Current scenario of artemisinin and its analogues for antimalarial activity

Novel saturated 1,2,4-trioxanes and their antimalarial activity against multidrug resistant Plasmodium yoelii nigeriensis in Swiss mice model via oral route

Novel saturated 6-(4'-aryloxy phenyl) vinyl 1,2,4-trioxanes 12a(1-3)-12d(1-3) and 13a(1-3)-13d(1-3) have been designed and synthesized, in one single step from diimide reduction of 11a(1-3)-11d(1-3). All the newly synthesized trioxanes were evaluated for their antimalarial activity against multi-drug resistant Plasmodium yoelii nigeriensis via oral route. Cyclopentane-based trioxanes 12b1, 12c1 and 12d1, provided 100 % protection to the infected mice at 24 mg/kg × 4 days. The most active compound of the series, trioxane 12b1, provided 100 % protection even at 12 mg/kg × 4 days and 60 % protection at 6 mg/kg × 4 days. The currently used drug, β-arteether provides only 20 % protection at 24 mg/kg × 4 days.

Exploring the modulatory influence on the antimalarial activity of amodiaquine using scaffold hybridisation with ferrocene integration

Amodiaquine (AQ) is a potent antimalarial drug used in combination with artesunate as part of artemisinin-based combination therapies (ACTs) for malarial treatment. Due to the rising emergence of resistant malaria parasites, some of which have been reported for ACT, the usefulness of AQ as an efficacious therapeutic drug is threatened. Employing the organometallic hybridisation approach, which has been shown to restore the antimalarial activity of chloroquine in the form of an organometallic hybrid clinical candidate ferroquine (FQ), the present study utilises this strategy to modulate the biological performance of AQ by incorporating ferrocene. Presently, we have conceptualised ferrocenyl AQ derivatives and have developed facile, practical routes for their synthesis. A tailored library of AQ derivatives was assembled and their antimalarial activity evaluated against chemosensitive (NF54) and multidrug-resistant (K1) strains of the malaria parasite, Plasmodium falciparum. The compounds generally showed enhanced or comparable activities to those of the reference clinical drugs chloroquine and AQ, against both strains, with higher selectivity for the sensitive phenotype, mostly in the double-digit nanomolar IC50 range. Moreover, representative compounds from this series show the potential to block malaria transmission by inhibiting the growth of stage II/III and V gametocytes in vitro. Preliminary mechanistic insights also revealed hemozoin inhibition as a potential mode of action.

Novel ether derivatives of 11-azaartemisinins with high order antimalarial activity against multidrug-resistant Plasmodium yoelii in Swiss mice

This study investigates cutting-edge synthetic chemistry approaches for designing and producing innovative antimalarial drugs with improved efficacy and fewer adverse effects. Novel amino (-NH2) and hydroxy (-OH) functionalized 11-azaartemisinins 9, 12, and 14 were synthesized along with their derivatives 11a, 13a-e, and 15a-b through ART and were tested for their AMA (antimalarial activity) against Plasmodium yoelii via intramuscular (i.m.) and oral routes in Swiss mice. Ether derivative 13c was the most active compound by i.m. route, it has shown 100 % protection at the dose of 12 mg/kg × 4 days and showed 100 % clearance of parasitaemia on day 4 at dose of 6 mg/kg. Amine 11a, ether derivatives 13d, 13e and ether 15a also showed promising antimalarial activity. β-Arteether gave 100 % protection at the dose of 48 mg/kg × 4 days and 20 % protection at 24 mg/kg × 4 days dose by oral route, while it showed 100 % protection at 6 mg/kg × 4 days and no protection at 3 mg/kg × 4 days by i.m. route.

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.

Novel amino- and hydroxy-functionalized 1,2,4-trioxanes and their antimalarial activity against multidrug-resistant Plasmodium yoelii nigeriensis in Swiss mice via intramuscular and oral route

Following the economic and social state of humanity, Malaria is categorized as one of the life-threatening illness epidemics in under developed countries. For the eradication of the same, 1,2,4-trioxanes 17a1-a2, 17b1-b2, 17c1-c2 15a-c, 18 and 19 have been synthesized continuing the creation of a novel series. Additionally, these novel compounds were tested for their effectiveness against the multidrug-resistant Plasmodium yoelii nigeriensis in mice model using both oral and intramuscular (im) administration routes. The two most potent compounds of the series, 17a1 and 17a2, demonstrated 100 % protection at 48 mg/kg x 4 days via oral route, which is twice as potent as artemisinin. In this model artemisinin provided 100 % protection at a dose of 48 mg/kg × 4 days and 80 % protection at 24 mg/kg × 4 days via im route.

New clinical application prospects of artemisinin and its derivatives: a scoping review

BACKGROUND

Recent research has suggested that artemisinin and its derivatives may have therapeutic effects on parasites, viruses, tumors, inflammation and skin diseases. This study aimed to review clinical research on artemisinin and its derivatives except anti-malaria and explore possible priority areas for future development.

METHODS

Relevant articles in English and Chinese published before 28 October 2021 were reviewed. All articles were retrieved and obtained from databases including WanFang, PubMed/MEDLINE, the Cochrane Library, China National Knowledge International, Embase, OpenGrey, the Grey Literature Report, Grey Horizon, and ClinicalTrials.gov. Studies were selected for final inclusion based on predefined criteria. Information was then extracted and analyzed by region, disease, outcome, and time to identify relevant knowledge gaps.

RESULTS

Seventy-seven studies on anti-parasitic (35), anti-tumor (16), anti-inflammatory (12), anti-viral (8), and dermatological treatments (7) focused on the safety and efficacy of artemisinin and its derivatives. The anti-parasitic clinical research developed rapidly, with a large number of trials, rapid clinical progress, and multiple research topics. In contrast, anti-viral research was limited and mainly stayed in phase I clinical trials (37.50%). Most of the studies were conducted in Asia (60%), followed by Africa (27%), Europe (8%), and the Americas (5%). Anti-parasite and anti-inflammatory research were mainly distributed in less developed continents such as Asia and Africa, while cutting-edge research such as anti-tumor has attracted more attention in Europe and the United States. At the safety level, 58 articles mentioned the adverse reactions of artemisinin and its derivatives, with only one study showing a Grade 3 adverse event, while the other studies did not show any related adverse reactions or required discontinuation. Most studies have discovered therapeutic effects of artemisinin or its derivatives on anti-parasitic (27), anti-tumor (9), anti-inflammatory (9) and dermatological treatment (6). However, the efficacy of artemisinin-based combination therapies (ACTs) for parasitic diseases (non-malaria) is still controversial.

