Antimalarial chemotherapeutic peroxides: artemisinin, yingzhaosu A and related compounds

Recent advances in the synthesis and antimalarial activity of 1,2,4-trioxanes

The increasing resistance of various malarial parasite strains to drugs has made the production of a new, rapid-acting, and efficient antimalarial drug more necessary, as the demand for such drugs is growing rapidly. As a major global health concern, various methods have been implemented to address the problem of drug resistance, including the hybrid drug concept, combination therapy, the development of analogues of existing medicines, and the use of drug resistance reversal agents. Artemisinin and its derivatives are currently used against multidrug- resistant P. falciparum species. However, due to its natural origin, its use has been limited by its scarcity in natural resources. As a result, finding a substitute becomes more crucial, and the peroxide group in artemisinin, responsible for the drugs biological action in the form of 1,2,4-trioxane, may hold the key to resolving this issue. The literature suggests that 1,2,4-trioxanes have the potential to become an alternative to current malaria drugs, as highlighted in this review. This is why 1,2,4-trioxanes and their derivatives have been synthesized on a large scale worldwide, as they have shown promising antimalarial activity in vivo and in vitro against Plasmodium species. Consequently, the search for a more convenient, environment friendly, sustainable, efficient, and effective synthetic pathway for the synthesis of 1,2,4-trioxanes continues. The aim of this work is to provide a comprehensive analysis of the synthesis and mechanism of action of 1,2,4-trioxanes. This systematic review highlights the most recent summaries of derivatives of 1,2,4-trioxane compounds and dimers with potential antimalarial activity from January 1988 to 2023.

Electrochemical Generation of Peroxy Radicals and Subsequent Peroxidation of 1,3-Dicarbonyls in an Undivided Cell

The generation of peroxy radicals from hydroperoxides with subsequent selective peroxidation of 1,3-dicarbonyls in an undivided electrochemical cell under constant current conditions is reported. The method provides a variety of peroxy-containing barbituric acids and 4-hydroxy-2(5H)-furanones with yields of up to 74%. Only the combination of anodic and cathodic processes provides efficient peroxidation by generating a set of alkoxy and peroxy radicals. NaNO3 acts as both an electrolyte and a redox mediator of radical reactions.

An overview on the antimalarial activity of 1,2,4-trioxanes, 1,2,4-trioxolanes and 1,2,4,5-tetraoxanes

The demand for novel, fast-acting, and effective antimalarial medications is increasing exponentially. Multidrug resistant forms of malarial parasites, which are rapidly spreading, pose a serious threat to global health. Drug resistance has been addressed using a variety of strategies, such as targeted therapies, the hybrid drug idea, the development of advanced analogues of pre-existing drugs, and the hybrid model of resistant strains control mechanisms. Additionally, the demand for discovering new potent drugs grows due to the prolonged life cycle of conventional therapy brought on by the emergence of resistant strains and ongoing changes in existing therapies. The 1,2,4-trioxane ring system in artemisinin (ART) is the most significant endoperoxide structural scaffold and is thought to be the key pharmacophoric moiety required for the pharmacodynamic potential of endoperoxide-based antimalarials. Several derivatives of artemisinin have also been found as potential treatments for multidrug-resistant strain in this area. Many 1,2,4-trioxanes, 1,2,4-trioxolanes, and 1,2,4,5-tetraoxanes derivatives have been synthesised as a result, and many of these have shown promise antimalarial activity both in vivo and in vitro against Plasmodium parasites. As a consequence, efforts to develop a functionally straight-forward, less expensive, and vastly more effective synthetic pathway to trioxanes continue. This study aims to give a thorough examination of the biological properties and mode of action of endoperoxide compounds derived from 1,2,4-trioxane-based functional scaffolds. The present system of 1,2,4-trioxane, 1,2,4-trioxolane, and 1,2,4,5-tetraoxane compounds and dimers with potentially antimalarial activity will be highlighted in this systematic review (January 1963-December 2022).

Synthesis and antimalarial activity of amide and ester conjugates of siderophores and ozonides

Despite advances in chemotherapeutic interventions for the treatment of malaria, there is a continuing need for the development of new antimalarial agents. Previous studies indicated that co-administration of chloroquine with antioxidants such as the iron chelator deferoxamine (DFO) prevented the development of persistent cognitive damage in surrogate models of cerebral malaria. The work described herein reports the syntheses and antimalarial activities of covalent conjugates of both natural (siderophores) and artificial iron chelators, namely DFO, ferricrocin and ICL-670, with antimalarial 1,2,4-trioxolanes (ozonides). All of the synthesized conjugates had potent antimalarial activities against the in vitro cultures of drug resistant and drug sensitive strains of Plasmodium falciparum. The work described herein provides the basis for future development of covalent combination of iron chelators and antimalarial chemotherapeutic agents for the treatment of cerebral malaria.

