Antimalarials from nature

Diastereoselective synthesis of functionalized spiroindolines via intramolecular ipso-iodocyclization/nucleophile addition cascade reactions of indole-tethered ynones

Herein, we describe a highly diastereoselective approach for synthesizing polyfunctionalized spiroindolines from indolyl-ynones involving an ipso-iodocyclization/nucleophile addition cascade. The developed strategy allows the formation of a spirocyclic core and the installation of two functional groups in a single operation. Also this strategy is accompanied by the generation of two C-C and one C-I bonds and two contiguous stereocenters.

Evaluation of the antiplasmodial efficacy of synthetic 2,5-diphenyloxazole analogs of compounds naturally derived from Oxytropis lanata

The persistent prevalence and dissemination of drug-resistant malaria parasites continue to challenge the progress of malaria eradication efforts. As a result, there is an urgent need to search for and develop innovative therapies. In this study, we screened synthetic 2,5-diphenyloxazole analogs from Oxytropis lanata. Among 48 compounds, 14 potently inhibited the proliferation of P. falciparum strains 3D7 (chloroquine-sensitive) and K1 (multidrug-resistant) in vitro, exhibited IC50 values from 3.38 to 12.65 μM and 1.27-6.19 μM, respectively, and were toxic to human foreskin fibroblasts at 39.53-336.35 μM. Notably, Compounds 31 (2-(2',3'-dimethoxyphenyl)-5-(2″-hydroxyphenyl)oxazole) and 32 (2-(2',3'-dimethoxyphenyl)-5-(2″-benzyloxyphenyl)oxazole) exhibited the highest selectivity indices (SIs) against both P. falciparum strains (3D7/K1), with values > 40.20/>126.58 and > 41.27/> 59.06, respectively. In the IC50 speed and stage-specific assays, Compounds 31 and 32 showed slow action, along with distinct effects on the ring and trophozoite stages. Microscopy observations further revealed that both compounds impact the development and delay the progression of the trophozoite and schizont stages in P. falciparum 3D7, especially at concentrations 100 times their IC50 values. In a 72-h in vitro exposure experiment at their respective IC80 in P. falciparum 3D7, significant alterations in parasitemia levels were observed compared to the untreated group. In Compound 31-treated cultures, parasites shrank and were unable to reinvade red blood cells (RBCs) during an extended 144-h incubation period, even after compound removal from the culture. In vivo assessments were conducted on P. yoelii 17XNL-infected mice treated with Compounds 31 and 32 at 20 mg/kg administered once daily for ten days. The treated groups showed statistically significant lower peaks of parasitemia (Compound 31-treated: trial 1 12.7%, trial 2 15.8%; Compound 32-treated: trial 1 12.7%, trial 2 14.0%) compared to the untreated group (trial 1 21.7%, trial 2 28.3%). These results emphasize the potential of further developing 2,5-diphenyloxazoles as promising antimalarial agents.

Chemoproteomics-based profiling reveals potential antimalarial mechanism of Celastrol by disrupting spermidine and protein synthesis

BACKGROUND

Malaria remains a global health burden, and the emergence and increasing spread of drug resistance to current antimalarials poses a major challenge to malaria control. There is an urgent need to find new drugs or strategies to alleviate this predicament. Celastrol (Cel) is an extensively studied natural bioactive compound that has shown potentially promising antimalarial activity, but its antimalarial mechanism remains largely elusive.

METHODS

We first established the Plasmodium berghei ANKA-infected C57BL/6 mouse model and systematically evaluated the antimalarial effects of Cel in conjunction with in vitro culture of Plasmodium falciparum. The potential antimalarial targets of Cel were then identified using a Cel activity probe based on the activity-based protein profiling (ABPP) technology. Subsequently, the antimalarial mechanism was analyzed by integrating with proteomics and transcriptomics. The binding of Cel to the identified key target proteins was verified by a series of biochemical experiments and functional assays.

RESULTS

The results of the pharmacodynamic assay showed that Cel has favorable antimalarial activity both in vivo and in vitro. The ABPP-based target profiling showed that Cel can bind to a number of proteins in the parasite. Among the 31 identified potential target proteins of Cel, PfSpdsyn and PfEGF1-α were verified to be two critical target proteins, suggesting the role of Cel in interfering with the de novo synthesis of spermidine and proteins of the parasite, thus exerting its antimalarial effects.