CONCLUSIONS

Recent clinical studies suggest that artemisinin and its derivatives may be safe and effective candidates for anti-tumor, anti-parasitic, anti-inflammatory and dermatological drugs. More phase II/III clinical trials of artemisinin and its derivatives on antiviral effects are needed.

Peroxide-Simulating and GSH-Depleting Nanozyme for Enhanced Chemodynamic/Photodynamic Therapy via Induction of Multisource ROS

Reactive oxygen species (ROS) generation, using photodynamic therapy (PDT) and chemodynamic therapy (CDT), is a promising strategy for cancer treatment. However, the production of ROS in tumor cells is often limited by hypoxia, insufficient substrates, and high level of ROS scavengers in a tumor microenvironment, which seriously affects the efficacy of ROS-related tumor therapies. Herein, we report a lipid-supported manganese oxide nanozyme, MLP@DHA&Ce6, by decorating a MnO2 nano-shell on the liposome loaded with dihydroartemisinin (DHA) and photosensitizer Ce6 for generating multisource ROS to enhance cancer therapy. MLP@DHA&Ce6 can be accumulated in tumors and can release active components, Mn2+ ions, and O2. The conjugate generates ROS via nanozyme-catalyzed CDT using DHA as a substrate, PDT through Ce6, and the Fenton reaction catalyzed by Mn2+ ions. The production of O2 from MnO2 enhanced Ce6-mediated PDT under near-infrared light irradiation. Meanwhile, MLP@DHA&Ce6 showed prominent glutathione depletion, which allowed ROS to retain high activity in tumor cells. In addition, the release of Mn2+ ions and DHA in tumor cells induced ferroptosis. This multisource ROS generation and ferroptosis effect of MLP@DHA&Ce6 led to enhanced therapeutic effects in vivo.

Novel Bis-Artemisinin-Phloroglucinol hybrid molecules with dual anticancer and immunomodulatory Activities: Synthesis and evaluation

Bis-(10-deoxydihydroartemisinin)-phloroglucinol (9), has been synthesized in a one-step reaction and has demonstrated strong inhibition to cancer cell proliferation and immunosuppressive activity. The structure modification of the compound reduced its cytotoxicity, and among the analogs, bis-(10-deoxydihydroartemisinin)-phloroglucinol phenyl decanoate (16) showed significant reduction of ear swelling in a mouse model for DNFB-induced delayed-type hypersensitivity without observable toxicity in a dose-dependent manner.

Drug Repurposing to Circumvent Immune Checkpoint Inhibitor Resistance in Cancer Immunotherapy

Immune checkpoint inhibitors (ICI) have achieved unprecedented clinical success in cancer treatment. However, drug resistance to ICI therapy is a major hurdle that prevents cancer patients from responding to the treatment or having durable disease control. Drug repurposing refers to the application of clinically approved drugs, with characterized pharmacological properties and known adverse effect profiles, to new indications. It has also emerged as a promising strategy to overcome drug resistance. In this review, we summarized the latest research about drug repurposing to overcome ICI resistance. Repurposed drugs work by either exerting immunostimulatory activities or abolishing the immunosuppressive tumor microenvironment (TME). Compared to the de novo drug design strategy, they provide novel and affordable treatment options to enhance cancer immunotherapy that can be readily evaluated in the clinic. Biomarkers are exploited to identify the right patient population to benefit from the repurposed drugs and drug combinations. Phenotypic screening of chemical libraries has been conducted to search for T-cell-modifying drugs. Genomics and integrated bioinformatics analysis, artificial intelligence, machine and deep learning approaches are employed to identify novel modulators of the immunosuppressive TME.

Acidity-Triggered Charge-Convertible Conjugated Polymer for Dihydroartemisinin Delivery and Tumor-Specific Chemo-Photothermal Therapy

Since the nonspecificity and nonselectivity of traditional treatment models lead to the difficulty of cancer treatment, nanobased strategies are needed to fill in the gaps of current approaches. Herein, a tumor microenvironment (TME)-responsive chemo-photothermal treatment model was developed based on dihydroartemisinin (DHA)-loaded conjugated polymers (DHA@PLGA-PANI). The synthesized DHA@PLGA-PANI exhibited enhanced photothermal properties under mild-acidic conditions and thus triggered local heat at the tumor site. Meanwhile, these iron-doped conjugated polymers of PLGA-PANI were used as the source of Fe, and benefiting from the Fe-dependent cytotoxicity of DHA, the burst of free radicals could be generated in tumors. Therefore, the combination of TME-responsive chemo-photothermal therapy could achieve effective tumor efficacy.

Dihydroartemisinin-ursodeoxycholic acid conjugate is a potential treatment agent for inflammatory bowel disease

BACKGROUND

A novel artemisinin derivative, dihydroartemisinin-ursodeoxycholic acid conjugate (4), was found to exhibit strong immunosuppressive activity. Various methods were used to evaluate the immunosuppressive activity and mechanism of action of the compound to explore its potential applications.

METHODS

T cell proliferation, mixed lymphocyte reaction (MLR), and Th1/Th17 differentiation assays were used to evaluate the immunosuppressive activity of the compound. Differentially expressed genes from RNA sequencing were analysed with Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, while enriched signalling pathways were further validated by western blotting (WB). In vivo efficacy was validated with delayed-type hypersensitivity (DTH) mouse models and dextran sodium sulphate (DSS)-induced inflammatory bowel disease (IBD) mouse model.

