Platinum(ii)-chloroquine complexes are antimalarial agents against blood and liver stages by impairing mitochondrial function

Exploring antimalarial potential: Conjugating organometallic moieties with organic fragments for enhanced efficacy

In the search for novel ligands with efficacy against various diseases, particularly parasitic diseases, molecular hybridization of organometallic units into biologically active scaffolds has been hailed as an appealing strategy in medicinal chemistry. The conjugation to organometallic fragments can be achieved by an appropriate linker or by directly coordinating the existing drugs to a metal. The success of Ferroquine (FQ, SR97193), an effective chloroquine-ferrocene conjugate currently undergoing the patient-exploratory phase as a combination therapy with the novel triaminopyrimidine ZY-19489 for malaria, has sparked intense interest in organometallic compound drug discovery. We present the evolution of organometallic antimalarial agents over the last decade, focusing on the parent moiety's class and the type of organometallics involved. Four main organometallic antimalarial compounds have been chosen based on conjugated organic moieties: existing antimalarial drugs, other clinical drugs, hybrid drugs, and promising scaffolds of thiosemicarbazones, benzimidazoles, and chalcones, in particular. The presented insights contribute to the ongoing discourse on organometallic compound drug development for malaria diseases.

N-(coumarin-3-yl)cinnamamide Promotes Immunomodulatory, Neuroprotective, and Lung Function-Preserving Effects during Severe Malaria

Plasmodium berghei ANKA (PbA) infection in mice resembles several aspects of severe malaria in humans, such as cerebral malaria and acute respiratory distress syndrome. Herein, the effects of N-(coumarin-3-yl)cinnamamide (M220) against severe experimental malaria have been investigated. Treatment with M220 proved to protect cognitive abilities and lung function in PbA-infected mice, observed by an object recognition test and spirometry, respectively. In addition, treated mice demonstrated decreased levels of brain and lung inflammation. The production and accumulation of microglia, and immune cells that produce the inflammatory cytokines TNF and IFN-γ, decreased, while the production of the anti-inflammatory cytokine IL-10 by innate and adaptive immune cells was enhanced. Treatment with M220 promotes immunomodulatory, neuroprotective, and lung function-preserving effects during experimental severe malaria. Therefore, it may be an interesting therapeutic candidate to treat severe malaria effects.

Transition Metal Complexes as Antimalarial Agents: A Review

In antimalarial drug development research, overcoming drug resistance has been a major challenge for researchers. Nowadays, several drugs like chloroquine, mefloquine, sulfadoxine, and artemisinin are used to treat malaria. But increment in drug resistance has pushed researchers to find novel drugs to tackle drug resistance problems. The idea of using transition metal complexes with pharmacophores as ligands/ligand pendants to show enhanced antimalarial activity with a novel mechanism of action has gained significant attention recently. The advantages of metal complexes include tunable chemical/physical properties, redox activity, avoiding resistance factors, etc. Several recent reports have successfully demonstrated that the metal complexation of known organic antimalarial drugs can overcome drug resistance by showing enhanced activities than the parent drugs. This review has discussed the fruitful research works done in the past few years falling into this criterion. Based on transition metal series (3d, 4d, or 5d), the antimalarial metal complexes have been divided into three broad categories (3d, 4d, or 5d metal-based), and their activities have been compared with the similar control complexes as well as the parent drugs. Furthermore, we have also commented on the potential issues and their possible solution for translating these metal-based antimalarial complexes into the clinic.

