and white fungus strains (Candida Auris, Aspergillus luchuensis, Candida albicans). To check and validate of molecular docking procedure and stability of docked complex for ligand and protein, the molecular dynamic was performed of docked complex. From the docking score with calculating the binding affinity, these derivatives could show a higher affinity than standard drug against all pathogens. From the computational details, it could be decided to do in-vitro test as antimicrobial activity against Staphylococcus aurious, Staphylococcus homonis, Salmonella typhi, and Shigella flexneria. The obtained result of antibacterial activity compared to standard drugs, and it was found that the synthesized compounds were almost same value of standard drug. Finally, it could be said from the in-vitro and in-silico study that the thiosemicarbazones derivatives are good antimicrobial agents.

Antiplasmodial activities of gold(I) complexes involving functionalized N-heterocyclic carbenes

A series of twenty five molecules, including imidazolium salts functionalized by N-, O- or S-containing groups and their corresponding cationic, neutral or anionic gold(I) complexes were evaluated on Plasmodium falciparum in vitro and then on Vero cells to determine their selectivity. Among them, eight new compounds were synthesized and fully characterized by spectroscopic methods. The X-ray structures of three gold(I) complexes are presented. Except one complex (18), all the cationic gold(I) complexes show potent antiplasmodial activity with IC50 in the micro- and submicromolar range, correlated with their lipophilicity. Structure-activity relationships enable to evidence a lead-complex (21) displaying a good activity (IC50=210nM) close to the value obtained with chloroquine (IC50=514nM) and a weak cytotoxicity.

Antimalarial activity of thiosemicarbazones and purine derived nitriles

Malaria is a devastating illness caused by multiple species of the Plasmodium genus. The parasite's falcipain proteases have been extensively studied as potential drug targets. Here we report the testing of two established cysteine protease inhibitor scaffolds against both chloroquine sensitive and chloroquine resistant parasites. A subset of purine derived nitriles killed the parasite with moderate potency, and these inhibitors do not seem to exert their antiproliferative effects as cysteine protease inhibitors. Compound potency was determined to be similar against both parasite strains, indicating a low probability of cross resistance with chloroquine. These compounds represent a novel antimalarial scaffold, and a potential starting point for the development new inhibitors.

Reversed-phase high-performance liquid chromatography of 4-(2-pyridyl)-1-piperazinethiocarboxylic acid 2-[1-(pyridyl)ethylidene]hydrazide dihydrochloride (NSC 348977), a synthetic thiosemicarbazone with antitumor activity

Reversed-phase HPLC conditions for the separation of 4-(2-pyridyl)-1-piperazinethiocarboxylic acid 2-[1-(pyridyl)-ethylidene]hydrazide dihydrochloride (NSC 348977, I), a synthetic thiosemicarbazone with antitumor activity, from mouse plasma have been investigated. Following denaturization and precipitation of the spiked plasma with acetonitrile, an aliquot of the supernatant was diluted with aqueous buffer and subjected to analysis on a Nova-Pak C18 column (150 x 3.9 mm I.D.) by isocratic elution with 50 mM aqueous potassium phosphate buffer (pH 6.8, containing 1 mM EDTA)-acetonitrile (60:40, v/v). The column effluent was monitored for UV absorption at 310 nm. Problems identified in the sample preparation and separation of I include sensitivity to oxygen, light, non-neutral pH and the presence of metal ions. These factors were seen to adversely influence sample recovery, and attempts were made to find conditions which minimize their effects.

Analogues of N-benzyloxydihydrotriazines: in vitro antimalarial activity against Plasmodium falciparum

The antimalarial activities of a series of chlorophenyloxyalkoxy and chlorophenalkoxy N-substituted diamino-dihydrotriazines were determined in vitro against three strains of Plasmodium falciparum (Malayan Camp, Vietnam Smith, FCB) with diverse levels of resistance to chloroquine, pyrimethamine, and cycloguanil. Parasite viability was assayed by the inhibition of the uptake of radiolabelled hypoxanthine. Most of the ID-50S of these compounds were less than 1.0 ng ml-1. Consistent differences in sensitivities to these compounds were observed and appeared to be strain related. The Malayan Camp was the most sensitive and Vietnam Smith was the least sensitive. These differences appeared to be related primarily to an inherent sensitivity of a particular strain to the series of analogues examined rather than to a pattern of cross-resistance to chloroquine, pyrimethamine, or cycloguanil.