Advocacy for the Medicinal Plant Artabotrys hexapetalus (Yingzhao) and Antimalarial Yingzhaosu Endoperoxides

The medicinal plant Artabotrys hexapetalus (synonyms: A.uncinatus and A. odoratissimus) is known as yingzhao in Chinese. Extracts of the plant have long been used in Asian folk medicine to treat various symptoms and diseases, including fevers, microbial infections, ulcers, hepatic disorders and other health problems. In particular, extracts from the roots and fruits of the plant are used for treating malaria. Numerous bioactive natural products have been isolated from the plant, mainly aporphine (artabonatines, artacinatine) and benzylisoquinoline (hexapetalines) alkaloids, terpenoids (artaboterpenoids), flavonoids (artabotrysides), butanolides (uncinine, artapetalins) and a small series of endoperoxides known as yingzhaosu A-to-D. These natural products confer antioxidant, anti-inflammatory and antiproliferative properties to the plant extracts. The lead compound yingzhaosu A displays marked activities against the malaria parasites Plasmodium falciparum and P. berghei. Total syntheses have been developed to access yingzhaosu compounds and analogues, such as the potent compound C14-epi-yingzhaosu A and simpler molecules with a dioxane unit. The mechanism of action of yingzhaosu A points to an iron(II)-induced degradation leading to the formation of two alkylating species, an unsaturated ketone and a cyclohexyl radical, which can then react with vital parasitic proteins. A bioreductive activation of yingzhaosu A endoperoxide can also occur with the heme iron complex. The mechanism of action of yingzhaosu endoperoxides is discussed, to promote further chemical and pharmacological studies of these neglected, but highly interesting bioactive compounds. Yingzhaosu A/C represent useful templates for designing novel antimalarial drugs.

Novel hydrazone derivatives of N-amino-11-azaartemisinin with high order of antimalarial activity against multidrug-resistant Plasmodium yoelii nigeriensis in Swiss mice via intramuscular route

Novel hydrazone derivatives 10a-m were prepared from N-Amino-11-azaartemisinin (9) and screened for their antimalarial activity by oral and intramuscular (i.m.) routes against multidrug-resistant Plasmodium yoelii in Swiss mice model. Several of the hydrazone derivatives showed higher order of antimalarial activity. Compounds 10b, 10g, 10m provided 100% protection to the infected mice at the dose of 24 mg/kg × 4 days via oral route. Fluorenone based hydrazone 10m the most active compound of the series, provided 100% protection at the dose of 6 mg/kg × 4 days via intramuscular route and also provided 100% protection at the dose of 12 mg/kg × 4 days via oral route. While artemisinin gave 100% protection at 48 mg/kg × 4 days and only 60% protection at 24 mg/kg × 4 days via intramuscular (i.m.) route. Compound 10m found to be four-fold more active than artemisinin via intramuscular route.

Reduction of the Double Bond of 6-Arylvinyl-1,2,4-trioxanes Leads to a Remarkable Increase in Their Antimalarial Activity against Multidrug-Resistant Plasmodium yoelii nigeriensis in a Swiss Mice Model

Novel 6-arylethyl-1,2,4-trioxanes6a-i and 7a-i are easily accessible in one step from the diimide reduction of 6-arylvinyl-1,2,4-trioxanes 5a-i. All of these new trioxanes were assessed for their oral antimalarial activity against multidrug-resistant Plasmodium yoelii nigeriensis in a Swiss mice model. Most of the saturated trioxanes 6c, 6f, 6g, 6h, and 6i, the active compounds of the series, provided 100% protection to the malaria-infected mice at a dose of 24 mg/kg × 4 days. Further, trioxane 6i, the most active compound of the series, also showed 100% protection even at a dose of 12 mg/kg × 4 days and 20% protection at a dose of 6 mg/kg × 4 days. In this model, β-arteether provided 100% protection at a dose of 48 mg/kg × 4 days and only 20% protection at a dose of 24 mg/kg × 4 days via the oral route, which was found to exhibit 4-fold antimalarial activity compared with the currently used drug β-arteether.