Antimalarial Agents Derived from Metal-Amodiaquine Complexes with Activity in Multiple Stages of the Plasmodium Life Cycle

Malaria is the one of the deadliest infectious diseases worldwide. Chemically, quinolines are excellent ligands for metal coordination and are deployed as drugs for malaria treatment. There is a growing body of evidence indicating that metal complexes can be conjugated with antimalarial quinolines to be used as chemical tools to overcome the disadvantages of quinolines, improving their bioactive speciation, cellular distribution, and subsequently broadening the spectrum of activity to multiple stages of the complex Plasmodium life cycle. In this study, four novel complexes of ruthenium(II)- and gold(I)-containing amodiaquine (AQ) were synthesized, and a careful chemical characterization revealed the precise coordination site of AQ to the metals. Their speciation in solution was investigated, demonstrating the stability of the quinoline-metal bond. RuII - and AuI -AQ complexes were demonstrated to be potent and efficacious in inhibiting parasite growth in multiple stages of the Plasmodium life cycle as assayed in vitro and in vivo. These properties could be attributed to the ability of the metal-AQ complexes to reproduce the suppression of heme detoxification induced by AQ, while also inhibiting other processes in the parasite life cycle; this can be attributed to the action of the metallic species. Altogether, these findings indicate that metal coordination with antimalarial quinolines is a potential chemical tool for drug design and discovery in malaria and other infectious diseases susceptible to quinoline treatment.

Inhibition of mycobacteria proliferation in macrophages by low cisplatin concentration through phosphorylated p53-related apoptosis pathway

BACKGROUND

Drug resistance is a prominent problem in the treatment of tuberculosis, so it is urgent to develop new anti- tuberculosis drugs. Here, we investigated the effects and mechanisms of cisplatin (DDP) on intracellular Mycobacterium smegmatis to tap the therapeutic potential of DDP in mycobacterial infection.

RESULTS

Macrophages infected with Mycobacterium smegmatis were treated with DDP alone or combined with isoniazid or rifampicin. The results showed that the bacterial count in macrophages decreased significantly after DDP (≤ 6 μg/mL) treatment. When isoniazid or rifampicin was combined with DDP, the number of intracellular mycobacteria was also significantly lower than that of isoniazid or rifampicin alone. Apoptosis of infected cells increased after 24 h of DDP treatment, as shown by flow cytometry and transmission electron microscopy detection. Transcriptome sequencing showed that there were 1161 upregulated and 645 downregulated differentially expressed genes (DEGs) between the control group and DDP treatment group. A Trp53-centered protein interaction network was found based on the top 100 significant DEGs through STRING and Cytoscape software. The expression of phosphorylated p53, Bax, JAK, p38 MAPK and PI3K increased after DDP treatment, as shown by Western blot analysis. Inhibitors of JAK, PI3K or p38 MAPK inhibited the increase in cell apoptosis and the reduction in the intracellular bacterial count induced by DDP. The p53 promoter Kevetrin hydrochloride scavenges intracellular mycobacteria. If combined with DDP, Kevetrin hydrochloride could increase the effect of DDP on the elimination of intracellular mycobacteria. In conclusion, DDP at low concentrations could activate the JAK, p38 MAPK and PI3K pathways in infected macrophages, promote the phosphorylation of p53 protein, and increase the ratio of Bax to Bcl-2, leading to cell apoptosis, thus eliminating intracellular bacteria and reducing the spread of mycobacteria.

CONCLUSION

DDP may be a new host-directed therapy for tuberculosis treatment, as well as the p53 promoter Kevetrin hydrochloride.

Development of Mitochondria Targeting AIE-Active Cyclometalated Iridium Complexes as Potent Antimalarial Agents

The emergence of resistance to conventional antimalarial treatments remains a major cause for concern. New drugs that target the distinct development stages of Plasmodium parasites are required to address this risk. Herein, water-soluble aggregation-induced emission active cyclometalated iridium(III) polypyridyl complexes (Ir1-Ir12) are developed for the elimination of malaria parasites. Remarkably, these complexes show potent antimalarial activity in low nanomolar range against 3D7 (chloroquine and artemisinin sensitive strain), RKL9 (chloroquine resistant strain), and R539T (artemisinin resistant strains) strains of Plasmodium falciparum with faster killing rate of malaria parasites. Concomitantly, these complexes exhibit efficient in vivo antimalarial activity against both the asexual and gametocyte stages of Plasmodium berghei malaria parasite, suggesting promising transmission-blocking potential. The complexes tend to localize into mitochondria of P. falciparum determined by image and cell-based assay. The mechanistic studies reveal that these complexes exert their antimalarial activity by increasing reactive oxygen species levels and disrupting its mitochondrial membrane potential. Furthermore, the mitochondrial-dependent antimalarial activity of these complexes is confirmed in yeast model. Thus, this study for the first time highlights the potential role of targeting P. falciparum mitochondria by iridium complexes in discovering and developing the next-generation antimalarial agents for treating multidrug resistant malaria parasites.