In vitro susceptibility of Neisseria gonorrhoeae to 2-acetylpyridine thiosemicarbazones

MICs of 20 2-acetylpyridine thiosemicarbazones and penicillin were determined for 25 clinical isolates of beta-lactamase-positive and beta-lactamase-negative Neisseria gonorrhoeae strains. The compounds most active against the beta-lactamase-producing strains were the N4,N4-disubstituted derivatives and the thiosemicarbazone derivatives of the 2-acetylpyridines, followed by the other compounds related to the 2-acetylpyridine thiosemicarbazones.

2-Acetylpyridine thiosemicarbazones XI: 2-(alpha-Hydroxyacetyl)pyridine thiosemicarbazones as antimalarial and antibacterial agents

A series of 2-(alpha-hydroxyacetyl)pyridine thiosemicarbazones was synthesized as potential antimalarial and antibacterial agents. Their synthesis was achieved by the condensation of N4-mono- or N4,N4-disubstituted thiosemicarbazides with 2-(alpha-hydroxyacetyl)pyridine. The latter was prepared by selective bromine oxidation of (2-pyridinyl)-1,2-ethanediol. The new compounds show potent inhibitory activity against penicillin-sensitive as well as penicillin-resistant Neisseria gonorrhoeae (MIC, 0.5-0.004 micrograms/mL), against Neisseria meningitidis (MIC, 0.5-0.032 micrograms/mL), and Staphylococcus aureus (MIC, 0.5-2 micrograms/mL). Good in vitro antimalarial effects against Plasmodium falciparum (Smith strain; ID50, 6.7-38 ng/mL) were observed in most of these new agents, but only 3 of 12 compounds exhibit moderate in vivo activity against Plasmodium berghei. These new agents appear to be less toxic to the host and more water soluble than the corresponding 2-acetylpyridine thiosemicarbazones.

Plasmodium falciparum: mefloquine resistance produced in vitro

Camp and Smith strains of the human malaria parasite Plasmodium falciparum became resistant to mefloquine after continuous cultivation in the presence of the drug. The 50% inhibitory dose (ID(50)) values for mefloquine, as assessed by [(3)H]hypoxanthine incorporation, were found to have increased 4-fold, from 3 mug/l to 12 mug/l. The ID(50) values obtained by morphological examination of the cultures increased 10-fold. Resistance was stable in both strains either when grown in a drug-free medium or when kept frozen in liquid nitrogen. The mefloquine-resistant Camp strain remained sensitive to chloroquine and amodiaquine, and became slightly more resistant to quinine; there was increased sensitivity to pyrimethamine. The mefloquine-resistant Smith strain remained sensitive to amodiaquine and resistant to pyrimethamine; there was increased resistance to quinine, and an increase in sensitivity to chloroquine.

Effect of membrane filtration of antimalarial drug solutions on in vitro activity against Plasmodium falciparum

Antimalarial activities of chloroquine, mefloquine, amodiaquine, and quinine in vitro against Plasmodium falciparum were diminished as a consequence of membrane filtration. Filtered drug solutions gave ID(50) values up to 25-fold greater than those of non-filtered (ethanol-sterilized) drug solutions. Loss of activity by filtration was overcome by increasing the drug concentration prior to filtration. Water solutions filtered through Millex-GS filter units consistently showed an absorbance maximum at 277 nm, accompanied by a lesser peak at 225 nm. Water filtrates from Nucleopore and Millex-GV filters showed no absorbance at 277 nm and only slight absorbance was evident for the Gelman filter unit. Activity losses were attributed to extractable contaminating moieties in the membrane filters and/or drug binding to the membrane filters.