Design, synthesis, and characterization of novel aminoalcohol quinolines with strong in vitro antimalarial activity

Molecular dynamics and NMR reveal the coexistence of H-bond-assisted and through-space JFH coupling in fluorinated amino alcohols

The JFH coupling constants in fluorinated amino alcohols were investigated through experimental and theoretical approaches. The experimental JFH couplings were only reproduced theoretically when explicit solvation through molecular dynamics (MD) simulations was conducted in DMSO as the solvent. The combination of MD conformation sampling and DFT NMR spin-spin coupling calculations for these compounds reveals the simultaneous presence of through-space (TS) and hydrogen bond (H-bond) assisted JFH coupling between fluorine and hydrogen of the NH group. Furthermore, MD simulations indicate that the hydrogen in the amino group participates in both an intermolecular bifurcated H-bond with DMSO and in transmitting the observed JFH coupling. The contribution of TS to the JFH coupling is due to the spatial proximity of the fluorine and the NH group, aided by a combination of the non-bonding transmission pathway and the hydrogen bonding pathway. The experimental JFH coupling observed for the molecules studied should be represented as 4TS/1hJFH coupling.

Reinvestigation of diphenylmethylpiperazine analogues of pyrazine as new class of Plasmodial cysteine protease inhibitors for the treatment of malaria

Malaria eradication is still a global challenge due to the lack of a broadly effective vaccine and the emergence of drug resistance to most of the currently available drugs as part of the mainline artemisinin-based combination therapy. A variety of experimental approaches are quite successful in identifying and synthesizing new promising pharmacophore hybrids with distinct mechanisms of action. Based on our recent findings, the current study demonstrates the reinvestigation of a series of diphenylmethylpiperazine and pyrazine-derived molecular hybrids. Pyrazine-derived molecular hybrids were screened to investigate the antiplasmodial activity on drug-susceptible Pf3D7 and drug-resistant PfW2 strains. The selected compounds were shown to be potent dual inhibitors of cysteine protease PfFP2 and PfFP3. Time-course parasitic development study demonstrated that compounds were able to arrest the growth of the parasite at the early trophozoite stage. The compounds did not show hemolysis of red blood cells and showed selectivity to the parasite compared with the mammalian Vero and A5489 cell lines. The study underlined HR5 and HR15 as a new class of Plasmodial falcipain inhibitors with an IC50 of 6.2 μM and 5.9 μM for PfFP2 and 6.8 μM and 6.4 μM for PfFP3, respectively. Both compounds have antimalarial efficacy with IC50 values of 3.05 μM and 2.80 μM for the Pf3D7 strain, and 4.35 μM and 3.39 μM for the PfW2 strain, respectively. Further structural optimization may turn them into potential Plasmodial falcipain inhibitors for malaria therapeutics.

Development of diphenylmethylpiperazine hybrids of chloroquinoline and triazolopyrimidine using Petasis reaction as new cysteine proteases inhibitors for malaria therapeutics

Malaria is a widespread infectious disease, causing nearly 247 million cases in 2021. The absence of a broadly effective vaccine and rapidly decreasing effectiveness of most of the currently used antimalarials are the major challenges to malaria eradication efforts. To design and develop novel antimalarials, we synthesized a series of 4,7-dichloroquinoline and methyltriazolopyrimidine analogues using a multi-component Petasis reaction. The synthesized molecules (11-31) were screened for in-vitro antimalarial activity against drug-sensitive and drug-resistant strains of Plasmodium falciparum with an IC₅₀ value of 0.53 μM. The selected compounds were screened to evaluate in-vitro and in-silico enzyme inhibition efficacy against two cysteine proteases, PfFP2 and PfFP3. The compounds 15 and 17 inhibited PfFP2 with an IC₅₀ = 3.5 and 4.8 μM, respectively and PfFP3 with an IC₅₀ = 4.9 and 4.7 μM, respectively. Compounds 15 and 17 were found equipotent against the Pf3D7 strain with an IC₅₀ value of 0.74 μM, whereas both were displayed IC₅₀ values of 1.05 μM and 1.24 μM for the PfW2 strain, respectively. Investigation of effect of compounds on parasite development demonstrated that compounds were able to arrest the growth of the parasites at trophozoite stage. The selected compounds were screened for in-vitro cytotoxicity against mammalian lines and human red-blood-cell (RBC), which demonstrated no significant cytotoxicity associated with the molecules. In addition, in silico ADME prediction and physiochemical properties supported the drug-likeness of the synthesized molecules. Thus, the results highlighted the diphenylmethylpiperazine group cast on 4,7-dichloroquinoline and methyltriazolopyrimidine using Petasis reaction may serve as models for the development of new antimalarial agents.