RESULTS

Compound 4 inhibited concanavalin A -induced mouse splenic T cell proliferation (IC₅₀ = 15 nM) and anti-CD3/CD28-induced human primary T cell proliferation (IC₅₀ = 30 nM) while also reducing the secretion of hIFN-γ. Compound 4 exhibited similar inhibitory activity in MLR assay. Compound 4 dose-dependently inhibited human Th1/Th17 differentiation. The KEGG pathway enrichment analysis indicated that the genes related to T cell activation signalling pathways PI3K-AKT, MAPK, and NF-κB were significantly enriched. WB confirmed that compound 4 inhibited the AKT/MAPK and NF-κB signalling pathways. Compound 4 dose-dependently inhibited ear and foot pad swelling in DTH mouse models. In the DSS-induced IBD mouse model, compound 4 significantly decreased the disease activity index and colon density, and inhibited splenomegaly of the mice.

CONCLUSION

The in vitro and in vivo results indicated that compound 4 has the potential to be developed into an anti-IBD drug.

A comprehensive overview of Artemisinin and its derivatives as anticancer agents

Artemisinin is the crucial ingredient of artemisia annua, a traditional Chinese medicine used for the therapy of malaria in China for hundreds of years. In recent years, the anticancer properties of artemisinin and its derivatives have also been reported. This review has summarized the research and development of artemisinin and its derivatives as anticancer agents, which included both natural and synthetic monomers as well as their dimers. In addition, it highlights the antitumor effects of artemisinin and its derivatives after site-modification or after transformation to a nano-delivery system. Moreover, we have further explored their potential mechanisms of action and also discussed the clinical trials of ARTs used to treat cancer, which will facilitate in further development of novel anticancer drugs based on the scaffold of artemisinin.

Hitting drug-resistant malaria infection with triazole-linked flavonoid-chloroquine hybrid compounds

Background: Malaria represents the major parasitic disease in tropical regions, and the development of new potent drugs is of pivotal importance. In this study, a series of hybrid molecules were designed by linking the 7-chloroquinoline core of chloroquine to different fluorinated flavonoid-related scaffolds. Materials & methods: Compounds were prepared by exploiting the click chemistry approach, allowing the introduction of a 1,2,3-triazole, a privileged structural motif in antiparasitic dug discovery. Results: Compounds 1b and 1c were the most interesting and were endowed with the highest in vitro activity, mainly against a resistant Plasmodium falciparum strain. They also inhibited hemozoin formation, and 1c was more effective than chloroquine against stage V gametocytes. Conclusion: The homoisoflavone core is a new, promising antimalarial scaffold that deserves further investigation.

Enhanced and sustained transdermal delivery of primaquine from polymeric thermoresponsive hydrogels in combination with Dermarollers®

Primaquine (PMQ) is an effective antimalaria drug with several limitations. We report the combinatorial approach of thermoresponsive hydrogels and Dermarollers® for transdermal delivery of PMQ to overcome these limitations. The hydrogels were prepared using Pluronic F127 (PF127) and F68 (PF68). Specifically, HPMC was added into the formulation to improve the bioadhesive properties. Numerous formulations were prepared, showing that formulation comprising 15 % PF127, 3 % PF68 and 0.4 % HPMC with 1 % PMQ was selected as the optimum formulation. The formulation showed the gelation temperature around 35 °C with bioadhesive strength of 26.43 ± 2.31 dyne.cm2. Importantly, the pH of the formulation was suitable for skin application with the percentage of PMQ recovery of 99.57 ± 3.23 %. Moreover, the hydrogels exhibited free-flow liquid at storage and room temperature and high viscosities in the skin temperature. In vitro release experiments showed that the release of PMQ was sustained for 24 h. Evaluated in extensive ex vivo studies, the treatment with Dermarollers® improved the skin permeation and retention of PMQ for 3 days. In combination with Dermarollers®, the ex vivo permeation of PMQ was sustained and the localization of PMQ in the skin was improved over 72 h.

Sesquiterpene lactones from Artemisia vulgaris L. as potential NO inhibitors in LPS-induced RAW264.7 macrophage cells

Twelve new guaianolide sesquiterpene lactones (1–12), along with ten known analogs (13–22) were isolated from an EtOH extract of the dried aerial parts of Artemisia vulgaris L. The new structures were elucidated via abundant spectroscopic data analyses (HRESIMS, IR, 1D, and 2D NMR), and the absolute configurations of these compounds were determined by X-ray crystallography and ECD calculations. The compounds (1−22) were identified as guaiane-type sesquiterpenes with characteristic α-methylene-γ-lactone and α,β-unsaturated carbonyl moieties. All compounds were tested for their inhibitory activity against NO production in lipopolysaccharide-stimulated RAW264.7 macrophages. The isolated sesquiterpenoids dose-dependently exhibited an NO production inhibitory activity by inhibiting the expression of inducible NO oxidase (iNOS) and cyclooxygenase-2 (COX-2) with IC₅₀ values ranging from 1.0 to 3.6 μM. The inhibitory effect on the NO production of the compounds (1–4 and 6–22) is better than that of the positive control (dexamethasone). The different substitutions of compounds on C-8 influence anti-inflammatory effects, as evidenced by the in silico analysis of related binding interactions of new compounds (1–12) with iNOS.

Anti-malarial effect of a combination of risedronate and azithromycin against Plasmodium yoelii nigeriensis infection in Swiss mice

Combination therapy is used to retard the selection of malaria parasite strains resistant to individual components of a combination of drugs. This approach has proved to be a success in the combination of sulphadoxine and pyrimethamine, which targets two different steps in the folate pathway of malaria parasites. However, after the success of this therapeutic combination, the efficacy of other combinations of drugs that target different enzymes in a particular metabolic pathway has, apparently, not been reported. In the current study, the antimalarial effect of a combination of risedronate (RIS), which is known for its anti-osteoporosis activity, and azithromycin (AZT) was investigated. Peter's suppression test was carried out on mice infected with 1 × 10⁷P. yoelii infected erythrocytes. Drug efficacy was analyzed by comparing the percent reduction in parasitaemia on day 4 post-infection. RIS was observed to be a blood schizonticidal agent against P. yoelii infection which showed ED₅₀ 7.0 (4.04-12.13) mg/kg/day x 4. Normalized isobologram showed additive action between RIS 1 mg/kg/day x 4 and AZT 10 mg/kg/day x 4, and antagonistic action for the rest of the combinations (RIS 1 + AZT 20, RIS 1 + AZT 40, RIS 5 + AZT 10, RIS 5 + AZT 20, RIS 5 + AZT 40, RIS 10 + AZT 10, RIS 10 + AZT 20 and RIS 10 + AZT 40 mg/kg/day x 4). Furthermore, a combination of RIS with AZT showed inferior efficacy as compared to AZT treatment alone. This antagonistic interaction may be due to the high accumulation of AZT in WBCs, which will reduce its serum bio-availability, whereas RIS has anti-parasitic activity by increasing WBCs.

