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.

Naphthyl bearing 1,3,4-thiadiazoleacetamides targeting the parasitic folate pathway as anti-infectious agents: in silico, synthesis, and biological approach.

Malaria is still a complex and lethal parasitic infectious disease, despite the availability of effective antimalarial drugs. Resistance of malaria parasites to current treatments necessitates new antimalarials targeting P. falciparum proteins. The present study reported the design and synthesis of a series of a 2-(4-substituted piperazin-1-yl)-N-(5-((naphthalen-2-yloxy)methyl)-1,3,4-thiadiazol-2-yl)acetamide hybrids for the inhibition of Plasmodium falciparum dihydrofolate reductase (PfDHFR) using computational biology tools followed by chemical synthesis, structural characterization, and functional analysis. The synthesized compounds were evaluated for their in vitro antimalarial activity against CQ-sensitive PfNF54 and CQ-resistant PfW2 strain. Compounds T5 and T6 are the most active compounds having anti-plasmodial activity against PfNF54 with IC50 values of 0.94 and 3.46 µM respectively. Compound T8 is the most active against the PfW2 strain having an IC50 of 3.91 µM. Further, these active hybrids (T5, T6, and T8) were also evaluated for enzyme inhibition assay against PfDHFR. All the tested compounds were non-toxic against the Hek293 cell line with good selectivity indices. Hemolysis assay also showed non-toxicity of these compounds on normal uninfected human RBCs. In silico molecular docking studies were carried out in the binding pocket of both the wild-type and quadruple mutant Pf-DHFR-TS to gain further insights into probable modes of action of active compounds. ADME prediction and physiochemical properties support their drug-likeness. Additionally, they were screened for antileishmanial activity against L. donovani promastigotes to explore broader applications. Thus, this study provides molecular frameworks for developing potent antimalarials and antileishmanial agents.

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 biological evaluation of morpholinopyrimidine derivatives as anti-inflammatory agents.

Here, we outline the synthesis of a few 2-methoxy-6-((4-(6-morpholinopyrimidin-4-yl)piperazin-1-yl)(phenyl)methyl)phenol derivatives and assess their anti-inflammatory activity in macrophage cells that have been stimulated by LPS. Among these newly synthesized morpholinopyrimidine derivatives, 2-methoxy-6-((4-methoxyphenyl)(4-(6-morpholinopyrimidin-4-yl)piperazin-1-yl)methyl)phenol (V4) and 2-((4-fluorophenyl)(4-(6-morpholinopyrimidin-4-yl)piperazin-1-yl)methyl)-6-methoxyphenol (V8) are two of the most active compounds which can inhibit the production of NO at non-cytotoxic concentrations. Our findings also showed that compounds V4 and V8 dramatically reduced iNOS and cyclooxygenase mRNA expression (COX-2) in LPS-stimulated RAW 264.7 macrophage cells; western blot analysis showed that the test compounds decreased the amount of iNOS and COX-2 protein expression, hence inhibiting the inflammatory response. We find through molecular docking studies that the chemicals had a strong affinity for the iNOS and COX-2 active sites and formed hydrophobic interactions with them. Therefore, use of these compounds could be suggested as a novel therapeutic strategy for inflammation-associated disorders.

Multicomponent Petasis reaction for the identification of pyrazine based multi-target directed anti-Alzheimer's agents: In-silico design, synthesis, and characterization.

Multi-target directed ligands (MTDLs) have recently attracted significant interest due to their exceptional effectiveness against multi-factorial Alzheimer's disease. The present work described the development of pyrazine-based MTDLs using multicomponent Petasis reaction for the dual inhibition of tau-aggregation and human acetylcholinesterase (hAChE). The molecular structure of synthesized ligands was validated by 1H & 13C NMR and mass spectrometry. The screened compounds were shown to have a strong inhibitory effect at 10 µM concentration against tau-oligomerization and hAChE, but only moderate inhibitory activity against Aß42. Among all the compounds, the half-maximal inhibitory concentration (IC50) for 21 and 24 against hAChE were 0.71 µM and 1.09 µM, respectively, while they displayed half-maximal effective concentrations (EC50) values of 2.21 µM and 2.71 µM for cellular tau-oligomerization, respectively. Additionally, an MTT experiment using tau-expressing SH-SY5Y neuroblastoma cells revealed that 21 was more neuroprotective than the FDA-approved medication donepezil. Furthermore, an MD simulation study was performed to investigate the dynamics and stability of AChE-21 and AChE-24 complexes in an aqueous environment. The MM-PBSA calculations were performed to evaluate the binding of 21 and 24 with AChE, and the relative binding energy was calculated as -870.578 and -875.697 kJ mol-1, respectively. As a result, the study offered insight into the design of new MTDLs and highlighted 21 as a potential roadblock to the development of anti-AD medications.