CONCLUSIONS

In conclusion, this study reports for the first time the potential antimalarial targets and mechanism of action of Cel using the ABPP strategy. Our work not only support the expansion of Cel as a potential antimalarial agent or adjuvant, but also establishes the necessary theoretical basis for the development of potential antimalarial drugs with pentacyclic triterpenoid structures, as represented by Cel. Video Abstract.

Effects of Radix dichroae extract supplementation on growth performance, oocysts output and gut microbiota in growing lambs with coccidiosis

Coccidiosis is an intestinal protozoan disease of sheep, that causes substantial economic losses in the industry due to its intestinal protozoan origins. Many anti-protozoan drugs including ionophores, triazines, and sulfonamides have been widely used to treat sheep coccidiosis. Still, anticoccidial resistance and drug residues in edible tissues have prompted an urgent search for alternatives. In this study, the anti-coccidial effectiveness of the Radix dichroae extract was compared to that of the conventional anti-coccidial drug diclazuril. Here, eighteen 45-day-old lambs naturally-infected with Eimeria spp. were randomly allocated in three groups: control group, Radix dichroae extract group and diclazuril group. The results showed that the body weight gain (BWG) during the treatment and withdrawal periods was considerably improved in the coccidiosis-infected sheep treated with Radix dichroae extract and diclazuril compared to the control group, respectively. Additionally, the Radix dichroae extract and diclazuril had fewer oocysts per gram (OPG) than the control group, showing similar anti-coccidial effects on days 14, 21, 28, 35 and 78, respectively. Furthermore, Radix dichroae extract and diclazuril treatment altered the structure and composition of gut microbiota, promoting the relative abundance of Actinobacteriota, Firmicutes, Alistipes, and Bifidobacterium, while decreasing the abundance of Bacteroidota, Marinilaceae, Helicobacteraceae, and Prevotella. Moreover, Spearman's correlation analysis further revealed a correlation between the OPG and BWG and gut microorganisms. Collectively, the results indicated that Radix dichroae extract had similar anti-coccidial effects as diclazuril, and could regulate gut microbiota balance in growing lambs.

A Sequential Transition Metal and Organocatalytic Approach to the Enantioselective Synthesis of C2-Spiroindoline Systems

We report herein an organocatalyzed enantioselective spirocyclization strategy to access valuable C2-spiroindoline scaffolds bearing a quaternary stereocenter via an aza-Michael addition reaction, wherein the acid additive plays the role of dual functionality. The substrates for this key step were put together by an exo-selective, Pd-catalyzed γ-arylation of silyldienol ethers of the corresponding cyclohexenones. A close alliance between a low catalyst loading and a slow reaction rate yields C2-spiroindolines with good enantioselectivity.

Potentials of Terpenoids as Inhibitors of Multiple Plasmodium falciparum Protein Drug Targets

PURPOSE

The resistance of parasite to readily affordable antimalarial drugs, the high cost of currently potent drugs, and the resistance of vector mosquitoes to insecticides threaten the possibility of malaria eradication in malaria endemic areas. Due to the fact that quinine and artemisinin were isolated from plants sources, researchers have been encouraged to search for new antimalarials from medicinal plants. This is especially the case in Africa where a large percentage of the population depends on medicinal plant to treat malaria and other ailments.

METHOD

In this study, we evaluated previously characterized Plasmodium-cidal compounds obtained from the African flora to identify their likely biochemical targets, for an insight into their possible antimalarial chemotherapy. Molecular docking study was first conducted, after which remarkable compounds were submitted for molecular dynamic (MD) simulations studies.

RESULTS

From a total of 38 Plasmodium-cidal compounds docked with confirmed Plasmodium falciparum protein drug targets [plasmepsin II (PMII), histo-aspartic protein (HAP) and falcipain-2 (FP)], two pentacyclic triterpene, cucurbitacin B and 3 beta-O-acetyl oleanolic acid showed high binding affinity relative to artesunate. This implies their capacity to inhibit the three selected P. falciparum target proteins, and consequently, antimalarial potential. From the MD simulations studies and binding free energy outcomes, results confirmed that the two compounds are stable in complex with the selected antimalarial targets; they also showed excellent binding affinities during the 100 ns simulation.