Plant-based engineering for production of high-valued natural products

Covering: up to March 2022Plants are a unique source of complex specialized metabolites, many of which play significant roles in human society. In many cases, however, the availability of these metabolites from naturally occurring sources fails to meet current demands. Thus, there is much interest in expanding the production capacity of target plant molecules. Traditionally, plant breeding, chemical synthesis, and microbial fermentation are considered the primary routes towards large scale production of natural products. Here, we explore the advances, challenges, and future of plant engineering as a complementary path. Although plants are an integral part of our food and agricultural systems and sustain an extensive array of chemical constituents, their complex genetics and physiology have prevented the optimal exploitation of plants as a production chassis. We highlight emerging engineering tools and scientific advances developed in recent years that have improved the prospects of using plants as a sustainable and scalable production platform. We also discuss technological limitations and overall economic outlook of plant-based production of natural products.

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.

Mechanistic Evaluation of the Stability of Arylvinyl-1,2,4-trioxanes under Acidic Conditions for Their Oral Administration as an Antimalarial Drug

A mechanistic approach to understand the course of metabolism for synthetic 1,2,4-trioxanes, potent antimalarial compounds, to evaluate their bioavailability for antimalarial action has been studied in the present work. It is an important parameter to study the course of metabolism of a drug candidate molecule when administered via oral route during its journey from oral intake to its target site. From the pharmacokinetics point of view, it determines the bioavailability of an active drug or a prodrug at the target point. In this work, synthetic arylvinyl-1,2,4-trioxanes 1a-u have been evaluated under various acidic conditions to mimic the milieu of the stomach (pH between 1.5 and 3.5) through which they have to pass when administered orally. The effect of acid on trioxanes led to their degradation into corresponding ketones and glyoxal. Under such acidic conditions glyoxal polymerized to form a nonisolable condensate product. The study indicates that the actual bioavailability of the drug is far less than the administered dose.

A Novel Antimalarial Metabolite in Erythrocyte From the Hydroxylation of Dihydroartemisinin by Cunninghamella elegans

Dihydroartemisinin (DHA) is a sesquiterpene endoperoxide with prominent antimalarial efficacy, which was discovered by Professor Youyou Tu through the reduction of artemisinin in the 1970s. It is always a challenging work for scientists to investigate the metabolites of DHA in the red blood cells due to the complicated matrix background. As a bottleneck, the investigation of metabolites, especially exploring the pharmacodynamic material in the red blood cell, is necessary and significant for metabolism research of antimalarial agent. Recently, microbial transformation provides a green and economical means for mimicking mammal metabolism and synthesis active metabolites, based on which is one efficient route for drug discovery. In this study, a strain from Cunninghamella was employed as an efficient tool to explore active metabolites of DHA in erythrocyte. Microbial transformation products of DHA by Cunninghamella elegans CICC 40250 were detected and analyzed by ultra-performance liquid chromatography (UPLC)-electrospray ionization (ESI)-quadrupole time-of-flight (Q-TOF)-mass spectrometry (MS^E), and the main products were isolated and identified. The antimalarial activity of the isolated products was also screened in vitro. Totally, nine products were discovered through UPLC-ESI-QTOF-MS^E, and three main products with novel chemical structures were isolated for the first time, which were also detected in red blood cells as the metabolites of DHA. After evaluation, 7β-hydroxydihydroartemisinin (M1) exhibited a good antimalarial activity with an IC₅₀ value of 133 nM against Plasmodium falciparum (Pf.) 3D7. The structure and stereo-configuration of novel compound M1 were validated via X-ray single crystal diffraction. Microbial transformation was firstly employed as the appropriate model for metabolic simulation in erythrocyte of DHA. Three novel metabolites in erythrocyte were obtained for the first time through our microbial model, and one of which was found to show moderate antimalarial activity. This work provided a new research foundation for antimalarial drug discovery.

Flavonoids in Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) is a progressive systemic disease, which changes the function and structure of the kidneys irreversibly over months or years. The final common pathological manifestation of chronic kidney disease is renal fibrosis and is characterized by glomerulosclerosis, tubular atrophy, and interstitial fibrosis. In recent years, numerous studies have reported the therapeutic benefits of natural products against modern diseases. Substantial attention has been focused on the biological role of polyphenols, in particular flavonoids, presenting broadly in plants and diets, referring to thousands of plant compounds with a common basic structure. Evidence-based pharmacological data have shown that flavonoids play an important role in preventing and managing CKD and renal fibrosis. These compounds can prevent renal dysfunction and improve renal function by blocking or suppressing deleterious pathways such as oxidative stress and inflammation. In this review, we summarize the function and beneficial properties of common flavonoids for the treatment of CKD and the relative risk factors of CKD.

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.

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.

The Changing Global Landscape in the Development of Artemisinin-Based Treatments: A Clinical Trial Perspective

Artemisinin and its derivatives (ARTs), due to their potent antimalarial activities, are widely used as frontline antimalarials across the world. Although the large-scale deployment of ARTs has significantly contributed to a substantial decline in malaria deaths, the global malaria burden is still high. New antimalarial treatments need to be developed to manage the growing artemisinin resistance. Understanding the status of ART development is crucial for developing strategies for new alternatives and identifying opportunities to develop ART-based treatments. This study sampled ART clinical trials from the past two decades to gain an overview of the global ART-development landscape. A total of 768 trials were collected to analyze the disease focuses, activity trends, development status, geographic distribution, and combination treatment profiles of ART trials. The findings highlighted the constant focus of ARTs on malaria, the evolving combination research focus, the distinctions between ART development preferences across global regions, the urgent demands for treatments for artemisinin-resistant malaria, and the unavoidable need to consider ART combinations in the development of new antimalarials.