Copper (I)-Chloroquine Complexes: Interactions with DNA and Ferriprotoporphyrin, Inhibition of β-Hematin Formation and Relation to Antimalarial Activity

A new Cu(I)-chloroquine (CQ) complex [Cu(CQ)(PPh₃)₂]NO₃ (1) was synthesized and characterized, and its mechanism of action studied concomitant with the previously reported complex [Cu(CQ)₂]Cl (2). These copper (I) coordination compounds can be considered as potential antimalarial agents because they show better inhibition of the CQ-resistant strain in in vitro studies than CQ alone. In comparison with other metal-CQ complexes, only the gold complex was similar to (1), i.e., more active than CQ against both CQ-susceptible (3D7) and CQ-resistant strains (W2). These two copper (I)-compounds also demonstrated higher antiplasmodial activity against W2 than other copper complexes reported to date. This suggests that the incorporation of the copper metal center enhanced the biological activity of CQ. To better understand their significant growth inhibition of the Plasmodium falciparum parasite, the interaction with two essential molecular targets for the survival and proliferation of the malarial parasite were studied. These were the ferriprotoporphyrin group and the DNA, both important targets for current antimalarial drugs at the asexual erythrocytic stages. Both compounds (1,2) exhibited significant interactions with these targets. In particular, interactions with the DNA were dominated by the intercalator properties of the CQ ligand but may have also been affected by the presence of copper. Overall, these compounds were better parasitic inhibitors than chloroquine diphosphate (CQDP) alone or other previously reported metal-CQ complexes such as platinum, ruthenium and gold.

Title: A Comprehensive Review on Classifying Fast-acting and Slow-acting Antimalarial Agents Based on Time of Action and Target Organelle of Plasmodium sp

The clinical resistance towards malarial parasites has rendered many antimalarials ineffective, likely due to a lack of understanding of time of action and stage specificity of all life stages. Therefore, to tackle this problem a more incisive comprehensive analysis of the fast and slow-acting profile of antimalarial agents relating to parasite time-kill kinetics and the target organelle on the progression of blood-stage parasites was carried out. It is evident from numerous findings that drugs targeting food vacuole, nuclear components, and endoplasmic reticulum mainly exhibit a fast-killing phenotype within 24h affecting first-cycle activity. Whereas drugs targeting mitochondria, apicoplast, microtubules, parasite invasion and egress exhibit a largely slow-killing phenotype within 96-120h, affecting second-cycle activity with few exemptions as moderately fast-killing. It is essential to understand the susceptibility of drugs on rings, trophozoites, schizonts, merozoites, and the appearance of organelle at each stage of 48h intraerythrocytic parasite cycle. Therefore, these parameters may facilitate the paradigm for understanding the timing of antimalarials action in deciphering its precise mechanism linked with time. Thus, classifying drugs based on the time of killing may promote designing new combination regimens against varied strains of P. falciparum and evaluating potential clinical resistance.

Structural activity relationship of metallo-aminoquines as a next generation antimalarials