Immunomolecular evaluation of dihydroartemisinin effects on apoptosis in chronic lymphocytic leukemia cell lines

INTRODUCTION

Dihydroartemisinin (DHA), a semi-synthetic derivative of artemisinin, has recently shown to induce apoptosis in many types of cancer cells. In this study, we aimed to determine the effects of DHA on apoptosis in human chronic lymphocytic leukemia (CLL) cell lines.

METHODS

The cells were treated separately and combined by DHA and Fludurabine (FLU) during 24, 48 and 72 hours. The cell viabilities determined by XTT method. Following separate and combined treatment of IC50 concentrations of DHA and FLU to the cells during 24 hours, the cells were analyzed by flow cytometry to determine the effects on apopotis staining with AnnexinV FITC and PI. mRNA and protein expression levels of TCTP, Mcl-1, Bcl-2, Bax and Caspase-3 were analyzed to find out the molecular mechanisms of apoptosis by using quantitative real-time PCR and flow cytometric methods.

RESULTS

Treatment with DHA alone or in combination with FLU induced apoptosis in a dose dependent manner in CLL cells. DHA alone was more effective than FLU alone or combined treatment with DHA and FLU. Our results suggest that Bcl-2 protein family member Bax was active in the apoptotic response of CLL cells after DHA treatment. Moreover, the apoptotic response induced by DHA was independent from the p53 mutation status of the CLL cells.

CONCLUSION

DHA might be a potential anti-cancer therapeutic for CLL.

A Comparative Review on Current and Future Drug Targets Against Bacteria & Malaria

Long before the discovery of drugs like 'antibiotic and anti-parasitic drugs', the infectious diseases caused by pathogenic bacteria and parasites remain as one of the major causes of morbidity and mortality in developing and underdeveloped countries. The phenomenon by which the organism exerts resistance against two or more structurally unrelated drugs is called multidrug resistance (MDR) and its emergence has further complicated the treatment scenario of infectious diseases. Resistance towards the available set of treatment options and poor pipeline of novel drug development puts an alarming situation. A universal goal in the post-genomic era is to identify novel targets/drugs for various life-threatening diseases caused by such pathogens. This review is conceptualized in the backdrop of drug resistance in two major pathogens i.e. "Pseudomonas aeruginosa" and "Plasmodium falciparum". In this review, the available targets and key mechanisms of resistance of these pathogens have been discussed in detail. An attempt has also been made to analyze the common drug targets of bacteria and malaria parasite to overcome the current drug resistance scenario. The solution is also hypothesized in terms of a present pipeline of drugs and efforts made by scientific community.

Magnetotactic Bacteria Accumulate a Large Pool of Iron Distinct from Their Magnetite Crystals

Magnetotactic bacteria (MTB) produce iron-based intracellular magnetic crystals. They represent a model system for studying iron homeostasis and biomineralization in microorganisms. MTB sequester a large amount of iron in their crystals and have thus been proposed to significantly impact the iron biogeochemical cycle. Several studies proposed that MTB could also accumulate iron in a reservoir distinct from their crystals. Here, we present a chemical and magnetic methodology for quantifying the iron pools in the magnetotactic strain AMB-1. Results showed that most iron is not contained in crystals. We then adapted protocols for the fluorescent Fe(II) detection in bacteria and showed that iron could be detected outside crystals using fluorescence assays. This work suggests a more complex picture for iron homeostasis in MTB than previously thought. Because iron speciation controls its fate in the environment, our results also provide important insights into the geochemical impact of MTB.

Magnetotactic bacteria (MTB) are ubiquitous aquatic microorganisms that form intracellular nanoparticles of magnetite (Fe₃O₄) or greigite (Fe₃S₄) in a genetically controlled manner. Magnetite and greigite synthesis requires MTB to transport a large amount of iron from the environment. Most intracellular iron was proposed to be contained within the crystals. However, recent mass spectrometry studies suggest that MTB may contain a large amount of iron that is not precipitated in crystals. Here, we attempted to resolve these discrepancies by performing chemical and magnetic assays to quantify the different iron pools in the magnetite-forming strain Magnetospirillum magneticum AMB-1, as well as in mutant strains showing defects in crystal precipitation, cultivated at various iron concentrations. All results show that magnetite represents at most 30% of the total intracellular iron under our experimental conditions and even less in the mutant strains. We further examined the iron speciation and subcellular localization in AMB-1 using the fluorescent indicator FIP-1, which was designed for the detection of labile Fe(II). Staining with this probe suggests that unmineralized reduced iron is found in the cytoplasm and associated with magnetosomes. Our results demonstrate that, under our experimental conditions, AMB-1 is able to accumulate a large pool of iron distinct from magnetite. Finally, we discuss the biochemical and geochemical implications of these results.

