Exploration of artemisinin derivatives and synthetic peroxides in antimalarial drug discovery research

Synthesis and Evaluation of Fluorinated Piperazine-Hydroxyethylamine Analogues as Potential Antiplasmodial Candidates

In this manuscript, twenty-one novel fluorinated piperazine-hydroxyethylamine analogues were synthesized and tested against Plasmodium falciparum (Pf). Among tested compounds, two 13 g and 14 g exhibited promising inhibitory activity on Pf3D7 with IC50 values of 0.28 and 0.09 μM, respectively. Neither of the hits exhibited cytotoxicity on HepG2 cells up to 150 μM and Vero cells up to 20 μM. Compounds 13 g and 14 g were also evaluated against chloroquine-resistant PfDd2 and displayed IC50 values of 0.11 and 0.10 μM, respectively. Next, 13 g and 14 g were administered to the Plasmodium berghei mice model at 30 mg/kg intraperitoneally for four consecutive doses, which showed 25 % and 50 % reduction in the parasitemia load, respectively. The efficacy of hits 13 g and 14 g was improved along with mean survival time when administered in combination with artesunate. On liver-stage parasites, compounds 13 g and 14 g showed >80 % inhibition at 1 μM. Compound 14 g was also tested for toxicity in mice at 100 mg/kg dose, which revealed no abnormality in mice organs. Preliminary pharmacokinetic studies of compound 14 g exhibited absorption and maintained a presence in the body for more than six hours.

CYP3A4-mediated metabolism of artemisinin to 10β-hydroxyartemisinin with comparable anti-malarial potency

BACKGROUND

The most widely used anti-malarial drug artemisinin (ART) is metabolized extensively, but the therapeutic capacity of its major metabolite remains unknown. Whether the major metabolite of ART (ART-M) contributes to its antiplasmodial potency was investigated in this study.

METHODS

The metabolite identification and enzyme phenotyping of ART were performed using human liver microsomes (HLMs). The stereostructure of the major metabolite ART-M was elucidated by spectroscopic and X-ray crystallographic analysis. The anti-malarial activity of ART-M against two reference Plasmodium strains (Pf3D7 and PfDd2) was evaluated. The pharmacokinetic profiles of ART and its metabolite ART-M were investigated in healthy Chinese subjects after a recommended two-day oral dose of ART plus piperaquine. Pharmacodynamic parameters based on minimum inhibitory concentration (MIC50) and free plasma concentration were employed to evaluate the therapeutic potency of ART-M, including fAUC0-t/MIC50, fCmax/MIC50 and T > MIC50.

RESULTS

A major metabolite 10β-hydroxyartemisinin (ART-M) was found for ART in human, and CYP3A4/3A5 was the major enzymes responsible for ART 10β-hydroxylation. Compared with ART (MIC50, 10.1 nM against Pf3D7), weaker antiplasmodial activity was found for ART-M (MIC50, 61.4 nM against Pf3D7). However, a 3.5-fold higher maximal free plasma concentration was achieved for ART-M (fCmax, 180.0 nM vs. 51.8 nM for ART). ART-M displayed comparable antiplasmodial potency to ART, in terms of fAUC0-t/MIC50 (12.5 h), fCmax/MIC50 (2.8) and T > MIC50 (5 h).

CONCLUSIONS

The major metabolite 10β-hydroxyartemisinin contributes to the antiplasmodial efficacy of ART, which should be considered when evaluation of ART dosing regimens and/or clinical outcomes.

Antimalarial Mechanisms and Resistance Status of Artemisinin and Its Derivatives

Artemisinin is an endoperoxide sesquiterpene lactone isolated from Artemisia annua and is often used to treat malaria. Artemisinin's peroxide bridge is the key structure behind its antimalarial action. Scientists have created dihydroartemisinin, artemether, artesunate, and other derivatives preserving artemisinin's peroxide bridge to increase its clinical utility value. Artemisinin compounds exhibit excellent efficacy, quick action, and minimal toxicity in malaria treatment and have greatly contributed to malaria control. With the wide and unreasonable application of artemisinin-based medicines, malaria parasites have developed artemisinin resistance, making malaria prevention and control increasingly challenging. Artemisinin-resistant Plasmodium strains have been found in many countries and regions. The mechanisms of antimalarials and artemisinin resistance are not well understood, making malaria prevention and control a serious challenge. Understanding the antimalarial and resistance mechanisms of artemisinin drugs helps develop novel antimalarials and guides the rational application of antimalarials to avoid the spread of resistance, which is conducive to malaria control and elimination efforts. This review will discuss the antimalarial mechanisms and resistance status of artemisinin and its derivatives, which will provide a reference for avoiding drug resistance and the research and development of new antimalarial drugs.