CONCLUSION

These results showed that cucurbitacin B and 3 beta-O-acetyl oleanolic acid are potent antimalarials and should be considered for further studies.

The Potentials of Ageratum conyzoides and Other Plants from Asteraceae as an Antiplasmodial and Insecticidal for Malaria Vector: An Article Review

Background

Malaria is a life-threatening disease prevalent in tropical and subtropical regions. Artemisinin combination therapy (ACT) used as an antimalarial treatment has reduced efficacy due to resistance, not only to the parasite but also to the vector. Therefore, it is important to find alternatives to overcome malaria cases through medicinal plants such as Ageratum conyzoides and other related plants within Asteraceae family.

Purpose

This review summarizes the antimalarial and insecticidal activities of A. conyzoides and other plants belonging to Asteraceae family.

Data Source

Google Scholar, PubMed, Science Direct, and Springer link.

Study Selection

Online databases were used to retrieve journals using specific keywords combined with Boolean operators. The inclusion criteria were articles with experimental studies either in vivo or in vitro, in English or Indonesian, published after 1st January 2000, and full text available for inclusion in this review.

Data Extraction

The antimalarial activity, insecticidal activity, and structure of the isolated compounds were retrieved from the selected studies.

Data Synthesis

Antimalarial in vitro study showed that the dichloromethane extract was the most widely studied with an IC50 value <10 μg/mL. Among 84 isolated active compounds, 2-hydroxymethyl-non-3-ynoic acid 2-[2,2']-bithiophenyl-5- ethyl ester, a bithienyl compound from the Tagetes erecta plant show the smallest IC50 with value 0.01 and 0.02 µg/mL in Plasmodium falciparum MRC-pf-2 and MRC-pf-56, respectively. In vivo studies showed that the aqueous extract of A. conyzoides showed the best activity, with a 98.8% inhibition percentage using a 100 mg/kg dose of Plasmodium berghei (NK65 Strain). (Z)- γ-Bisabolene from Galinsoga parviflora showed very good insecticidal activity against Anopheles stephensi and Anopheles subpictus with LC50 values of 2.04 μg/mL and 4.05 μg/mL.

Conclusion

A. conyzoides and other plants of Asteraceae family are promising reservoirs of natural compounds that exert antimalarial or insecticidal activity.

Deciphering anti-infectious compounds from Peruvian medicinal Cordoncillos extract library through multiplexed assays and chemical profiling

High prevalence of parasitic or bacterial infectious diseases in some world areas is due to multiple reasons, including a lack of an appropriate health policy, challenging logistics and poverty. The support to research and development of new medicines to fight infectious diseases is one of the sustainable development goals promoted by World Health Organization (WHO). In this sense, the traditional medicinal knowledge substantiated by ethnopharmacology is a valuable starting point for drug discovery. This work aims at the scientific validation of the traditional use of Piper species ("Cordoncillos") as firsthand anti-infectious medicines. For this purpose, we adapted a computational statistical model to correlate the LCMS chemical profiles of 54 extracts from 19 Piper species to their corresponding anti-infectious assay results based on 37 microbial or parasites strains. We mainly identified two groups of bioactive compounds (called features as they are considered at the analytical level and are not formally isolated). Group 1 is composed of 11 features being highly correlated to an inhibiting activity on 21 bacteria (principally Gram-positive strains), one fungus (C. albicans), and one parasite (Trypanosoma brucei gambiense). The group 2 is composed of 9 features having a clear selectivity on Leishmania (all strains, both axenic and intramacrophagic). Bioactive features in group 1 were identified principally in the extracts of Piper strigosum and P. xanthostachyum. In group 2, bioactive features were distributed in the extracts of 14 Piper species. This multiplexed approach provided a broad picture of the metabolome as well as a map of compounds putatively associated to bioactivity. To our knowledge, the implementation of this type of metabolomics tools aimed at identifying bioactive compounds has not been used so far.