Design, Synthesis, and Antiprotozoal Evaluation of New Promising 2,9-Bis[(substituted-aminomethyl)]-4,7-phenyl-1,10-phenanthroline Derivatives, a Potential Alternative Scaffold to Drug Efflux

A series of novel 2,9-bis[(substituted-aminomethyl)]-4,7-phenyl-1,10-phenanthroline derivatives was designed, synthesized, and evaluated in vitro against three protozoan parasites (Plasmodium falciparum, Leishmania donovani and Trypanosoma brucei brucei). Pharmacological results showed antiprotozoal activity with IC50 values in the sub and μM range. In addition, the in vitro cytotoxicity of these original molecules was assessed with human HepG2 cells. The substituted diphenylphenanthroline 1l was identified as the most potent antimalarial derivative with a ratio of cytotoxic to antiparasitic activities of 505.7 against the P. falciparum CQ-resistant strain W2. Against the promastigote forms of L. donovani, the phenanthrolines 1h, 1j, 1n and 1o were the most active with IC50 from 2.52 to 4.50 μM. The phenanthroline derivative 1o was also identified as the most potent trypanosomal candidate with a selectivity index (SI) of 91 on T. brucei brucei strain. FRET melting and native mass spectrometry experiments evidenced that the nitrogen heterocyclic derivatives bind the telomeric G-quadruplexes of P. falciparum and Trypanosoma. Moreover, as the telomeres of the parasites P. falciparum and Trypanosoma could be considered to be possible targets of this kind of nitrogen heterocyclic derivatives, their potential ability to stabilize the parasitic telomeric G-quadruplexes have been determined through the FRET melting assay and by native mass spectrometry.

Divergent Synthesis, Antiproliferative and Antimicrobial Studies of 1,3-Aminoalcohol and 3-Amino-1,2-Diol Based Diaminopyrimidines

A series of novel diaminopyrimidines containing pinane moieties were synthesized via an efficient methodology starting from pinane-based aminoalcohols, aminodiols and 2,4-dichloropyrimidines. Bioassay tests demonstrated that compound 18a displayed much stronger antiproliferative activities against four human cancer cell lines (HeLa, Siha, MDA-MB-231, MCF-7 and A2780) than positive control cisplatin. In particular, compound 22a was found to be selective in inhibiting HeLa cell proliferation with cancer cell growth inhibition values higher than 95 %. Moreover, the in vitro screening of prepared compounds against different bacterial and fungal strains is reported. The results revealed that 12b and 17a, the most promising compounds, displayed selective inhibition for the Gram-positive bacteria (B. subtilis and S. aureus) with percent inhibition values ranging from 75 to 95 % at 10 μg/mL concentration. Both selective inhibition and the in vitro activity values demonstrated that these compounds have the potential to be developed into clinically important therapeutic choices for the treatment of infections caused by B. subtilis and S. aureus.

The State of Art of Extracellular Traps in Protozoan Infections (Review)

Protozoan parasite infection causes severe diseases in humans and animals, leading to tremendous economic and medical pressure. Natural immunity is the first line of defence against parasitic infection. Currently, the role of natural host immunity in combatting parasitic infection is unclear, so further research on natural host immunity against parasites will provide a theoretical basis for the prevention and treatment of related parasitic diseases. Extracellular traps (ETs) are an important natural mechanism of immunity involving resistance to pathogens. When immune cells such as neutrophils and macrophages are stimulated by external pathogens, they release a fibrous network structure, consisting mainly of DNA and protein, that can capture and kill a variety of extracellular pathogenic microorganisms. In this review, we discuss the relevant recently reported data on ET formation induced by protozoan parasite infection, including the molecular mechanisms involved, and discuss the role of ETs in the occurrence and development of parasitic diseases.

Catalyst-free aerobic radical cascade reactions of o-vinylphenylisocyanides with thiols to access 2-thio-substituted quinolines

We herein report an efficient and green aerobic radical cascade reaction of o-vinylphenylisocyanides with thiols to access a broad range of 2-thio-substituted quinolines without the need for additional catalysts or oxidants.