Apicomplexian parasite of the genus Plasmodium is the causative agent of malaria, one of the most devastating, furious and common infectious disease throughout the world. According to the latest World malaria report, there were 229 million cases of malaria in 2019 majorly consisting of children under 5 years of age. Some of known analogues viz. quinine, quinoline-containing compounds have been used for last century in the clinical treatment of malaria. Past few decades have witnessed the emergence of multi-drug resistance (MDR) strains of Plasmodium species to existing antimalarials pressing the need for new drug candidates. For the past few decades bioorganometallic approach to malaria therapy has been introduced which led to the discovery of noval metalcontaining aminoquinolines analogues viz. ferroquine (FQ or 1), Ruthenoquine (RQ or 2) and other related potent metal-analogues. It observed that some metal containing analogues (Fe-, Rh-, Ru-, Re-, Au-, Zn-, Cr-, Pd-, Sn-, Cd-, Ir-, Co-, Cu-, and Mn-aminoquines) were more potent; however, some were equally potent as Chloroquine (CQ) and 1. This is probably due to the intertion of metals in the CQ via various approaches, which might be a very attractive strategy to develop a SAR of novel metal containing antimalarials. Thus, this review aims to summarize the SAR of metal containing aminoquines towards the discovery of potent antimalarial hybrids to provide an insight for rational designs of more effective and less toxic metal containing amoniquines.

Studies of Potency and Efficacy of an Optimized Artemisinin-Quinoline Hybrid against Multiple Stages of the Plasmodium Life Cycle

A recently developed artemisinin-quinoline hybrid, named 163A, has been shown to display potent activity against the asexual blood stage of Plasmodium, the malaria parasite. In this study, we determined its in vitro cytotoxicity to mammalian cells, its potency to suppress P. berghei hepatic infection and to decrease the viability of P. falciparum gametocytes, in addition to determining whether the drug exhibits efficacy of a P. berghei infection in mice. This hybrid compound has a low level of cytotoxicity to mammalian cells and, conversely, a high level of selectivity. It is potent in the prevention of hepatic stage development as well as in killing gametocytes, denoting a potential blockage of malaria transmission. The hybrid presents a potent inhibitory activity for beta-hematin crystal formation, in which subsequent assays revealed that its endoperoxide component undergoes bioactivation by reductive reaction with ferrous heme towards the formation of heme-drug adducts; in parallel, the 7-chloroquinoline component has binding affinity for ferric hemin. Both structural components of the hybrid co-operate to enhance the inhibition of beta-hematin, and this bitopic ligand property is essential for arresting the growth of asexual blood parasites. We demonstrated the in vivo efficacy of the hybrid as an erythrocytic schizonticide agent in comparison to a chloroquine/artemisinin combination therapy. Collectively, the findings suggest that the bitopic property of the hybrid is highly operative on heme detoxification suppression, and this provides compelling evidence for explaining the action of the hybrid on the asexual blood stage. For sporozoite and gametocyte stages, the hybrid conserves the potency typically observed for endoperoxide drugs, and this is possibly achieved due to the redox chemistry of endoperoxide components with ferrous heme.

In Vitro Antiplasmodial, Heme Polymerization, and Cytotoxicity of Hydroxyxanthone Derivatives

The previous study showed that xanthone had antiplasmodial activity. Xanthone, with additional hydroxyl groups, was synthesized to increase its antiplasmodial activity. One of the strategies to evaluate a compound that can be developed into an antimalarial drug is by testing its mechanism in inhibiting heme polymerization. In acidic condition, hematin can be polymerized to β-hematin in vitro, which is analog with hemozoin in Plasmodium. This study was conducted to evaluate the antiplasmodial activity of hydroxyxanthone derivative compounds on two strains of Plasmodium falciparum 3D-7 and FCR-3, to assess inhibition of heme polymerization activity and determine the selectivity of hydroxyxanthone derivative compounds. The antiplasmodial activity of each compound was tested on Plasmodium falciparum 3D-7 and FCR-3 with 72 hours incubation period, triplicated in three replications with the microscopic method. The compound that showed the best antiplasmodial activity underwent flow cytometry assay. Heme polymerization inhibition test was performed using the in vitro heme polymerization inhibition activity (HPIA) assay. The antiplasmodial activity and heme polymerization inhibition activity were expressed as the 50% inhibitory concentration (IC50). In vitro cytotoxicity was tested using the MTT assay method on Vero cell lines to determine its selectivity index. The results showed that among 5-hydroxyxanthone derivative compounds, the 1,6,8-trihydroxyxanthone had the best in vitro antiplasmodial activity on both 3D-7 and FCR-3 Plasmodium falciparum strains with IC50 values of 6.10 ± 2.01 and 6.76 ± 2.38 μM, respectively. The 1,6,8-trihydroxyxanthone showed inhibition activity of heme polymerization with IC50 value of 2.854 mM and showed the high selectivity with selectivity index of 502.2-556.54. In conclusion, among 5-hydroxyxanthone derivatives tested, the 1,6,8-trihydroxyxantone showed the best antiplasmodial activity and has heme polymerization inhibition activity and high selectivity.

