4-Aminoquinoline derived antimalarials: synthesis, antiplasmodial activity and heme polymerization inhibition studies

Synthesis, Biological Evaluation, and Molecular Modeling Studies of Chiral Chloroquine Analogues as Antimalarial Agents

In a focused exploration, we designed, synthesized, and biologically evaluated chiral conjugated new chloroquine (CQ) analogues with substituted piperazines as antimalarial agents. In vitro as well as in vivo studies revealed that compound 7c showed potent activity (in vitro 50% inhibitory concentration, 56.98 nM for strain 3D7 and 97.76 nM for strain K1; selectivity index in vivo [up to at a dose of 12.5 mg/kg of body weight], 3,510) as a new lead antimalarial agent. Other compounds (compounds 6b, 6d, 7d, 7h, 8c, 8d, 9a, and 9c) also showed moderate activity against a CQ-sensitive strain (3D7) and superior activity against a CQ-resistant strain (K1) of Plasmodium falciparum Furthermore, we carried out docking and three-dimensional quantitative structure-activity relationship (3D-QSAR) studies of all in-house data sets (168 molecules) of chiral CQ analogues to explain the structure-activity relationships (SAR). Our new findings specify the significance of the H-bond interaction with the side chain of heme for biological activity. In addition, the 3D-QSAR study against the 3D7 strain indicated the favorable and unfavorable sites of CQ analogues for incorporating steric, hydrophobic, and electropositive groups to improve the antimalarial activity.

Synthesis and Evaluation of Chirally Defined Side Chain Variants of 7-Chloro-4-Aminoquinoline To Overcome Drug Resistance in Malaria Chemotherapy

A novel 4-aminoquinoline derivative [(S)-7-chloro-N-(4-methyl-1-(4-methylpiperazin-1-yl)pentan-2-yl)-quinolin-4-amine triphosphate] exhibiting curative activity against chloroquine-resistant malaria parasites has been identified for preclinical development as a blood schizonticidal agent. The lead molecule selected after detailed structure-activity relationship (SAR) studies has good solid-state properties and promising activity against in vitro and in vivo experimental malaria models. The in vitro absorption, distribution, metabolism, and excretion (ADME) parameters indicate a favorable drug-like profile.

Antimalarial activity of novel 4-aminoquinolines active against drug resistant strains

In the present study we have synthesized a new class of 4-aminoquinolines and evaluated against Plasmodium falciparum in vitro (3D7-sensitive strain & K1-resistant strain) and Plasmodium yoelii in vivo (N-67 strain). Among the series, eleven compounds (5, 6, 7, 8, 9, 11, 12, 13, 14, 15 and 21) showed superior antimalarial activity against K1 strain as compared to CQ. In addition, all these analogues showed 100% suppression of parasitemia on day 4 in the in vivo mouse model against N-67 strain when administered orally. Further, biophysical studies suggest that this series of compounds act on heme polymerization target.

Synthesis and antimalarial activity of new 4-aminoquinolines active against drug resistant strains

In the present study we have synthesized a new class of 4-aminoquinoline derivatives and bioevaluated them for antimalarial activity against theP. falciparum in vitro(3D7 & K1) andP. yoelii in vivo(N-67 strain).

Chloroquine-containing compounds: a patent review (2010 - 2014)

INTRODUCTION

Chloroquine (CQ) has been well known for its antimalarial effects since World War II. However, it is gradually being phased out from clinical use against malaria due to emergence of CQ-resistant Plasmodium falciparum strains. Besides low cost and tolerability, ongoing research has revealed interesting biochemical properties of CQ that have inspired its repurposing/repositioning in the management of various infectious/noninfectious diseases. Consequently, several novel compounds and compositions based on its scaffold have been studied and patented.

AREAS COVERED

In this review, patents describing CQ and its derivatives/compositions over the last 5 years are analyzed. The review highlights the rationale, chemical structures, biological evaluation and potential therapeutic application of CQ, its derivatives and compositions.

EXPERT OPINION

Repurposing efforts have dominantly focused on racemic CQ with no studies exploring the effect of the (R) and (S) enantiomers, which might potentially have additional benefits in other diseases. Additionally, evaluating other similarly acting antimalarials in clinical use and structural analogs could help maximize the intrinsic value of the 4-aminoquinolines. With regard to cancer therapy, successful repurposing of CQ-containing compounds will require linking the mode of action of these antimalarials with the signaling pathways that drive cancer cell proliferation to facilitate the development of a 4-amino-7-chloroquinoline that can be used as a synergistic partner in anticancer combination chemotherapy.