Antimalarial Natural Products

Natural products have made a crucial and unique contribution to human health, and this is especially true in the case of malaria, where the natural products quinine and artemisinin and their derivatives and analogues, have saved millions of lives. The need for new drugs to treat malaria is still urgent, since the most dangerous malaria parasite, Plasmodium falciparum, has become resistant to quinine and most of its derivatives and is becoming resistant to artemisinin and its derivatives. This volume begins with a short history of malaria and follows this with a summary of its biology. It then traces the fascinating history of the discovery of quinine for malaria treatment and then describes quinine's biosynthesis, its mechanism of action, and its clinical use, concluding with a discussion of synthetic antimalarial agents based on quinine's structure. The volume then covers the discovery of artemisinin and its development as the source of the most effective current antimalarial drug, including summaries of its synthesis and biosynthesis, its mechanism of action, and its clinical use and resistance. A short discussion of other clinically used antimalarial natural products leads to a detailed treatment of other natural products with significant antiplasmodial activity, classified by compound type. Although the search for new antimalarial natural products from Nature's combinatorial library is challenging, it is very likely to yield new antimalarial drugs. The chapter thus ends by identifying over ten natural products with development potential as clinical antimalarial agents.

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.

Artemisinin and Derivatives-Based Hybrid Compounds: Promising Therapeutics for the Treatment of Cancer and Malaria

Cancer and malaria are major health conditions around the world despite many strategies and therapeutics available for their treatment. The most used strategy for the treatment of these diseases is the administration of therapeutic drugs, which suffer from several shortcomings. Some of the pharmacological limitations associated with these drugs are multi-drug resistance, drug toxicity, poor biocompatibility and bioavailability, and poor water solubility. The currently ongoing preclinical studies have demonstrated that combination therapy is a potent approach that can overcome some of the aforementioned limitations. Artemisinin and its derivatives have been reported to exhibit potent efficacy as anticancer and antimalarial agents. This review reports hybrid compounds containing artemisinin scaffolds and their derivatives with promising therapeutic effects for the treatment of cancer and malaria.

Study on the structure-activity relationship of dihydroartemisinin derivatives: Discovery, synthesis, and biological evaluation of dihydroartemisinin-bile acid conjugates as potential anticancer agents

A series of dihydroartemisinin derivatives was synthesized, and their anti-proliferation activity against cancer cells was evaluated. Structure-activity relationship studies led to the discovery of dihydroartemisinin-bile acid conjugates that exhibit broad-spectrum anti-proliferation activities. Among them, the dihydroartemisinin-ursodeoxycholic acid conjugate (49) was the most potent, with IC50 values between 0.04 and 0.96 μM when tested to determine its inhibitory properties against 15 various cancer cell lines. In vivo experiments showed that compound 49 effectively suppressed tumor growth in an A549 cell xenograft model at the dosage of 10 mg/kg body weight and in Lewis lung cancer cell transplant model at the dosage of 12 mg/kg body weight.

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.

Artemisinin Cocrystals for Bioavailability Enhancement. Part 2: In Vivo Bioavailability and Physiologically Based Pharmacokinetic Modeling

We report the evaluation and prediction of the pharmacokinetic (PK) performance of artemisinin (ART) cocrystal formulations, that is, 1:1 artemisinin/orcinol (ART-ORC) and 2:1 artemisinin/resorcinol (ART²-RES), using in vivo murine animal and physiologically based pharmacokinetic (PBPK) models. The efficacy of the ART cocrystal formulations along with the parent drug ART was tested in mice infected with Plasmodium berghei. When given at the same dose, the ART cocrystal formulation showed a significant reduction in parasitaemia at day 4 after infection compared to ART alone. PK parameters including C_max (maximum plasma concentration), T_max (time to C_max), and AUC (area under the curve) were obtained by determining drug concentrations in the plasma using liquid chromatography-high-resolution mass spectrometry (LC-HRMS), showing enhanced ART levels after dosage with the cocrystal formulations. The dose-response tests revealed that a significantly lower dose of the ART cocrystals in the formulation was required to achieve a similar therapeutic effect as ART alone. A PBPK model was developed using a PBPK mouse simulator to accurately predict the in vivo behavior of the cocrystal formulations by combining in vitro dissolution profiles with the properties of the parent drug ART. The study illustrated that information from classical in vitro and in vivo experimental investigations of the parent drug of ART formulations can be coupled with PBPK modeling to predict the PK parameters of an ART cocrystal formulation in an efficient manner. Therefore, the proposed modeling strategy could be used to establish in vitro and in vivo correlations for different cocrystals intended to improve dissolution properties and to support clinical candidate selection, contributing to the assessment of cocrystal developability and formulation development.

Novel naphthyl based 1,2,4-trioxanes: Synthesis and in vivo efficacy in the Plasmodium yoelii nigeriensis in Swiss mice

A new series of 1,2,4-trioxanes 9a1-a4, 9b1-b4, 10-13 and 9c1-c4 were synthesized and evaluated against multidrug-resistant Plasmodium yoelii nigeriensis in Swiss mice via oral and intramuscular (i.m.) routes. Adamantane-based trioxane 9b4, the most active compound of the series, provided 100% protection to the infected mice at the dose 48 mg/kg × 4 days and 100% clearance of parasitemia at the dose 24 mg/kg × 4 days via oral route. Adamantane-based trioxane 9b4, is twice active than artemisinin. We have also studied the photooxygenation behaviour of allylic alcohols 6a-b (3-(4-alkoxynaphthyl)-but-2-ene-1-ols) and 6c (3-[4-(tert-butyl-dimethyl-silanyloxy)-naphthalen-1-yl]-but-2-en-1-ol). Being behaving as dienes, they furnished corresponding endoperoxides, while behaving as allylic alcohols, they yielded β-hydroxyhydroperoxides. All the endoperoxides (7a-c) and β-hydroxyhydroperoxides (8a-c) have been separately elaborated to the corresponding 1,2,4-trioxanes, except from endoperoxide 7c. It is worthy to note that TBDMS protected naphthoyl endoperoxide 7c unable to deliver 1,2,4-trioxane, which demonstrated the strength of the O-Si bond is not easy to cleave under acidic condition.

Synthesis of cyclic aza-peroxides (microreview)

A summary of approaches developed for the synthesis of stable cyclic aza-peroxides is presented.