IMPORTANCE Magnetotactic bacteria (MTB) produce iron-based intracellular magnetic crystals. They represent a model system for studying iron homeostasis and biomineralization in microorganisms. MTB sequester a large amount of iron in their crystals and have thus been proposed to significantly impact the iron biogeochemical cycle. Several studies proposed that MTB could also accumulate iron in a reservoir distinct from their crystals. Here, we present a chemical and magnetic methodology for quantifying the iron pools in the magnetotactic strain AMB-1. Results showed that most iron is not contained in crystals. We then adapted protocols for the fluorescent Fe(II) detection in bacteria and showed that iron could be detected outside crystals using fluorescence assays. This work suggests a more complex picture for iron homeostasis in MTB than previously thought. Because iron speciation controls its fate in the environment, our results also provide important insights into the geochemical impact of MTB.

Natural Products as Sources of Antimalarial Drugs: Ethnobotanical and Ethnopharmacological Studies

MATERIALS AND METHODS

For this study, relevant information was procured from the inhabitants via a structured questionnaire to procure the general knowledge of antimalarial medicinal plants. Results and Discussion. A total of 90 interviewees (44 men and 46 women) were involved in this survey. A total of 59 medicinal species were identified, which were dispersed in 33 families (Asteraceae (6), Apocynaceae (5), Anacardiaceae, Annonaceae, Fabaceae, Malvaceae, Meliaceae, Poaceae, and Rubiaceae (3 each), Phyllanthaceae (2)) totaling 49% of the cited species. The most cited plants are Azadirachta indica (42), Mangifera indica (38), Carica papaya (28), Cymbopogon citratus (27), Cassia fistula (15), Morinda lucida (14), Anacardium occidentale and Vernonia amygdalina (13 each), Helianthus annuus (11), Enantia chlorantha (10), and Moringa oleifera (9) A total of 105 citations were recorded for the plant parts used (leaf (46), bark (17), fruits (9), root (9), latex (11), stem (11), and inflorescence (2)) while decoction (59%), maceration (25%), infusion (9%), and exudation (7%) were the methods of preparation. Use Values (UVs) of 0.47 to 0.11 were recorded for the frequently used antimalarial plants. The Efficiency Levels (ELs) of 11 different medicinal plants stated by the respondents were Azadirachta indica, Cassia fistula and Morinda lucida (12), Chromolaena odorata (10), Mangifera indica, Enantia chlorantha and Helianthus annuus (8), Cymbopogon citratus (7), Gossypium arboretum (4), Landolphia dulcis (3), and Aloe vera (2) Cocos nucifera, Curcuma longa, Forkia biglobosa, and Musa acuminate are mentioned for the first time in the study area with little or no reported antiplasmodial activities.

CONCLUSION

The study appraised the commonly used antimalarial plants in the study areas. Therefore, commitment to scientifically explore the bioactive compounds, antimalarial potential and toxicological profile of these plants is inevitable as they could lead to novel natural products for effective malaria therapy.

Peroxycarbenium Ions as the "Gatekeepers" in Reaction Design: Assistance from Inverse Alpha-Effect in Three-Component β-Alkoxy-β-peroxylactones Synthesis

Stereoelectronic interactions control reactivity of peroxycarbenium cations, the key intermediates in (per)oxidation chemistry. Computational analysis suggests that alcohol involvement as a third component in the carbonyl/peroxide reactions remained invisible due to the absence of sufficiently deep kinetic traps needed to prevent the escape of mixed alcohol/peroxide products to the more stable bisperoxides. Synthesis of β-alkoxy-β-peroxylactones, a new type of organic peroxides, was accomplished by interrupting a thermodynamically driven peroxidation cascade. The higher energy β-alkoxy-β-peroxylactones do not transform into the more stable bisperoxides due to the stereoelectronically imposed instability of a cyclic peroxycarbenium intermediate as a consequence of amplified inverse alpha-effect. The practical consequence of this fundamental finding is the first three-component cyclization/condensation of β-ketoesters, H₂ O₂ , and alcohols that provides β-alkoxy-β-peroxylactones in 15-80 % yields.