Pathways to healing: Plants with therapeutic potential for neurodegenerative diseases

Some of the greatest challenges in medicine are the neurodegenerative diseases (NDs), which remain without a cure and mostly progress to death. A companion study employed a toolkit methodology to document 2001 plant species with ethnomedicinal uses for alleviating pathologies relevant to NDs, focusing on its relevance to Alzheimer's disease (AD). This study aimed to find plants with therapeutic bioactivities for a range of NDs. 1339 of the 2001 plant species were found to have a bioactivity from the literature of therapeutic relevance to NDs such as Parkinson's disease, Huntington's disease, AD, motor neurone diseases, multiple sclerosis, prion diseases, Neimann-Pick disease, glaucoma, Friedreich's ataxia and Batten disease. 43 types of bioactivities were found, such as reducing protein misfolding, neuroinflammation, oxidative stress and cell death, and promoting neurogenesis, mitochondrial biogenesis, autophagy, longevity, and anti-microbial activity. Ethno-led plant selection was more effective than random selection of plant species. Our findings indicate that ethnomedicinal plants provide a large resource of ND therapeutic potential. The extensive range of bioactivities validate the usefulness of the toolkit methodology in the mining of this data. We found that a number of the documented plants are able to modulate molecular mechanisms underlying various key ND pathologies, revealing a promising and even profound capacity to halt and reverse the processes of neurodegeneration.

Ethnobotany, botany, phytochemistry and ethnopharmacology of the genus Thalictrum L. (Ranunculaceae): A review

ETHNOPHARMACOLOGICAL RELEVANCE

Thalictrum (Ranunculaceae) is known for its important alkaloids which have been reported to exhibit various pharmacological activities, viz. antitumor, antimicrobial, antitussive, antiamebic, hypotensive effects, HIV antiviral, etc. Throughout the world, the plant has been used as a tonic, purgative, stimulant, aperient and is utilized in various systems of medicine in the treatment of various ailments like snake bite, jaundice, rheumatism, stomachache, wounds, swellings, uterine tumors, paralysis, joints pain, nervous disorders, toothache, diarrhea, piles, fever, peptic ulcer, ophthalmic, headache, diuretic, dyspepsia, convalescence, etc. AIMS OF THIS REVIEW: To bring together all the information regarding the botany, phytochemistry, ethnobotany and ethnopharmacology of Thalictrum and identify the gaps in the existing studies so that full medicinal potential of the genus can be realized.

METHODS

Available literature on botany, geography, traditional uses, phytochemicals, and pharmacology was gathered by referring to library and electronic searches in PubMed, Science Direct, Google Scholar, relevant journals and books.

RESULTS

A variety of phytochemicals like alkaloids, essential oils, glycosides, phenols and terpenoids have been reported from Thalictrum species. Alkaloids are the most dominant diverse group with 178 different types. The crude extracts and isolates exhibit a gamut of pharmacological activities, namely anticancer, antimalarial, antioxidant, antipyretic, anti-tumor, ant-influenza virus, contraceptive and immunosuppressive. Northalrugosidine, an alkaloid from T. alpinum shows in vivo antileishmanial activity. So far, cytotoxic effects of only three Thalictrum species, viz. T. dasycarpum, T. foliolosum and T. simplex have been reported. Thl isolated from T. simplex is found to be 50% toxic (CC50%) at the concentration ranging from 53 to 95 μM.

CONCLUSIONS

Thalictrum has tremendous medicinal values used in many traditional systems of medicine. It has multiple chemical components and still there is scope to explore more. Multiple chemical constituents and its utilization signify its high demand in the drug markets or pharmaceutical companies. In depth phytochemical studies along with in vitro studies with respect to their active principles can help in tapping the full medicinal potential of the genus.