A Novel Hybrid of Chloroquine and Primaquine Linked by Gold(I): Multitarget and Multiphase Antiplasmodial Agent

Plasmodium parasites kill 435 000 people around the world every year due to unavailable vaccines, a limited arsenal of antimalarial drugs, delayed treatment, and the reduced clinical effectiveness of current practices caused by drug resistance. Therefore, there is an urgent need to discover and develop new antiplasmodial candidates. In this work, we present a novel strategy to develop a multitarget metallic hybrid antimalarial agent with possible dual efficacy in both sexual and asexual erythrocytic stages. A hybrid of antimalarial drugs (chloroquine and primaquine) linked by gold(I) was synthesized and characterized by spectroscopic and analytical techniques. The CQPQ-gold(I) hybrid molecule affects essential parasite targets, it inhibits β-hematin formation and interacts moderately with the DNA minor groove. Its interaction with PfTrxR was also examined in computational modeling studies. The CQPQ-gold(I) hybrid displayed an excellent in vitro antimalarial activity against the blood-stage of Plasmodium falciparum and liver-stage of Plasmodium berghei and efficacy in vivo against P. berghei, thereby demonstrating its multiple-stage antiplasmodial activity. This metallic hybrid is a promising chemotherapeutic agent that could act in the treatment, prevention, and transmission of malaria.

Recent Advances in the Biological Investigation of Organometallic Platinum-Group Metal (Ir, Ru, Rh, Os, Pd, Pt) Complexes as Antimalarial Agents

In the face of the recent pandemic and emergence of infectious diseases of viral origin, research on parasitic diseases such as malaria continues to remain critical and innovative methods are required to target the rising widespread resistance that renders conventional therapies unusable. The prolific use of auxiliary metallo-fragments has augmented the search for novel drug regimens in an attempt to combat rising resistance. The development of organometallic compounds (those containing metal-carbon bonds) as antimalarial drugs has been exemplified by the clinical development of ferroquine in the nascent field of Bioorganometallic Chemistry. With their inherent physicochemical properties, organometallic complexes can modulate the discipline of chemical biology by proffering different modes of action and targeting various enzymes. With the beneficiation of platinum group metals (PGMs) in mind, this review aims to describe recent studies on the antimalarial activity of PGM-based organometallic complexes. This review does not provide an exhaustive coverage of the literature but focusses on recent advances of bioorganometallic antimalarial drug leads, including a brief mention of recent trends comprising interactions with biomolecules such as heme and intracellular catalysis. This resource can be used in parallel with complementary reviews on metal-based complexes tested against malaria.

SARS-CoV-2 and mitochondrial health: implications of lifestyle and ageing

Infection with SARs-COV-2 displays increasing fatality with age and underlying co-morbidity, in particular, with markers of the metabolic syndrome and diabetes, which seems to be associated with a "cytokine storm" and an altered immune response. This suggests that a key contributory factor could be immunosenescence that is both age-related and lifestyle-induced. As the immune system itself is heavily reliant on mitochondrial function, then maintaining a healthy mitochondrial system may play a key role in resisting the virus, both directly, and indirectly by ensuring a good vaccine response. Furthermore, as viruses in general, and quite possibly this new virus, have also evolved to modulate immunometabolism and thus mitochondrial function to ensure their replication, this could further stress cellular bioenergetics. Unlike most sedentary modern humans, one of the natural hosts for the virus, the bat, has to "exercise" regularly to find food, which continually provides a powerful adaptive stimulus to maintain functional muscle and mitochondria. In effect the bat is exposed to regular hormetic stimuli, which could provide clues on how to resist this virus. In this paper we review the data that might support the idea that mitochondrial health, induced by a healthy lifestyle, could be a key factor in resisting the virus, and for those people who are perhaps not in optimal health, treatments that could support mitochondrial function might be pivotal to their long-term recovery.