Interactions between artemisinin derivatives and P-glycoprotein

BACKGROUND

Artemisinin was isolated and identified in 1972, which was the starting point for a new era in antimalarial drug therapy. Furthermore, numerous studies have demonstrated that artemisinin and its derivatives exhibit considerable anticancer activity both in vitro, in vivo, and even in clinical Phase I/II trials. P-glycoprotein (P-gp) mediated multi-drug resistance (MDR) is one of the most serious causes of chemotherapy failure in cancer treatment. Interestingly, many artemisinin derivatives exhibit excellent ability to overcome P-gp mediated MDR and even show collateral sensitivity against MDR cancer cells. Furthermore, some artemisinin derivatives show P-gp-mediated MDR reversal activity. Therefore, the interaction between P-gp and artemisinin derivatives is important to develop novel combination treatment protocols with artemisinin derivatives and established anticancer drugs that are P-gp substrates.

PURPOSE

This systematic review provides an updated overview on the interaction between artemisinin derivatives and P-gp and the effect of artemisinin derivatives on the P-gp expression level.

RESULTS

Artemisinin derivatives exhibit multi-specific interactions with P-gp. The currently used artemisinin derivatives are not transported by P-gp. However, some of novel synthetized artemisinin derivatives exhibit P-gp substrate properties. Furthermore, many artemisinin derivatives act as P-gp inhibitors, which exhibit the potential to reverse MDR towards clinically used anticancer drugs.

CONCLUSION

Therefore, studies on the interaction between artemisinin derivatives and P-gp provide important information for the development of novel anti-cancer artemisinin derivatives to reverse P-gp mediated MDR and for the design of rational artemisinin-based combination therapies against cancer.

Non-nitrogenous Plant-derived Constituents with Antiplasmodial Activity

The paper is a compilation of the studies reported in the literature concerning non-nitrogenous natural constituents that have shown antiplasmodial activity and aims to provide a basis for further in vivo studies as well as for clinical trials to develop new antimalarial agents. Due to the increasingly unsatisfactory outcomes for N-heterocyclic drugs, coupled with the rising incidence of the deadly falciparum malaria, the advent of non-nitrogenous lead compounds is timely, signaling a new era of antimalarial chemotherapy. Currently a few non-nitrogenous molecules are used in therapy, but many promising molecules of plant origin are under study, such as peroxide sesquiterpenes, quinoid triterpenes, quassinoids, gallic acid derivatives, lignans, flavonoids and biflavonoids, xanthones, naphthoquinones and phenylanthraquinones. Many of these constituents are isolated from plants used traditionally to treat malaria and fever. Ethnopharmacology can still be considered as a rich source of lead molecules.

Fluorescent probes for the detection of catalytic Fe(II) ion

Iron (Fe) is the most abundant redox-active metal ion in the human body, and its redox-active inter-convertible multiple oxidation states contributes to numerous essential biological processes. Moreover, iron overload can potentially cause cellular damage and death, as wel as numerous diseases through the aberrant production of highly reactive oxidative species (hROS). Protein-free or weakly-protein-bound Fe ions play a pivotal role as catalytic reactants of the Fenton reaction. In this reaction, hROS, such as hydroxyl radicals and high valent-iron-oxo species, are generated by a reaction between hydrogen peroxide and Fe(II), which is re-generated through reduction using abundant intracellular reductants, such as glutathione. This results in the catalytic evolution of hROS. Thus, selective detection of the catalytic Fe(II) in the living systems can explain both of the pathological and physiological functions of Fe(II). Written from the perspective of their modes of actions, this paper presents recent advances in the development of fluorescent and bioluminescent probes that can selectively detect catalytic Fe(II) together with their biological applications.

Activity-based sensing fluorescent probes for iron in biological systems

Iron is an essential nutrient for life, and its capacity to cycle between different oxidation states is required for processes spanning oxygen transport and respiration to nucleotide synthesis and epigenetic regulation. However, this same redox ability also makes iron, if not regulated properly, a potentially dangerous toxin that can trigger oxidative stress and damage. New methods that enable monitoring of iron in living biological systems, particularly in labile Fe²⁺ forms, can help identify its contributions to physiology, aging, and disease. In this review, we summarize recent developments in activity-based sensing (ABS) probes for fluorescence Fe²⁺ detection.

A Novel Tumor-Activated Prodrug Strategy Targeting Ferrous Iron Is Effective in Multiple Preclinical Cancer Models

Here we describe a new approach for tumor targeting in which augmented concentrations of Fe(II) in cancer cells and/or the tumor microenvironment triggers drug release from an Fe(II)-reactive prodrug conjugate. The 1,2,4-trioxolane scaffold developed to enable this approach can in principle be applied to a broad range of cancer therapeutics and is illustrated here with Fe(II)-targeted forms of a microtubule toxin and a duocarmycin-class DNA-alkylating agent. We show that the intrinsic reactivity/toxicity of the duocarmycin analog is masked in the conjugated form and this greatly reduced toxicity in mice. This in turn permitted elevated dosing levels, leading to higher systemic exposure and a significantly improved response in tumor xenograft models. Overall our results suggest that Fe(II)-dependent drug delivery via trioxolane conjugates could have significant utility in expanding the therapeutic index of a range of clinical and preclinical stage cancer chemotherapeutics.

