Lerisetron Analogues with Antimalarial Properties: Synthesis, Structure-Activity Relationship Studies, and Biological Assessment

Design, Synthesis and Evaluation of Praziquantel Analogues and New Molecular Hybrids as Potential Antimalarial and Anti-Schistosomal Agents

Malaria and schistosomiasis are two of the neglected tropical diseases that persistently wreak havoc worldwide. Although many antimalarial drugs such as chloroquine are readily available, the emergence of drug resistance necessitates the development of new therapies to combat this disease. Conversely, Praziquantel (PZQ) remains the sole effective drug against schistosomiasis, but its extensive use raises concerns about the potential for drug resistance to develop. In this project, the concept of molecular hybridization was used as a strategy to design the synthesis of new molecular hybrids with potential antimalarial and antischistosomal activity. A total of seventeen molecular hybrids and two PZQ analogues were prepared by coupling 6-alkylpraziquanamines with cinnamic acids and cyclohexane carboxylic acid, respectively. The synthesised compounds were evaluated for their antimalarial and antischistosomal activity; while all of the above compounds were inactive against Plasmodium falciparum (IC₅₀ > 6 µM), many were active against schistosomiasis with four particular compounds exhibiting up to 100% activity against newly transformed schistosomula and adult worms at 50 µM. Compared to PZQ, the reference drug, the activity of which is 91.7% at 1 µM, one particular molecular hybrid, compound 32, which bears a para-isopropyl group on the cinnamic acid moiety, exhibited a notable activity at 10 µM (78.2% activity). This compound has emerged as the front runner candidate that might, after further optimization, hold promise as a potential lead compound in the fight against schistosomiasis.

Antiplasmodial activity, structure-activity relationship and studies on the action of novel benzimidazole derivatives

Malaria cases and deaths keep being excessively high every year. Some inroads gained in the last two decades have been eroded especially due to the surge of resistance to most antimalarials. The search for new molecules that can replace the ones currently in use cannot stop. In this report, the synthesis of benzimidazole derivatives guided by structure-activity parameters is presented. Thirty-six molecules obtained are analyzed according to their activity against P. falciparum HB3 strain based on the type of substituent on rings A and B, their electron donor/withdrawing, as well as their dimension/spatial properties. There is a preference for electron donating groups on ring A, such as Me in position 5, or better, 5, 6-diMe. Ring B must be of the pyridine type such as picolinamide, other modifications are generally not favorable. Two molecules, 1 and 33 displayed antiplasmodial activity in the high nanomolar range against the chloroquine sensitive strain, with selectivity indexes above 10. Activity results of 1, 12 and 16 on a chloroquine resistance strain indicated an activity close to chloroquine for compound 1. Analysis of some of their effect on the parasites seem to suggest that 1 and 33 affect only the parasite and use a route other than interference with hemozoin biocrystallization, the route used by chloroquine and most antimalarials.

A Comprehensive Account on Recent Progress in Pharmacological Activities of Benzimidazole Derivatives

Nowadays, nitrogenous heterocyclic molecules have attracted a great deal of interest among medicinal chemists. Among these potential heterocyclic drugs, benzimidazole scaffolds are considerably prevalent. Due to their isostructural pharmacophore of naturally occurring active biomolecules, benzimidazole derivatives have significant importance as chemotherapeutic agents in diverse clinical conditions. Researchers have synthesized plenty of benzimidazole derivatives in the last decades, amidst a large share of these compounds exerted excellent bioactivity against many ailments with outstanding bioavailability, safety, and stability profiles. In this comprehensive review, we have summarized the bioactivity of the benzimidazole derivatives reported in recent literature (2012-2021) with their available structure-activity relationship. Compounds bearing benzimidazole nucleus possess broad-spectrum pharmacological properties ranging from common antibacterial effects to the world's most virulent diseases. Several promising therapeutic candidates are undergoing human trials, and some of these are going to be approved for clinical use. However, notable challenges, such as drug resistance, costly and tedious synthetic methods, little structural information of receptors, lack of advanced software, and so on, are still viable to be overcome for further research.

Synthesis and Evaluation of Chalcone-Quinoline Based Molecular Hybrids as Potential Anti-Malarial Agents

Molecular hybridization is a drug discovery strategy that involves the rational design of new chemical entities by the fusion (usually via a covalent linker) of two or more drugs, both active compounds and/or pharmacophoric units recognized and derived from known bioactive molecules. The expected outcome of this chemical modification is to produce a new hybrid compound with improved affinity and efficacy compared to the parent drugs. Additionally, this strategy can result in compounds presenting modified selectivity profiles, different and/or dual modes of action, reduced undesired side effects and ultimately lead to new therapies. In this study, molecular hybridization was used to generate new molecular hybrids which were tested against the chloroquine sensitive (NF54) strain of P. falciparum. To prepare the new molecular hybrids, the quinoline nucleus, one of the privileged scaffolds, was coupled with various chalcone derivatives via an appropriate linker to produce a total of twenty-two molecular hybrids in 11%–96% yield. The synthesized compounds displayed good antiplasmodial activity with IC₅₀ values ranging at 0.10–4.45 μM.

Discovery and development of 2-aminobenzimidazoles as potent antimalarials

The emergence of Plasmodium falciparum resistance to frontline antimalarials, including artemisinin combination therapies, highlights the need for new molecules that act via novel mechanisms of action. Herein, we report the design, synthesis and antimalarial activity of a series of 2-aminobenzimidazoles, featuring a phenol moiety that is crucial to the pharmacophore. Two potent molecules exhibited IC₅₀ values against P. falciparum 3D7 strain of 42 ± 4 (3c) and 43 ± 2 nM (3g), and high potency against strains resistant to chloroquine (Dd2), artemisinin (Cam3.II^C580Y) and PfATP4 inhibitors (SJ557733), while demonstrating no cytotoxicity against human cells (HEK293, IC₅₀ > 50 μM). The most potent molecule, possessing a 4,5-dimethyl substituted phenol (3r) displayed an IC₅₀ value of 6.4 ± 0.5 nM against P. falciparum 3D7, representing a 12-fold increase in activity from the parent molecule. The 2-aminobenzimidazoles containing a N¹-substituted phenol represent a new class of molecules that have high potency in vitro against P. falciparum malaria and low cytotoxicity. They possessed attractive pharmaceutical properties, including low molecular weight, high ligand efficiency, high solubility, synthetic tractability and low in vitro clearance in human liver microsomes.

BENZIMIDAZOLE AS A PROMISING ANTIVIRAL HETEROCYCLIC SCAFFOLD: A REVIEW

Heterocyclic derivatives are unavoidable in many fields of natural disciplines. These derivatives play numerous significant roles in research, medication, and nature. Nitrogenous heterocyclic derivatives extremely are the main target of concern in synthetic chemistry to ensue active natural products with pharmaceuticals and agrochemicals interest. Benzimidazole skeleton is another example of some active heterocyclic moiety that significantly contributes in the numerous bioactive of essential compounds. Benzimidazole skeleton is studied as a prominent moiety of biologically active compounds with various activities including antimicrobial, antiprotozoal, anticancer, antiviral, acetylcholinesterase, antihistaminic, anti-inflammatory, antimalarial, analgesic, anti-HIV and antitubercular. Therefore, in this review we summarize the various antiviral activities of several benzimidazole derivatives and outline the correlation among the structures of different benzimidazoles scaffold with their therapeutic significance.