1,2,4,5-Tetraoxane derivatives/hybrids as potent antimalarial endoperoxides: Chronological advancements, structure-activity relationship (SAR) studies and future perspectives

Malaria is a life-threatening disease that affects tropical and subtropical regions worldwide. Various drugs were used to treat malaria, including artemisinin and derivatives, antibiotics (tetracycline, doxycycline), quinolines (chloroquine, amodiaquine), and folate antagonists (sulfadoxine and pyrimethamine). Since the malarial parasites developed drug resistance, there is a need to develop new chemical entities with high efficacy and low toxicity. In this context, 1,2,4,5-tetraoxanes emerged as an essential scaffold and have shown promising antimalarial activity. To improve activity and overcome resistance to various antimalarial drugs; 1,2,4,5-tetraoxanes were fused with various aryl/heteroaryl/alicyclic/spiro moieties (steroid-based 1,2,4,5-tetraoxanes, triazine-based 1,2,4,5-tetraoxanes, aminoquinoline-based 1,2,4,5-tetraoxanes, dispiro-based 1,2,4,5-tetraoxanes, piperidine-based 1,2,4,5-tetraoxanes and diaryl-based 1,2,4,5-tetraoxanes). The present review aims to focus on covering the relevant literature published during the past 30 years (1992-2022). We summarize the most significant in vitro, in vivo results and structure-activity relationship studies of 1,2,4,5-tetraoxane-based hybrids as antimalarial agents. The structural evolution of different hybrids can provide the framework for the future development of 1,2,4,5-tetraoxane-based hybrids to treat malaria.

In vitro and in vivo antiplasmodial activity of a synthetic dihydroartemisinin-eosin B hybrid

With the inexorable prevalence and spread of drug-resistant malaria strains, many efforts have been made to find alternative chemotherapeutic agents. In this regard, scientists have developed the concept of hybridization of two or more active pharmacophores into a single chemical compound, resulting in "antimalarial hybrids." The aim of this study was planned based on the highly synergistic effect of the physical hybrid of dihydroartemisinin (DHA) with eosin B (EB). Therefore, a chemical hybrid of the two compounds (DHA-EB) was synthesized, and its antimalarial activity was investigated in vitro and in vivo. The drug hybrid was fabricated through a propionyl ester linker between DHA and EB. The antiplasmodial activity of the new hybrid was tested in vitro on the blood stages of Plasmodium falciparum (chloroquine-sensitive, 3D7 strain) and also evaluated in vivo by Peters' standard test in mice infected with Plasmodium berghei. The hybrid compound was also assessed for in vivo toxicity. Among all the compounds studied, a DHA-EB hybrid showed an appropriate inhibition percentage (53%) was at a very low dose (0.65 nM). The highest in vivo antimalarial activity until the 9th day was related to DHA-EB in a low dose (0.5 mg/kg). Also, the most survival rate was observed in the test group of hybrid compound at a dose of 1.5 mg/kg for 22 days. No external changes were identified in the toxicity assay. The weight of internal organs of treated animals and that of controls indicated nontoxicity of DHA-EB even after 60 days of consumption. In vitro and in vivo studies substantiated that DHA-EB hybrid has the potential for developing as a safe antimalarial drug.

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.