Nutritional, antioxidant, and antimicrobial assessment of carrot powder and its application as a functional ingredient in probiotic soft cheese

Carrots (the main source of carotenoids) have multiple nutritional and health benefits. The objectives of this study were to evaluate the compositional, antioxidant, and antimicrobial properties of carrot powder and to examine its effect on the sensory characteristics, chemical properties, and microbial viability of probiotic soft cheese at a rate of 0.2, 0.4, and 0.6%. The carrot was turned into powder before being analyzed and incorporated as an ingredient in making probiotic soft cheese. Probiotic soft cheese was made from buffalo milk. The buffalo milk (∼6.9% fat, 4.4% protein, 9.2% milk solids not fat, and 0.7% ash) was pasteurized at 75 ± 1°C for 5 min and cooled to 40-42°C. The milk was then divided into 4 aliquots. Sodium chloride (local market, Assiut, Egypt) was added at a ratio of 5% followed by starter cultures. The carrot powder (4.5% moisture, 4.8% ash, 2.7% fat, 8.2% protein, 11.9% fibers, and 72.3% carbohydrate) was added at a rate of 0.2, 0.4, and 0.6%, followed by addition of 0.02 g/kg rennet. The cheese was cut again into cubes, pickled in jars filled with whey, and stored for 28 d at 6 ± 1°C. The results of this study illustrated the nutritional and antioxidant properties of carrot powder. Incorporation of carrot powder in probiotic soft cheese affected the moisture and salt content at 0 d. The total bacteria count decreased from 7.5 to 7.3 log cfu/g in the cheese when carrot powder was used at a rate of 0.6%. The reduction of total bacteria count was noticed during the 28 d of storage by adding carrot powder. Furthermore, lactic acid bacteria and Bifidobacterium longum counts elevated with adding carrot powder during the 28 d of storage.

Ethnobotanical uses, phytochemistry and pharmacology of pantropical genus Zanthoxylum L. (Rutaceae): An update

ETHNOPHARMACOLOGICAL RELEVANCE

Plants have been used in various parts of the world to treat various diseases. The genus Zanthoxylum L. (Rutaceae) is the second largest genus of this family and comprises approximately 225-549 species distributed in the tropical and temperate regions of the world. Plants of this genus are trees and shrubs with various applications in folklore medicine for food, medicine, construction, and other uses.

AIM OF THE REVIEW

The goal of this review is to give an updated data on the ethnobotanical applications, phytochemistry, and pharmacology of the Zanthoxylum species to investigate their medicinal potential and identify research gaps for future research studies.

MATERIALS AND METHODS

Data was obtained through a systematic search of published literature and online databases such as Google Scholar, Web of Science, PubMed, Science Direct, and Sci-Finder. The botanical names were confirmed using the World Flora Online and chemical structures were drawn using the ChemBio Draw Ultra Version 14.0 Software.

RESULTS

The Zanthoxylum species have a wide use in different parts of the continents as a remedy for various diseases such as digestive diseases, gastrointestinal disorders, venereal diseases, respiratory diseases, rheumatism, bacterial diseases, viral, and other diseases. Various parts of the plant comprising fruits, seeds, twigs, leaves, oils, and stems are administered singly or in the form of decoction, infusion, powder, paste, poultice, juice, or mixed with other medicinal plants to cure the disease. More than 400 secondary metabolites have been isolated and characterized in this genus with various biological activities, which comprise alkaloids, flavonoids, coumarins, lignans, alcohols, fatty acids, amides, sesquiterpenes, monoterpenes, and hydrocarbons. The crude extracts, fractions, and chemical compounds isolated from the genus have demonstrated a wide range of biological activities both in vivo and in vitro, including; anti-cancer, antimicrobial, anti-sickling, hepatoprotective, antipyretic, antitumor, and other pharmacological activities.

CONCLUSION

This genus has demonstrated an array of phytoconstituents with therapeutic potential. The ethnobotanical uses of this genus have been confirmed in modern pharmacological research. This genus is a potential source for modern drug discovery and health care products. Further and extensive research is therefore required on the safety approval and therapeutic application of the species of this genus as well as clinical trials and pharmacokinetic studies.