An Endoperoxide Reactivity-Based FRET Probe for Ratiometric Fluorescence Imaging of Labile Iron Pools in Living Cells

Iron is essential for sustaining life, as its ability to cycle between multiple oxidation states is critical for catalyzing chemical transformations in biological systems. However, without proper regulation, this same redox capacity can trigger oxidative stress events that contribute to aging along with diseases ranging from cancer to cardiovascular and neurodegenerative disorders. Despite its importance, methods for monitoring biological iron bound weakly to cellular ligands−the labile iron pool−to generate a response that preserves spatial and temporal information remain limited, owing to the potent fluorescence quenching ability of iron. We report the design, synthesis, and biological evaluation of FRET Iron Probe 1 (FIP-1), a reactivity-based probe that enables ratiometric fluorescence imaging of labile iron pools in living systems. Inspired by antimalarial natural products and related therapeutics, FIP-1 links two fluorophores (fluorescein and Cy3) through an Fe(II)-cleavable endoperoxide bridge, where Fe(II)-triggered peroxide cleavage leads to a decrease in fluorescence resonance energy transfer (FRET) from the fluorescein donor to Cy3 acceptor by splitting these two dyes into separate fragments. FIP-1 responds to Fe(II) in aqueous buffer with selectivity over competing metal ions and is capable of detecting changes in labile iron pools within living cells with iron supplementation and/or depletion. Moreover, application of FIP-1 to a model of ferroptosis reveals a change in labile iron pools during this form of cell death, providing a starting point to study iron signaling in living systems.

A reactivity-based probe of the intracellular labile ferrous iron pool

Improved methods for studying intracellular reactive iron(II) are of significant interest for studies of iron metabolism and disease relevant changes in iron homeostasis. Here we describe a highly-selective reactivity-based probe in which Fenton-type reaction with intracellular labile iron(II) leads to unmasking of the aminonucleoside puromycin. Puromycin leaves a permanent and dose-dependent mark on treated cells that can be detected with high sensitivity and precision using the high-content, plate-based immunofluorescence assay described. Using this new probe and screening approach, we detected alteration of cellular labile iron(II) in response extracellular iron conditioning, overexpression of iron storage and/or export proteins, and post-translational regulation of iron export. Finally, we utilized this new tool to demonstrate the presence of augmented labile iron(II) pools in cancer cells as compared to non-tumorigenic cells.

Artemisinin Represses Telomerase Subunits and Induces Apoptosis in HPV-39 Infected Human Cervical Cancer Cells

Artemisinin, a plant-derived antimalarial drug with relatively low toxicity on normal cells in humans, has selective anticancer activities in various types of cancers, both in vitro and in vivo. In the present study, we have investigated the anticancer effects of artemisinin in human cervical cancer cells, with special emphasis on its role in inducing apoptosis and repressing cell proliferation by inhibiting the telomerase subunits, ERα which is essential for maintenance of the cervix, and downstream components like VEGF, which is known to activate angiogenesis. Effects of artemisinin on apoptosis of ME-180 cells were measured by flow cytometry, DAPI, and annexin V staining. Expression of genes and proteins related to cell proliferation and apoptosis was quantified both at the transcriptional and translational levels by semi-quantitative RT-PCR and western blot analysis, respectively. Our findings demonstrated that artemisinin significantly downregulated the expression of ERα and its downstream component, VEGF. Antiproliferative activity was also supported by decreased telomerase activity and reduced expression of hTR and hTERT subunits. Additionally, artemisinin reduced the expression of the HPV-39 viral E6 and E7 components. Artemisinin-induced apoptosis was confirmed by FACS, nuclear chromatin condensation, annexin V staining. Increased expression of p53 with concomitant decrease in expression of the p53 inhibitor Mdm2 further supported that artemisinin-induced apoptosis was p53-dependent. The results clearly indicate that artemisinin induces antiproliferative and proapoptotic effects in HPV-39-infected ME-180 cells, and warrants further trial as an effective anticancer drug.

Synthesis and antimalarial activity of novel bicyclic and tricyclic aza-peroxides

Bicyclic and tricyclic aza-peroxides were synthesized and assessed for theirin vitroandin vivoantimalarial activities againstPlasmodium falciparum(3D7 strain) andPlasmodium yoelii nigeriensisin Swiss mice by an oral route, respectively.