Enhancement of Anticancer Potential of Artemisinin Derivatives through N-glycosylation

Cancer cells have significantly higher intracellular free-metal ions levels than normal cells, and it is well known that artemisinin (ART) molecules or its derivatives sensitize cancer cells when its endoperoxide moiety combines with metal ions, resulting in the production of reactive oxygen species, lysosomal degradation of ferritin, or regulation of system Gpx4 leading to apoptosis, ferroptosis or cuproptosis. Artemisinin derivatives (ADs) are reported to interfere more efficiently with metal-regulatory-proteins (MRPs) controlling iron/copper homeostasis by interacting with cytoplasmic unbound metal ions and thereby promoting the association of MRP to mRNA molecules carrying the respective sequences. However, the simple artemisinin analogues are required to be administered in higher doses with repeated administration due to low solubility and smaller plasma half-lives. To overcome these problems, amino ARTs were introduced which are found to be more stable, and later on, a series of ARTs derivatives containing sugar moiety was developed in search of analogues having good water solubility and high pharmacological activity. This review focuses on the preparation of N-glycosylated amino-ART analogues with their application against cancer. The intrinsic capability of glycosylated ART compounds is to give sugar-- containing substrates, which can bind with lectin galectin-8 receptors on the cancer cells making these compounds more specific in targeting cancer. Various AD mechanism of action against cancer is also explored with clinical trials to facilitate the synthesis of newer derivatives. In the future, the latest nano-techniques can be used to create formulations of such compounds to make them more target-specific in cancer.

Artemisinin protects dopaminergic neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity in a mouse model of Parkinson's disease

Artemisinin is an antimalarial drug that has been used for almost half a century. However, the anti-Parkinson's disease (PD) effects of artemisinin with respect to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced oxidative stress have not yet been investigated while focusing on NF-E2-related factor 2 (Nrf2) signaling. Thus, we sought to assess the behavioral and oxidative mechanistic effects of artemisinin on MPTP-induced toxicity via the Nrf2 signaling pathway. We explored this through immunohistochemical assays, ELISA, in differentiated PC12 cells treated with siRNA, and with a PD mouse model. Artemisinin increased Nrf2 DNA-binding activity and HO-1 and NQO1 expression. Artemisinin treatment protected cells against MPP+ -induced neuronal death signaling, including NADH dehydrogenase activity, reactive oxygen species, mitochondrial membrane potential, and cleaved caspase-3. Moreover, it protected cells against MPTP-induced behavioral impairments and significantly reduced dopaminergic neuronal loss. Additionally, Nrf2 pre-inhibition using ML385 neutralized the inhibitory effects of artemisinin on dopaminergic neuronal damage and behavioral impairments induced by MPTP. Our results suggest that artemisinin inhibits MPTP-induced behavioral and neurotoxic effects in mice. This provides a foundation for further research to evaluate artemisinin as a potential therapeutic agent for PD.

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).

Quinolines and isoquinolines as HIV-1 inhibitors: Chemical structures, action targets, and biological activities

Human immunodeficiency virus type 1 (HIV-1), a lentivirus that causes acquired immunodeficiency syndrome (AIDS), poses a serious threat to global public health. Since the advent of the first drug zidovudine, a number of anti-HIV agents acting on different targets have been approved to combat HIV/AIDS. Among the abundant heterocyclic families, quinoline and isoquinoline moieties are recognized as promising scaffolds for HIV inhibition. This review intends to highlight the advances in diverse chemical structures and abundant biological activity of quinolines and isoquinolines as anti-HIV agents acting on different targets, which aims to provide useful references and inspirations to design and develop novel HIV inhibitors for medicinal chemists.

Cerebral Malaria and Neuronal Implications of Plasmodium Falciparum Infection: From Mechanisms to Advanced Models

Reorganization of host red blood cells by the malaria parasite Plasmodium falciparum enables their sequestration via attachment to the microvasculature. This artificially increases the dwelling time of the infected red blood cells within inner organs such as the brain, which can lead to cerebral malaria. Cerebral malaria is the deadliest complication patients infected with P. falciparum can experience and still remains a major public health concern despite effective antimalarial therapies. Here, the current understanding of the effect of P. falciparum cytoadherence and their secreted proteins on structural features of the human blood-brain barrier and their involvement in the pathogenesis of cerebral malaria are highlighted. Advanced 2D and 3D in vitro models are further assessed to study this devastating interaction between parasite and host. A better understanding of the molecular mechanisms leading to neuronal and cognitive deficits in cerebral malaria will be pivotal in devising new strategies to treat and prevent blood-brain barrier dysfunction and subsequent neurological damage in patients with cerebral malaria.