Antiplasmodial activity of coumarins isolated from Polygala boliviensis: in vitro and in silico studies

Polygala boliviensis is found in the Brazilian semiarid region. This specie is little chemically and biologically studied. Polygala spp. have different metabolites, especially coumarins. Studies indicate that coumarins have antimalarial potential, denoting the importance of researching new active compounds from plants, since the resistance of Plasmodium strains to conventional therapy has increased. The present study aimed to evaluate the antiplasmodial activity of auraptene and poligalen against a chloroquine-resistant strain of Plasmodium falciparum. Coumarins were isolated from P. boliviensis by open column chromatography and identified by Nuclear Magnetic Resonance Spectroscopy. A cytotoxicity assay was carried out using MTT test, and the in vitro antiplasmodial activity was evaluated using the W2 strain. The antiplasmodial activity results found were IC50=0.171 ± 0.016 for auraptene and 0.164 ± 0.012 for poligalen; the selectivity indexes were 78.71 and 609.76, respectively. Inverse virtual screening in the BRAMMT database by OCTOPUS 1.2 was applied to coumarins to find potential P. falciparum targets and showed higher affinity energy of auraptene for purine nucleoside phosphorylase (PfPNP) and of poligalen for dihydroorotate dehydrogenase (PfDHODH). Molecular Dynamics studies (MD and MM-GBSA) approach were applied to calculate binding energies against selected P. falciparum targets and showed that all coumarins were stable at the binding site during simulations. Furthermore, energies were favorable for complexation. This is the first report of auraptene in P. boliviensis species and of in vitro antiplasmodial activity of auraptene and poligalen. In silico studies indicated that the mechanism of action of coumarins is the inhibition of PfPNP and PfDHODH.Communicated by Ramaswamy H. Sarma.

Evaluation of Antimalarial Activity of Ethanolic Extract of Annona muricata L.: An in vivo and an in silico Approach

In Nigeria, Annona muricata L. has been used to treat a variety of ailments. The mechanism of the antimalarial activity of ethanolic leaf extract of Annona muricata (EEAML) was investigated using both an in vivo and an in silico approach. The experimental mice were divided into five groups: A-F. The mice in groups B-F were inoculated with Plasmodium berghei NK-65 and treated accordingly. Groups A and B are the negative and positive controls (infected and untreated), respectively. Group C received 10 mg/kg chloroquine (standard drug), whereas groups D-F received 100, 200, and 300 mg/kg body weight of the extract orally respectively. The mice were euthanized eight days after infection, and their liver and blood were collected and used in biochemical tests. Molecular docking was performed using the extract's HPLC compounds and Plasmodium falciparum proteins. In the suppressive, prophylactic, and curative tests, there was a significant decrease (p < 0.05) in parasitemia levels in groups treated with the extract compared to the positive control and standard drug. When compared to the positive control, there was a significant (p < 0.05) reduction in liver MDA, total cholesterol, and total triglyceride levels. The binding energies of luteolin and apigenin-pfprotein complexes were significantly (p < 0.05) higher compared to their respective references. The anti-plasmodial activity of the extract may result from its hypolipidemic effect, which deprives the parasite of essential lipid molecules needed for parasite growth, as well as from the inhibitory effects of apigenin and luteolin on specific proteins required for the Plasmodium metabolic pathway.

Structure- and ligand-based drug design methods for the modeling of antimalarial agents: a review of updates from 2012 onwards

Malaria still persists as one of the deadliest infectious disease having a huge morbidity and mortality affecting the higher population of the world. Structure and ligand-based drug design methods like molecular docking and MD simulations, pharmacophore modeling, QSAR and virtual screening are widely used to perceive the accordant correlation between the antimalarial activity and property of the compounds to design novel dominant and discriminant molecules. These modeling methods will speed-up antimalarial drug discovery, selection of better drug candidates for synthesis and to achieve potent and safer drugs. In this work, we have extensively reviewed the literature pertaining to the use and applications of various ligand and structure-based computational methods for the design of antimalarial agents. Different classes of molecules are discussed along with their target interactions pattern, which is responsible for antimalarial activity. Communicated by Ramaswamy H. Sarma.