Stereoelectronic source of the anomalous stability of bis-peroxides

The unusual stability of bis- and tris-peroxides contradicts the conventional wisdom - some of them can melt without decomposition at temperatures exceeding 100 °C. In this work, we disclose a stabilizing stereoelectronic effect that two peroxide groups can exert on each other. This stabilization originates from strong anomeric nO → σ*CO interactions that are absent in mono-peroxides but reintroduced in molecules where two peroxide moieties are separated by a CH2 group. Furthermore, such effects can be induced by other σ-acceptors and amplified by structural constraints imposed by cyclic and bicyclic frameworks.

Arteether nanoemulsion for enhanced efficacy against Plasmodium yoelii nigeriensis malaria: an approach by enhanced bioavailability

The present work is focused on the preparation of nanoemulsions (NEs) loaded with arteether (ART) for its enhanced efficacy against malaria parasites. ART-NEs have been prepared using high pressure homogenization (HPH) technique with the aim of improving its solubility and thus its bioavailability. ART-NEs were optimized in terms of pressure and number of cycles. Globule size and size distributions were chosen as quality parameters. The maximum drug loading was achieved up to 93 ± 7.4% with globule size 156 ± 10.2 nm and zeta potential of -23.3 ± 3.4 mV. The developed ART-NEs were found to be stable in terms of globule size and size distribution at different pH. The in vitro release profile of the ART-NEs showed 62% drug release within 12h. The percentage cell viability of blank NEs were within acceptable limits. A sensitive assay method for the determination of ART in rat plasma by liquid chromatography-mass spectrometry (LC-MS) was employed after oral administration of ART-NEs. The pharmacokinetic study showed significantly enhanced bioavailability of ART in ART-NE-V. The area under curve (AUC) of ART-NE-V was AUC0-t 1988.411 ± 119.66 h ng/ml which was significantly higher (p<0.05) than ART in ground nut oil (GNO) AUC0-t 671.852 ± 187.05 h ng/ml. The Cmax of ART-NE-V (1506 ± 161.22 ng/ml) was also significantly higher (p<0.05) than ART in GNO (175.2 ± 16.54 ng/ml) and ART given intramuscularly (IM) (278.05 ± 38.59 ng/ml). The ART-NE-V was having significantly high antimalarial efficacy and survival rate of mice giving 80% cure rate at 12.5 mg/kg for 5 days in comparison to 30% cure rate of ART in GNO at the same daily dose and it was also comparable to the 100% cure rate at 12.5 mg/kg for 5 days for ART given intramuscularly. In conclusion ART-NE can be a promising oral delivery system for ART.

In vitro antimalarial activity and molecular modeling studies of novel artemisinin derivatives

Cerebral malaria is a serious and sometimes fatal disease caused by aPlasmodium falciparumparasite that infects a female anopheles mosquito which feeds on humans.

Evaluation of in vitro antimalarial activity of different extracts of Artemisia aucheri Boiss. and A. armeniaca Lam. and fractions of the most potent extracts

Ten extracts with different polarity from two Iranian Artemisia species, A. armeniaca Lam. and A. aucheri Boiss, were screened for their antimalarial properties by in vitro   β-hematin formation assay. Dichloromethane (DCM) extracts of both plants showed significant antimalarial activities with IC₅₀ values of 1.36 ± 0.01 and 1.83 ± 0.03 mg/mL and IC₉₀ values of 2.12 ± 0.04 and 2.62 ± 0.09 mg/mL for A. armeniaca and A. aucheri, respectively. Bioactivity-guided fractionation of DCM extracts of both plants by vacuum liquid chromatography (VLC) over silica gel with solvent mixtures of increasing polarities afforded seven fractions. Two fractions from DCM extract of A. armeniaca and four fractions from DCM extract of A. aucheri showed potent antimalarial activity with reducing IC₅₀ and IC₉₀ values compared to extracts. The most potent fraction belonged to DCM extract of A. armeniaca with IC₅₀ and IC₉₀ values of 0.47 ± 0.006 and 0.71 ± 0.006 mg/mL, respectively.

Advances in nanomedicines for malaria treatment

Malaria is an infectious disease that mainly affects children and pregnant women from tropical countries. The mortality rate of people infected with malaria per year is enormous and became a public health concern. The main factor that has contributed to the success of malaria proliferation is the increased number of drug resistant parasites. To counteract this trend, research has been done in nanotechnology and nanomedicine, for the development of new biocompatible systems capable of incorporating drugs, lowering the resistance progress, contributing for diagnosis, control and treatment of malaria by target delivery. In this review, we discussed the main problems associated with the spread of malaria and the most recent developments in nanomedicine for anti-malarial drug delivery.