Current Progress on Neuroprotection Induced by Artemisia, Ginseng, Astragalus, and Ginkgo Traditional Chinese Medicines for the Therapy of Alzheimer's Disease

Aging is associated with the occurrence of diverse degenerative changes in various tissues and organs and with an increased incidence of neurological disorders, especially neurodegenerative diseases such as Alzheimer's disease (AD). In recent years, the search for effective components derived from medicinal plants in delaying aging and preventing and treating neurodegenerative diseases has been increasing and the number of related publications shows a rising trend. Here, we present a concise, updated review on the preclinical and clinical research progress in the assessment of the therapeutic potential of different traditional Chinese medicines and derived active ingredients and their effect on the signaling pathways involved in AD neuroprotection. Recognized by their multitargeting ability, these natural compounds hold great potential in developing novel drugs for AD.

The antimalarial activity of 1,2,4-trioxolane/trioxane hybrids and dimers: A review

Malaria, a mosquito-borne parasitic infection caused by protozoan parasites belonging to the genus Plasmodium, is a dangerous disease that contributes to millions of hospital visits and hundreds and thousands of deaths across the world, especially in Sub-Saharan Africa. Antimalarial agents are vital for treating malaria and controlling transmission, and 1,2,4-trioxolane/trioxane-containing agents, especially artemisinin and its derivatives, own antimalarial efficacy and low toxicity with unique mechanisms of action. Moreover, artemisinin-based combination therapies were recommended by the World Health Organization as the first-line treatment for uncomplicated malaria infection and have remained as the mainstay of the treatment of malaria, demonstrating that 1,2,4-trioxolane/trioxane derivatives are useful prototypes for the control and eradication of malaria. However, malaria parasites have already developed resistance to almost all of the currently available antimalarial agents, creating an urgent need for the search of novel pharmaceutical interventions for malaria. The purpose of this review article is to provide an emphasis on the current scenario (January 2012 to January 2022) of 1,2,4-trioxolane/trioxane hybrids and dimers with potential antimalarial activity and the structure-activity relationships are also discussed to facilitate further rational design of more effective candidates.

Predicting new potential antimalarial compounds by using Zagreb topological indices

Molecular topology allows describing molecular structures following a two-dimensional approach by taking into account how the atoms are arranged internally through a connection matrix between the atoms that are part of a structure. Various molecular indices (unique for each molecule) can be determined, such as Zagreb, Balaban, and topological indices. These indices have been correlated with physical chemistry properties such as molecular weight, boiling point, and electron density. Furthermore, their relationship with a specific biological activity has been found in other reports. Therefore, its knowledge and interpretation could be critical in the rational design of new compounds, saving time and money in their development process. In this research, the molecular graph of antimalarials already in the pharmaceutical market, such as chloroquine, primaquine, quinine, and artemisinin, was calculated and used to compute the Zagreb indices; a relationship between these indices and the antimalarial activities was found. According to the results reported in this work, the smaller the Zagreb indices, the higher the antimalarial activity. This relationship works very well for other compounds series. Therefore, it seems to be a fundamental structural requirement for this activity. Three triazole-modified structures are proposed as possible potential antimalarials based on this hypothesis. Finally, this work shows that the Zagreb indices could be a cornerstone in designing and synthesizing new antimalarial compounds, albeit they must be proved experimentally.

Biotransformation of artemisinin to a novel derivative via ring rearrangement by Aspergillus niger