Electrospun Nanofibers of Polycaprolactone/Collagen as a Sustained-Release Drug Delivery System for Artemisinin

The application of artemisinin (ART) in the treatment of malaria has been restricted to a certain degree due to its inherent limitations, such as short half-life, poor solubility, limited bioavailability, and re-crystallization. Electrospun nanofibers loaded with ART provide an excellent solution to these limitations and yield sustained drug release as well as inhibition of drug re-crystallization. In this study, ART-loaded polycaprolactone (PCL)/collagen (Col) nanofibers with different proportions of polymers were prepared. ART-loaded PCL/Col nanofibers were characterized, and further ART anti-crystallization and release behaviors were studied. SEM was used to observe the morphology of PCL/Col nanofibers. X-ray diffraction (XRD) was used to characterize the physical state of ART in ART-loaded PCL/Col nanofibers. Fourier transform infrared spectroscopy (FTIR), water contact angle measurement, weight loss, degree of swelling, and drug release experiments can verify the differences in performance of ART-loaded PCL/Col nanofibers due to different polymer ratios. The release curve was analyzed by kinetics, showing sustained release for up to 48 h, and followed the Fickian release mechanism, which was shown by the diffusion index value obtained from the Korsmeyer-Peppas equation.

Synthesis of novel 1,2,4-trioxanes and antimalarial evaluation against multidrug-resistant Plasmodium yoelii nigeriensis

Malaria epidemics represent one of the life-threatening diseases to low-income lying countries which subsequently affect the economic and social condition of mankind. In continuation in the development of a novel series of 1,2,4-trioxanes 13a1-c1, 13a2-c2, and 13a3-c3 have been prepared and further converted into their hemisuccinate derivatives 14a1-c1, 14a2-c2, and 14a3-c3 respectively. All these new compounds were evaluated for their antimalarial activity against multidrug-resistant Plasmodium yoelii nigeriensis in mice by both oral and intramuscular (im) routes. Hydroxy-functionalized trioxane 13a1 showed 80% protection and its hemisuccinate derivative 14a1 showed 100% protection at a dose of 48 mg/kg × 4 days by both routes, which is twice active than artemisinin by oral route.

Recent pharmacological advances in the repurposing of artemisinin drugs

Artemisinins are a family of sesquiterpene lactones originally derived from the sweet wormwood (Artemisia annua). Beyond their well-characterized role as frontline antimalarial drugs, artemisinins have also received increased attention for other potential pharmaceutical effects, which include antiviral, antiparsitic, antifungal, anti-inflammatory, and anticancer activities. With concerted efforts in further preclinical and clinical studies, artemisinin-based drugs have the potential to be viable treatments for a great variety of human diseases. Here, we provide a comprehensive update on recent reports of pharmacological actions and applications of artemisinins outside of their better-known antimalarial role and highlight their potential therapeutic viability for various diseases.

Network analysis of the effects of long non-coding RNAs in artemisinin treatment of atherosclerosis in APOE-/- mice

Introduction

Atherosclerosis has become a worldwide medical burden. Our previous studies have shown that artemisinin (ART) had the capability to reduce atherosclerosis. Emerging evidence indicates that long non-coding RNAs (lncRNAs) are involved in the development of atherosclerosis. However, whether lncRNAs might participate in the mechanism through which artemisinin mitigates atherosclerosis has not been reported.

Material and methods

Eight-week-old apolipoprotein E deficient (APOE-/-) mice were divided into two groups, one of which was treated with artemisinin. Red oil O staining was used to measure the sizes of the atherosclerotic lesions. We conducted deep sequencing to investigate lncRNA profiles in the aorta tissue in high-fat diet fed APOE knockdown mice with and without artemisinin treatment. CeRNA network, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses were performed through bioinformatics analysis. RT-PCR was used to validate the differentially expressed lncRNAs.

Results

A total of 102 lncRNAs and 4,630 mRNAs were differentially expressed (p < 0.05) between the artemisinin treatment group and atherosclerosis model group. KEGG and GO analyses indicated that the categories metabolic process, specific amino acid degradation and PI3K-Akt signaling pathway are involved in the effects of artemisinin treatment in atherosclerosis (q < 0.05). LncRNA ENSMUST00000099676.4, ENSMUST00000143673.1, ENSMUST00000070085.5 and ENSMUST00000224554 might be engaged in the treatment mechanism through which artemisinin alleviates atherosclerosis.

Conclusions

These findings indicated the possible mechanism and therapeutic role of lncRNAs in artemisinin treatment of atherosclerosis and provided a theoretical basis for the future application of artemisinin in patients with atherosclerosis.

Dihydroartemisinin loaded layered double hydroxide nanocomposites for tumor specific photothermal-chemodynamic therapy

With the inspiration to develop new cancer nanotherapeutics by repurposing old drugs, in the current study, a novel two dimensional nanomedicine namely Mn doped, dihydroartemisinin (DHA) loaded layered double hydroxide (MnMgFe-LDH/DHA) with peroxide self-supplying properties for enhanced photothermal-chemodynamic therapy was proposed. Such nanostructures could be synthesized by a simple coprecipitation method, and the as-prepared MnMgFe-LDH/DHA exhibits excellent photothermal properties with a photothermal conversion efficiency up to 10.7%. Besides, the in situ reaction between the released DHA and Fe2+/Mn2+ produced by the degradation of LDH can lead to a burst of intracellular reactive oxygen species (ROS) by Fenton-like reactions. Furthermore, the in vivo experiments demonstrate that MnMgFe-LDH/DHA exhibits a remarkable chemodynamic/photothermal therapy (CDT/PTT) synergistic effect on tumor treatment with negligible damage to normal tissues. Finally, this research provides a smart strategy to construct a DHA repurposing nanomedicine for tumor specific treatment.