Synthesis and antimalarial activity of 3,3-spiroanellated 5,6-disubstituted 1,2,4-trioxanes

Novel 3,3-spiroanellated 5-aryl, 6-arylvinyl-substituted 1,2,4-trioxanes 19-34 have been synthesized and appraised for their antimalarial activity against multidrug-resistant Plasmodium yoelii nigeriensis in Swiss mice by oral route at doses ranging from 96 mg/kg × 4 days to 24 mg/kg × 4 days. The most active compound of the series (compound 25) provided 100% protection at 24 mg/kg × 4 days, and other 1,2,4-trioxanes 22, 26, 27, and 30 also showed promising activity. In this model, β-arteether provided 100 and 20% protection at 48 mg/kg × 4 days and 24 mg/kg × 4 days, respectively, by oral route. Compound 25 displayed a similar in vitro pharmacokinetic profile to that of reference drug β-arteether. The activity results demonstrated the importance of an aryl moiety at the C-5 position on the 1,2,4-trioxane pharmacophore.

Mono, Di and Trifunctional Cyclic Organic Peroxides: The Effect of Substituents and Ring Size on their Thermolysis in 1,4-dioxan

The thermal decomposition reaction of cyclic organic peroxides was studied in 1,4-dioxan at initial concentrations between ~10–4 and 10–2 mol L–1 and at a temperature interval between 100 and 170°C, according to the thermal stability of each compound. The kinetic behaviour observed in all systems studied follows a pseudo first order kinetic law up to at least ~86 % of peroxide conversion. An important substituent effect is operative on the rate constant values and consequently on the activation parameters of the thermal decomposition reaction. The application of different treatments (compensation affect or a statistical treatment) on the kinetic data shows the existence of two sets of cyclic peroxides with comparable kinetic behaviour. Different peroxide–solvent interaction mechanisms can be considered within each series.

A Water-Soluble Polysaccharide from the Fruit Bodies of Bulgaria inquinans (Fries) and Its Anti-Malarial Activity

A water-soluble polysaccharide (BIWS-4b) was purified from the fruit bodies of Bulgaria inquinans (Fries). It is composed of mannose (27.2%), glucose (15.5%) and galactose (57.3%). Its molecular weight was estimated to be 7.4 kDa (polydispersity index, Mw/Mn: 1.35). Structural analyses indicated that BIWS-4b mainly contains (1 → 6)-linked, (1 → 5)-linked and (1 → 5,6)-linked β-Galf units; (1 → 4)-linked and non-reducing terminal β-Glcp units; and (1 → 2)-linked, (1 → 6)-linked, (1 → 2,6)-linked and non-reducing terminal α-Manp units. When examined by the 4-day method and in a prophylactic assay in mice, BIWS-4b exhibited markedly suppressive activity against malaria while enhancing the activity of artesunate. Immunological tests indicated that BIWS-4b significantly enhanced macrophage phagocytosis and splenic lymphocyte proliferation in malaria-bearing mice and normal mice. The anti-malarial activity of BIWS-4b might be intermediated by enhancing immune competence and restoring artesunate-suppressed immune function. Thus, BIWS-4b is a potential adjuvant of anti-malaria drugs.

Potential antimalarials from Nigerian plants: a review

Malaria, caused by parasites of the genus Plasmodium, is one of the leading infectious diseases in many tropical regions, including Nigeria, a West African country where transmission occurs all year round. Many of the inhabitants use plants as remedies against fever and other symptoms of acute malaria, as reported herein. Some of these plants have their antimalarial efficacies scientifically demonstrated and the active compounds isolated with their probable mechanisms of action studied. Medicinal plants are used to treat diseases also where the biodiversity of plants occur in parallel with endemic transmission of malaria. This review focuses on medicinal plants which are used to treat malaria in Nigeria, and on antimalarial testing of extracts and purified compounds from plants. Some show intense activity against malaria parasites in vitro and in experimentally infected mice. The search for new drugs based on plants is important due to the emergence and widespread of chloroquine-resistant and multiple drug-resistant malaria parasites, which require the development of new antimalarials. An acquaintance with antimalarial plants may be a springboard for new phytotherapies that could be affordable to treat malaria, especially among the less privileged native people living in endemic areas of the tropics, mostly at risk of this devastating disease.