Identification of new oxospiro chromane quinoline-carboxylate antimalarials that arrest parasite growth at ring stage.

Malaria still threatens half the globe population despite successful Artemisinin-based combination therapy. One of the reasons for our inability to eradicate malaria is the emergence of resistance to current antimalarials. Thus, there is a need to develop new antimalarials targeting Plasmodium proteins. The present study reported the design and synthesis of 4, 6 and 7-substituted quinoline-3-carboxylates 9(a-o) and carboxylic acids 10(a-b) for the inhibition of Plasmodium N-Myristoyltransferases (NMTs) using computational biology tools followed by chemical synthesis and functional analysis. The designed compounds exhibited a glide score of -9.241 to -6.960 kcal/mol for PvNMT and -7.538 kcal/mol for PfNMT model proteins. Development of the synthesized compounds was established via NMR, HRMS and single crystal X-ray diffraction study. The synthesized compounds were evaluated for their in vitro antimalarial efficacy against CQ-sensitive Pf3D7 and CQ-resistant PfINDO lines followed by cell toxicity evaluation. In silico results highlighted the compound ethyl 6-methyl-4-(naphthalen-2-yloxy)quinoline-3-carboxylate (9a) as a promising inhibitor with a glide score of -9.084 kcal/mol for PvNMT and -6.975 kcal/mol for PfNMT with IC50 values of 6.58 µM for Pf3D7 line. Furthermore, compounds 9n and 9o exhibited excellent anti-plasmodial activity (Pf3D7 IC50 = 3.96, 6.71 µM, and PfINDO IC50 = 6.38, 2.8 µM, respectively). The conformational stability of 9a with the active site of the target protein was analyzed through MD simulation and was found concordance with in vitro results. Thus, our study provides scaffolds for the development of potent antimalarials targeting both Plasmodium vivax and Plasmodium falciparum.Communicated by Ramaswamy H. Sarma.

Recent advancements in chromone as a privileged scaffold towards the development of small molecules for neurodegenerative therapeutics.

Neurodegenerative disorders, i.e., Alzheimer's or Parkinson's disease, involve progressive degeneration of the central nervous system, resulting in memory loss and cognitive impairment. The intensification of neurodegenerative research in recent years put some molecules into clinical trials, but still there is an urgent need to develop effective therapeutic molecules to combat these diseases. Chromone is a well-identified privileged structure for the design of well-diversified therapeutic molecules of potential pharmacological interest, particularly in the field of neurodegeneration. In this short review, we focused on the recent advancements and developments of chromones for neurodegenerative therapeutics. Different small molecules were reviewed as multi-target-directed ligands (MTDLs) with potential inhibition of AChE, BuChE, MAO-A, MAO-B, Aß plaque formation and aggregation. Recently developed MTDLs emphasized that the chromone scaffold has the potential to develop new molecules for the treatment of neurodegenerative diseases.

An insight into the recent development of the clinical candidates for the treatment of malaria and their target proteins.

Malaria is an endemic disease, prevalent in tropical and subtropical regions which cost half of million deaths annually. The eradication of malaria is one of the global health priority nevertheless, current therapeutic efforts seem to be insufficient due to the emergence of drug resistance towards most of the available drugs, even first-line treatment ACT, unavailability of the vaccine, and lack of drugs with a new mechanism of action. Intensification of antimalarial research in recent years has resulted into the development of single dose multistage therapeutic agents which has advantage of overcoming the antimalarial drug resistance. The present review explored the current progress in the development of new promising antimalarials against prominent target proteins that have the potential to be a clinical candidate. Here, we also reviewed different aspects of drug resistance and highlighted new drug candidates that are currently in a clinical trial or clinical development, along with a few other molecules with excellent antimalarial activity overs ACTs. The summarized scientific value of previous approaches and structural features of antimalarials related to the activity are highlighted that will be helpful for the development of next-generation antimalarials.