Synthesis of chiral chloroquine and its analogues as antimalarial agents

In this investigation, we describe a new approach to chiral synthesis of chloroquine and its analogues. All tested compounds displayed potent activity against chloroquine sensitive as well as chloroquine resistant strains of Plasmodium falciparum in vitro and Plasmodium yoelii in vivo. Compounds S-13 b, S-13c, S-13 d and S-13 i displayed excellent in vitro antimalarial activity with an IC50 value of 56.82, 60.41, 21.82 and 7.94 nM, respectively, in the case of resistant strain. Furthermore, compounds S-13a, S-13c and S-13 d showed in vivo suppression of 100% parasitaemia on day 4 in the mouse model against Plasmodium yoelii when administered orally. These results underscore the application of synthetic methodology and need for further lead optimization.

Antiplasmodial activity of new 4-aminoquinoline derivatives against chloroquine resistant strain

Emergence and spread of multidrug resistant strains of Plasmodium falciparum has severely limited the antimalarial chemotherapeutic options. In order to overcome the obstacle, a set of new side-chain modified 4-aminoquinolines were synthesized and screened against chloroquine-sensitive (3D7) and chloroquine-resistant (K1) strains of P. falciparum. The key feature of the designed molecules is the use of methylpiperazine linked α, β(3)- and γ-amino acids to generate novel side chain modified 4-aminoquinoline analogues. Among the evaluated compounds, 20c and 30 were found more potent than CQ against K1 and displayed a four-fold and a three-fold higher activity respectively, with a good selectivity index (SI=5846 and 11,350). All synthesized compounds had resistance index between 1.06 and >14.13 as against 47.2 for chloroquine. Biophysical studies suggested that this series of compounds act on heme polymerization target.

1-{[(Z)-Cyclo-pentyl-idene]amino}-3-phenyl-thio-urea

The sample of the title compound, C₁₂H₁₅N₃S, chosen for study consisted of triclinic crystals twinned by a 180° rotation about the a axis. The five-membered ring adopts a twisted conformation. The dihedral angle between the phenyl ring and the mean plane of the thio­urea unit is 78.22 (8)°. In the crystal, molecules are linked via pairs of N—H⋯S hydrogen bonds forming inversion dimers.

An Efficient One-Pot Synthesis of bis-1-(aroyl)-3-(aryl)thiourea

A three-component and one-pot reaction between 2,6-diaminopyridine or 1,2-diaminobenzene and ammonium thiocyanate with the subsequent addition of an aroyl chloride afforded the bis-1-(aroyl)-3-(aryl)thiourea in excellent yields. It was important to make the thiocyanate derivatives first and then to use those to prepare the thiourea derivatives.

Design, synthesis of 4-aminoquinoline-derived thiazolidines and their antimalarial activity and heme polymerization inhibition studies

The present study describes the synthesis of a series of new 4-aminoquinoline-derived thiazolidines and evaluation of their antimalarial activity against a NF-54 strain of Plasmodium falciparum in vitro and N-67 strain of Plasmodium yoelii in vivo. Among the series, two compounds, 2-(4-chloro-phenyl)-thiazolidine-4-carboxylic acid [2-(7-chloro-quinolin-4-ylamino)-ethyl]-amide hydrochloride (14) and 2-(2,6-dichloro-phenyl)-thiazolidine-4-carboxylic acid [2-(7-chloro-quinolin-4-ylamino)-ethyl]-amide hydrochloride (22) exhibited significant suppression of parasitaemia in the in vivo assay. All the analogues were found to form strong complex with haematin and inhibited the β-haematin formation in vitro. These results suggest that these compounds act on heme polymerization target.

Synthesis of uriedo and thiouriedo derivatives of peptide conjugated heterocycles - A new class of promising antimicrobials

Forty five new derivatives of ureas and thioureas were synthesized by the reaction of peptide conjugated heterocycles with isocyanates and isothiocyanates respectively. All the compounds have been characterized by IR, (1)H NMR, mass and elemental analysis. The compounds were evaluated for their ability to inhibit the growth of a panel of microorganisms and all the synthesized compounds displayed an excellent antimicrobial activity. From structure-activity relationship studies, it was apparent that thioureas infact is slightly more active than ureas. Also, substituents on the phenyl ring of the title compounds play a key role in the activity. Further, compound 40 is nearly twenty times more potent than the standard used. These results present a platform for the further studies in this line.