Abstract

Artemisinin is a component part of current frontline medicines for the treatment of malaria. The aim of this study is to make analogues of artemisinin using microbial transformation and evaluate their in vitro antimalarial activity. A panel of microorganisms were screened for biotransformation of artemisinin (1). The biotransformation products were extracted, purified and isolated using silica gel column chromatography and semi-preparative HPLC. Spectroscopic methods including LC-HRMS, GC–MS, FT-IR, 1D and 2D NMR were used to elucidate the structure of the artemisinin metabolites.¹H NMR spectroscopy was further used to study the time-course biotransformation. The antiplasmodial activity (IC₅₀) of the biotransformation products of 1 against intraerythrocytic cultures of Plasmodium falciparum were determined using bioluminescence assays. A filamentous fungus Aspergillus niger CICC 2487 was found to possess the best efficiency to convert artemisinin (1) to a novel derivative, 4-methoxy-9,10-dimethyloctahydrofuro-(3,2-i)-isochromen-11(4H)-one (2) via ring rearrangement and further degradation, along with three known derivatives, compound (3), deoxyartemisinin (4) and 3-hydroxy-deoxyartemisinin (5). Kinetic study of the biotransformation of artemisinin indicated the formation of artemisinin G as a key intermediate which could be hydrolyzed and methylated to form the new compound 2. Our study shows that the anti-plasmodial potency of compounds 2, 3, 4 and 5 were ablated compared to 1, which attributed to the loss of the unique peroxide bridge in artemisinin (1). This is the first report of microbial degradation and ring rearrangement of artemisinin with subsequent hydrolysis and methoxylation by A.niger.

Key points

• Aspergillus niger CICC 2487 was found to be efficient for biotransformation of artemisinin

• A novel and unusual artemisinin derivative was isolated and elucidated

• The peroxide bridge in artemisinin is crucial for its high antimalarial potency

• The pathway of biotransformation involves the formation of artemisinin G as a key intermediate

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-022-11888-0.

Artemisinin-Type Drugs in Tumor Cell Death: Mechanisms, Combination Treatment with Biologics and Nanoparticle Delivery

Artemisinin, the most famous anti-malaria drug initially extracted from Artemisia annua L., also exhibits anti-tumor properties in vivo and in vitro. To improve its solubility and bioavailability, multiple derivatives have been synthesized. However, to reveal the anti-tumor mechanism and improve the efficacy of these artemisinin-type drugs, studies have been conducted in recent years. In this review, we first provide an overview of the effect of artemisinin-type drugs on the regulated cell death pathways, which may uncover novel therapeutic approaches. Then, to overcome the shortcomings of artemisinin-type drugs, we summarize the recent advances in two different therapeutic approaches, namely the combination therapy with biologics influencing regulated cell death, and the use of nanocarriers as drug delivery systems. For the former approach, we discuss the superiority of combination treatments compared to monotherapy in tumor cells based on their effects on regulated cell death. For the latter approach, we give a systematic overview of nanocarrier design principles used to deliver artemisinin-type drugs, including inorganic-based nanoparticles, liposomes, micelles, polymer-based nanoparticles, carbon-based nanoparticles, nanostructured lipid carriers and niosomes. Both approaches have yielded promising findings in vitro and in vivo, providing a strong scientific basis for further study and upcoming clinical trials.

Antiplasmodial activity and cytotoxicity of plant extracts from the Asteraceae and Rubiaceae families

The increasing resistance of parasites to antimalarial drugs and the limited number of effective drugs are the greatest challenges in the treatment of malaria. It is necessary to search for an alternative medicine for use as a new, more effective antimalarial drug. Therefore, this study aimed to evaluate the in vitro antimalarial activity and cytotoxicity of extracts from plants belonging to the Asteraceae and Rubiaceae families. The phytoconstituents of one hundred ten ethanolic and aqueous extracts from different parts of twenty-three plant species were analyzed. Evaluation of their antimalarial activities against the chloroquine (CQ)-resistant Plasmodium falciparum (K1) strain was carried out using the lactate dehydrogenase (pLDH) assay, and their cytotoxicity in Vero cells was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric method. A total of 40.91% of the extracts were active antimalarial agents. Three extracts (2.73%) exhibited high antiplasmodial activity (IC50 < 10 μg/ml), twenty-four extracts (21.82%) were moderately active with IC50 values ranging from 10-50 μg/ml, and eighteen extracts (16.36%) were mildly active with IC50 values ranging from 50-100 μg/ml. The ethanolic leaf extract of Mussaenda erythrophylla (Dona Trining; Rubiaceae) exhibited the highest activity against P. falciparum, with an IC50 value of 3.73 μg/ml and a selectivity index (SI) of 30.74, followed by the ethanolic leaf extract of Mussaenda philippica Dona Luz x M. flava (Dona Marmalade; Rubiaceae) and the ethanolic leaf extract of Blumea balsamifera (Camphor Tree; Asteraceae), with IC50 values of 5.94 and 9.66 μg/ml and SI values of 25.36 and >20.70, respectively. GC-MS analysis of these three plant species revealed the presence of various compounds, such as squalene, oleic acid amide, β-sitosterol, quinic acid, phytol, oleamide, α-amyrin, sakuranin, quercetin and pillion. In conclusion, the ethanolic leaf extract of M. erythrophylla, the leaf extract of M. philippica Dona Luz x M. flava and the leaf extract of B. balsamifera had strong antimalarial properties with minimal toxicity, indicating that compounds from these plant species have the potential to be developed into new antiplasmodial agents.