Copper-catalyzed synthesis of aminoquinolines from β-(2-aminophenyl)-α,β-ynones using DMF as dual synthon

A new and efficient method has been developed for the synthesis of 4-aminoquinoline through aerobic Cu(i)-catalyzed cyclization of β-(2-aminophenyl)-α,β-ynones. Under the optimized conditions, DMF could serve as a methine source to introduce C2 carbon and a nitrogen source to incorporate amino functionality in the 4th position. Mechanistic studies using 13C- and DMF-d7 revealed that the methine group was derived from a methyl substituent.

Synthesis, crystal structures, DFT studies, antibacterial assays and interaction assessments with biomolecules of new platinum(ii) complexes with adamantane derivatives

Synthesis, crystal structures and antibacterial activities of new Pt(ii) complexes with adamantane derivatives are presented in this article.

Current scenario of ferrocene-containing hybrids for antimalarial activity

Hybrid molecules have the potential to enhance the efficacy against both drug-sensitive and drug-resistant organisms, and Ferroquine, a ferrocene hybrid, has demonstrated great potency in clinical trials against both drug-sensitive and drug-resistant malaria. Accordingly, hybridization of ferrocene with other antimalarial pharmacophores represents a promising strategy to develop novel antimalarial candidates. This work attempts to systematically review the recent study of ferrocene hybrids in the design and development of antimalarial agents, and the structure-activity relationship (SAR) is also discussed to provide an insight for rational design of more effective antibacterial candidates.

Antiparasitic activity and ultrastructural alterations provoked by organoruthenium complexes against Leishmania amazonensis

New organoruthenium complexes were synthetized, characterized and evaluated to inhibit the proliferation of the Leishmania amazonensis parasite.

A review on diverse heterocyclic compounds as the privileged scaffolds in antimalarial drug discovery

The upward extend of malaria collectively with the emergence of resistance against predictable drugs has put enormous pressure on public health systems to introduce new malaria treatments. Heterocycles play an important role in the design and discovery of new malaria active compounds. Heterocyclic compounds have attracted significant attention for malaria treatment because of simplicity of parallelization and the examining power with regard to chemical space. Introduction of a variety of heterocyclic compounds have enabled to maintain the high levels of antimalarial potency observed for other more lipophilic analogues whilst improving the solubility and the oral bioavailability in pre-clinical species. In this review, we present an overview of recent literature to provide imminent into the applications of different heterocyclic scaffolds in fighting against malaria.

Synthesis, characterization and biological application of 5-quinoline 1,3,5-trisubstituted pyrazole based platinum(ii) complexes

Square planar mononuclear platinum(ii) complexes were synthesized in the presence of neutral bidentate heterocyclic (5-quinoline 1,3,5-tri-substituted pyrazole scaffold) ligands and K₂PtCl₄ salt. The synthesized compounds were characterized by micro-elemental analysis, FT-IR, UV-vis, ¹H NMR, ¹³C NMR, TGA, mass spectrometry and molar conductivity. Their biological activities were investigated by in vitro brine shrimp lethality bioassay, in vitro antimicrobial study against five different pathogens, in vivo cellular level cytotoxicity against Schizosaccharomyces pombe cells, and in vitro anti-proliferation assay. The binding constant K_sv, K_b, K_a values of the complexes were determined by DNA interaction studies. The gel electrophoresis assay was carried out to examine the effect of the complexes on the DNA nuclease of pUC19 plasmid DNA. The docking energies of the ligands (L¹-L⁵ ) and complexes (I-V) were observed in the range of -265.14 to -284.33 kJ mol^-1. The synthesized Pt(ii) complexes (I-V) were screened against the MCF-7 (human breast adenocarcinoma) and HCT-116 (human colon carcinoma) cancer cell lines.