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

Malaria is a life-threatening infectious disease caused by protozoal parasites belonging to the genus Plasmodium. It caused an estimated 405,000 deaths and 228 million malaria cases globally in 2018 as per the World Malaria Report released by World Health Organization (WHO) in 2019. Artemisinin (ART), a "Nobel medicine" and its derivatives have proven potential application in antimalarial drug discovery programs. In this review, antimalarial activity of the most active artemisinin derivatives modified at C-10/C-11/C-16/C-6 positions and synthetic peroxides (endoperoxides, 1,2,4-trioxolanes, 1,2,4-trioxanes, and 1,2,4,5-tetraoxanes) are systematically summarized. The developmental trend of ART derivatives, and cyclic peroxides along with their antimalarial activity and how the activity is affected by structural variations on different sites of the compounds are discussed. This compilation would be very useful towards scaffold hopping aimed at avoiding the unnecessary complexity in cyclic peroxides, and ultimately act as a handy resource for the development of potential chemotherapeutics against Plasmodium species.

Medicinal chemistry updates on quinoline- and endoperoxide-based hybrids with potent antimalarial activity

The resistance of conventional antimalarial drugs against the malarial parasite continues to pose a challenge to control the disease. The indiscriminate exploitation of the available antimalarials has resulted in increasing treatment failures, which urges on the search for novel lead molecules. Artemisinin-based combination therapy (ACT) is the current WHO-recommended first-line treatment for the majority of malaria cases. Hybrid molecules offer a newer strategy for the development of next-generation antimalarial drugs. These comprise molecules, each with an individual pharmacological activity, linked together into a single hybrid molecule. This approach has been utilized by several research groups to develop molecules with potent antimalarial activity. In this review, we provide an overview of the pivotal roles of quinoline- and endoperoxide-based hybrids as inhibitors of the life-cycle progression of Plasmodium. Based on the exhaustive literature reports, we have collated the structural and functional analyses of quinoline- and endoperoxide-based hybrid molecules that show potency equal to or greater than those of the individual compounds, offering an effective therapeutics option for clinical use.

Antimalarial application of quinones: A recent update

Atovaquone belongs to a naphthoquinone class of drugs and is used in combination with proguanil (Malarone) for the treatment of acute, uncomplicated malaria caused by Plasmodium falciparum (including chloroquine-resistant P. falciparum/P. vivax). Numerous quinone-derived compounds have attracted considerable attention in the last few decades due to their potential in antimalarial drug discovery. Several semi-synthetic derivatives of natural quinones, synthetic quinones (naphtho-/benzo-quinone, anthraquinones, thiazinoquinones), and quinone-based hybrids were explored for their in vitro and in vivo antimalarial activities. A careful literature survey revealed that this topic has not been compiled as a review article so far. Therefore, we herein summarise the recent discovery (the year 2009-2020) of quinone based antimalarial compounds in chronological order. This compilation would be very useful towards the exploration of novel quinone-derived compounds against malarial parasites with promising efficacy and lesser side effects.

Structural optimization and biological evaluation for novel artemisinin derivatives against liver and ovarian cancers

An increasing number of artemisinin (ARS) and its derivatives have been reported for their potential therapeutic value of human cancer. However, their therapeutic potencies are limited owing to their poor pharmacokinetic profiles. Our previous studies showed that a lead compound ARS4 originated from incorporating the pharmacophore of the approved chemotherapeutic agent melphalan into the basic skeleton of artemisinin with a succinic linker exhibited an excellent toxicity to human ovarian cancer cells and low cytotoxicity to normal cells. The mechanism studies demonstrated that it inhibited the growth and proliferation of ovarian cancer cells and resulted in S-phase arrest, apoptosis and inhibition of migration. Meanwhile, it exhibited excellent antitumor activities in animal models. Herein, further structure optimization for this lead compound ARS4 was performed and nineteen novel derivatives were designed and synthesized. Among them, compounds 10-12, 15, 16, 18 and 19 demonstrated powerful cytotoxic effects against human liver cancer and ovarian cancer cell lines, with their IC_50s below 0.86 μM against Hep3B and A2780 cell lines, which are superior to that of ARS4. Four compounds (11, 15, 16 and 18) were selected to further evaluate their antitumor activities in in vitro and in vivo ovarian and liver cancer models, the results indicated that compound 18 exhibited the best therapeutic effect, not only effectively inhibited the growth of 7404 xenograft and Huh7 xenograft, but also presented a good dose-dependent inhibition toward the growth of A2780 xenograft. Overall, based on these positive results, these novel chemical structures may provide a new inspiration for the discovery of novel antitumor agents originated from artemisinin scaffolds.

Development of GLUT1-targeting alkyl glucoside-modified dihydroartemisinin liposomes for cancer therapy

The antitumor activity of artemisinin derivatives has attracted much attention. However, lack of tumor targeting limits the anti-tumor activity of artemisinin derivatives. It is reported that tumor cells acquire energy through the glycolysis pathway. To meet their elevated glucose requirements, high expressions of glucose transporters (GLUTs) are observed in many malignant cells. On this basis, novel alkyl glycoside-modified dihydroartemisinin liposomes were successfully prepared with GLUT1 as the target and the glucose segment of an alkyl glycoside as the targeting head on the surface of liposomes. The particle size of the liposomes was 100.67 ± 1.25 nm, zeta potential was -22.93 ± 0.92 mV and encapsulation efficiency was 75.28 ± 0.73%, meanwhile the liposomes had good stability. In vitro targeting of liposomes was evaluated by fluorescence microscopy and flow cytometry. Compared with human L02 hepatocyte cells, the liposomes showed better targeting ability to human liver carcinoma cells HepG2 with the help of the glucose segment modified on the liposomes. In vivo targeting evaluation also showed that the tumor targeting of alkyl glycoside-modified liposomes was significantly improved, as well as the anti-tumor activity. These findings provide a research and theoretical basis for the development of artemisinin derivatives and other drug targeted antitumor nano-agents.

The potential of artemisinins as anti-obesity agents via modulating the immune system

Artemisinin and its derivatives are the most effective antimalarial drugs. Besides anti-malarial activity, artemisinin and its derivatives have displayed wide-spectrum bioactivities such as anti-parasite, anti-tumor, and anti-obesity effects. Obesity is an epidemic worldwide which is a big threat to human health, but there are only a few approved anti-obesity drugs in the world. Also, these drugs are efficient to limited patients partly because their safety and efficacy are questioned. Anti-inflammatory therapies may be valuable in obesity treatment since growing evidence shows chronic metabolic inflammation is implicated in metabolic disease pathogenesis. As artemisinin and its derivatives display effective anti-inflammatory and immunoregulatory properties with less toxicity, it provides an insight for novel drug development in obesity therapeutic strategies via immune-regulatory mechanisms. In this review, the potential of artemisinin and its derivatives to treat various metabolic diseases such as obesity and diabetes is discussed.