Targeting Reactive Oxygen Species Capacity of Tumor Cells with Repurposed Drug as an Anticancer Therapy

Accumulating evidence shows that elevated levels of reactive oxygen species (ROS) are associated with cancer initiation, growth, and response to therapies. As concentrations increase, ROS influence cancer development in a paradoxical way, either triggering tumorigenesis and supporting the proliferation of cancer cells at moderate levels of ROS or causing cancer cell death at high levels of ROS. Thus, ROS can be considered an attractive target for therapy of cancer and two apparently contradictory but virtually complementary therapeutic strategies for the regulation of ROS to treat cancer. Despite tremendous resources being invested in prevention and treatment for cancer, cancer remains a leading cause of human deaths and brings a heavy burden to humans worldwide. Chemotherapy remains the key treatment for cancer therapy, but it produces harmful side effects. Meanwhile, the process of de novo development of new anticancer drugs generally needs increasing cost, long development cycle, and high risk of failure. The use of ROS-based repurposed drugs may be one of the promising ways to overcome current cancer treatment challenges. In this review, we briefly introduce the source and regulation of ROS and then focus on the status of repurposed drugs based on ROS regulation for cancer therapy and propose the challenges and direction of ROS-mediated cancer treatment.

Transdermal delivery of artemisinins for treatment of pre-clinical cerebral malaria

Transdermal drug delivery avoids complications related to oral or parenteral delivery - the need for sterility, contamination, gastrointestinal side effects, patient unconsciousness or nausea and compliance. For malaria treatment, we demonstrate successful novel transdermal delivery of artemisone (ART) and artesunate. The incorporation of ART into a microemulsion (ME) overcomes the limitations of the lipophilic drug and provides high transcutaneous bioavailability. ART delivery to the blood (above 500 ng/ml) was proved by examining the sera from treated mice, using a bioassay in cultured Plasmodium falciparum. Skin spraying of ART-ME eliminated P. berghei ANKA in an infected mouse model of cerebral malaria (CM) and prevented CM, even after a late treatment with a relatively small amount of ART (13.3 mg/kg). For comparison, the artesunate (the most used commercial artemisinin) formulation was prepared as ART. However, ART-ME was about three times more efficient than artesunate-ME. The solubility and stability of ART in the ME, taken together with the successful transdermal delivery leading to animal recovery, suggest this formulation as a potential candidate for transdermal treatment of malaria.

Advancement of chimeric hybrid drugs to cure malaria infection: An overview with special emphasis on endoperoxide pharmacophores

Emergence and spread of Plasmodium falciparum resistant to artemisinin-based combination therapy has led to a situation of haste in the scientific and pharmaceutical communities. Sincere efforts are redirected towards finding alternative chemotherapeutic agents that are capable of combating multidrug-resistant parasite strains. Extensive research yielded the concept of "Chimeric Bitherapy (CB)" which involves the linking of two molecules with individual pharmacological activity and exhibit dual mode of action into a single hybrid molecule. Current research in this field seems to endorse hybrid molecules as the next-generation antimalarial drugs and are more effective compared to the multi-component drugs because of the lower occurrence of drug-drug adverse effects. This review is an attempt to congregate complete survey on endoperoxide based hybrid antiplasmodial molecules that will give glimpse on the future directions for successful development and discovery of useful antimalarial hybrid drugs.