Treatment of Experimental Cerebral Malaria by Slow Release of Artemisone From Injectable Pasty Formulation

Malaria caused by Plasmodium falciparum causes numerous cases of morbidity with about 400,000 deaths yearly owing, mainly, to inflammation leading to cerebral malaria (CM). CM conventionally is treated by repetitive administration of anti-plasmodial drugs and supportive non-specific drugs, for about a week. A mouse model of CM caused by Plasmodium berghei ANKA, in which brain and systemic clinical pathologies occur followed by sudden death within about a week, was used to study the effect of artemisone, a relatively new artemisinin, within an injectable pasty polymer formulated for its controlled release. The parasites were exposed to the drug over several days at a non-toxic concentrations for the mice but high enough to affect the parasites. Artemisone was also tested in cultures of bacteria, cancer cells and P. falciparum to evaluate the specificity and suitability of these cells for examining the release of artemisone from its carrier. Cultures of P. falciparum were the most suitable. Artemisone released from subcutaneous injected poly(sebacic acid-ricinoleic acid) (PSARA) pasty polymer, reduced parasitemias in infected mice, prolonged survival and prevented death in most of the infected mice. Successful prophylactic treatment before infection proved that there was a slow release of the drug for about a week, which contrasts with the three hour half-life that occurs after injection of just the drug. Treatment with artemisone within the polymer, even at a late stage of the disease, helped to prevent or, at least, delay accompanying severe symptoms. In some cases, treatment prevented death of CM and the mice died later of anemia. Postponing the severe clinical symptoms is also beneficial in cases of human malaria, giving more time for an appropriate diagnosis and treatment before severe symptoms appear. The method presented here may also be useful for combination therapy of anti-plasmodial and immunomodulatory drugs.

Rosmarinic acid reverses non-small cell lung cancer cisplatin resistance by activating the MAPK signaling pathway

Cisplatin (DDP) is one of the first-line chemotherapeutic agents for non-small cell lung cancer (NSCLC). However, repeated use of cisplatin in clinical practice often induces chemoresistance. The aims of this study were to investigate whether rosmarinic acid (RA) could reverse multidrug resistance (MDR) in NSCLC and to explore the underlying mechanisms. Our data demonstrated that RA significantly inhibited NSCLC cell proliferation and cell colony formation in a dose-dependent manner, induced G1 phase cell cycle arrest and apoptosis, and increased the sensitivity of cell lines resistant to DDP. Mechanistically, RA inhibited NSCLC cell growth, arrested cell cycle, and induced apoptosis by activating MAPK and inhibiting the expression of P-gp and MDR1, which correspondingly enhanced p21 and p53 expression. We observed that the growth of xenograft tumors derived from NSCLC cell lines in nude mice was significantly inhibited by combination therapy. We demonstrate that RA is a potentially effective MDR reversal agent for NSCLC, based on downregulation of MDR1 mRNA expression and P-gp. Together, these results emphasize the putative role of RA as a resistance reversal agent in NSCLC.

Fluorinated scaffolds for antimalarial drug discovery

INTRODUCTION

The unique physicochemical properties and chemical diversity of organofluorine compounds have remarkably contributed for their wide utility in the area of pharmaceuticals, materials and agrochemicals. The noteworthy characteristics of fluorine include high electron affinity, lipophilicity and bioavailability, extending the half-life of the drugs. The incorporation of fluorine substituents, particularly trifluoromethyl groups, into organic molecules has led to their high potency against various diseases, including malaria. Hence, organofluorinated molecules offer valuable avenues for the design of new drug candidates against malaria.

AREAS COVERED

In this review, the authors discuss the importance of fluorine substituents present in the chemical compounds, and their potential applications for antimalarial drug discovery.

EXPERT OPINION

Fluorinated molecules represent a reliable strategy to develop new antimalarial drugs. Fluorine or fluorinated groups have been identified as a promising precursor, and their presence in approximately twenty-five percent of approved drugs is notable. Selective fluorination of chemical entities has the potential to be applied not only to improve the activity profile against the malaria parasite, but could be extrapolated for favorable pharmacological applications. Hazardous reagents such as HF, F₂ and SF₄ used for fluorination, are not considered as safe, and therefore, this process remains challenging, particularly for the pharmaceutical industry.

Chalcone hybrids and their antimalarial activity

Malaria, one of the most striking, re-emerging infectious diseases caused by the genus Plasmodium, places a huge burden on global healthcare systems. A major challenge in the control and eradication of malaria is the continuous emergence of increasingly widespread drug-resistant malaria, creating an urgent need to develop novel antimalarial agents. Chalcone derivatives are ubiquitous in nature and have become indispensable units in medicinal chemistry applications due to their diverse biological profiles. Many chalcone derivatives demonstrate potential in vitro and in vivo antimalarial activity, so chalcone could be a useful template for the development of novel antimalarial agents. This review covers the recent development of chalcone hybrids as antimalarial agents. The critical aspects of the design and structure-activity relationship of these compounds are also discussed.

Artemisinin-derived antimalarial endoperoxides from bench-side to bed-side: Chronological advancements and future challenges

According to WHO World Malaria Report (2018), nearly 219 million new cases of malaria occurred and a total no. of 435 000 people died in 2017 due to this infectious disease. This is due to the rapid spread of parasite-resistant strains. Artemisinin (ART), a sesquiterpene lactone endoperoxide isolated from traditional Chinese herb Artemisia annua, has been recognized as a novel class of antimalarial drugs. The 2015 "Nobel Prize in Physiology or Medicine" was given to Prof Dr Tu Youyou for the discovery of ART. Hence, ART is termed as "Nobel medicine." The present review article accommodates insights from the chronological advancements and direct statistics witnessed during the past 48 years (1971-2019) in the medicinal chemistry of ART-derived antimalarial endoperoxides, and their clinical utility in malaria chemotherapy and drug discovery.