Lead/Drug Discovery from Natural Resources

Natural products and their derivatives have been shown to be effective drug candidates against various diseases for many years. Over a long period of time, nature has produced an abundant and prosperous source pool for novel therapeutic agents with distinctive structures. Major natural-product-based drugs approved for clinical use include anti-infectives and anticancer agents. This paper will review some natural-product-related potent anticancer, anti-HIV, antibacterial and antimalarial drugs or lead compounds mainly discovered from 2016 to 2022. Structurally typical marine bioactive products are also included. Molecular modeling, machine learning, bioinformatics and other computer-assisted techniques that are very important in narrowing down bioactive core structural scaffolds and helping to design new structures to fight against key disease-associated molecular targets based on available natural products are considered and briefly reviewed.

Phytochemical, Antimalarial, and Acute Oral Toxicity Properties of Selected Crude Extracts of Prabchompoothaweep Remedy in Plasmodium berghei-Infected Mice

Malaria remains a life-threatening health problem and encounters with the increasing of antimalarial drug resistance. Medicinal plants play a critical role in synthesizing novel and potent antimalarial agents. This study aimed to investigate the phytochemical constituents, antiplasmodial activity, and evaluate the toxicity of crude ethanolic extracts of Myristica fragrans, Atractylodes lancea, and Prabchompoothaweep remedy in a mouse model. The phytochemical constituents were characterized by liquid chromatography-mass spectrometry (LC-MS). Antimalarial efficacy against Plasmodium berghei was assessed using 4-day suppressive tests at doses of 200, 400, and 600 mg/kg body weight. Acute toxicity was assessed at a dose of 2000 mg/kg body weight of crude extracts. The 4-day suppression test showed that all crude extracts significantly suppressed parasitemia (p < 0.05) compared to the control group. Higher parasitemia suppression was observed both in Prabchompoothaweep remedy at a dose of 600 mg/kg (60.1%), and A. lancea at a dose of 400 mg/kg (60.1%). The acute oral toxicity test indicated that the LD50 values of all extracts were greater than 2000 mg/kg and that these extracts were not toxic in the mouse model. LC-MS analysis revealed several compounds in M. fragrans, A. lancea, and Prabchompoothaweep remedy. For quantitative analysis, 1,2,6,8-tetrahydroxy-3-methylanthraquinone 2-O-b-D-glucoside, chlorogenic acid, and 3-O-(beta-D-glucopyranosyl-(1->6)-beta-D-glucopyranosyl) ethyl 3-hydroxyoctanoate were found in A. lancea, while (7′x,8′x)-4,7′-epoxy-3,8′-bilign-7-ene-3,5′-dimethoxy-4′,9,9′-triol, edulisin III, and tetra-hydrosappanone A trimethyl ether are found in M. fragrans. 6′-O-Formylmarmin was present in the Prabchompoothaweep remedy, followed by pterostilbene glycinate and amlaic acid. This study showed that the ethanolic extracts of A. lancea and Prabchompoothaweep remedy possess antimalarial activity against Plasmodium berghei. None of the extracts had toxic effects on liver and kidney function. Therefore, the ethanolic extract of A. lancea rhizome and Prabchompoothaweep remedy could be used as an alternative source of new antimalarial agents. Further studies are needed to determine the active compounds in both extracts.

Neurotransmitters and molecular chaperones interactions in cerebral malaria: Is there a missing link?

Plasmodium falciparum is responsible for the most severe and deadliest human malaria infection. The most serious complication of this infection is cerebral malaria. Among the proposed hypotheses that seek to explain the manifestation of the neurological syndrome in cerebral malaria is the vascular occlusion/sequestration/mechanic hypothesis, the cytokine storm or inflammatory theory, or a combination of both. Unfortunately, despite the increasing volume of scientific information on cerebral malaria, our understanding of its pathophysiologic mechanism(s) is still very limited. In a bid to maintain its survival and development, P. falciparum exports a large number of proteins into the cytosol of the infected host red blood cell. Prominent among these are the P. falciparum erythrocytes membrane protein 1 (PfEMP1), P. falciparum histidine-rich protein II (PfHRP2), and P. falciparum heat shock proteins 70-x (PfHsp70-x). Functional activities and interaction of these proteins with one another and with recruited host resident proteins are critical factors in the pathology of malaria in general and cerebral malaria in particular. Furthermore, several neurological impairments, including cognitive, behavioral, and motor dysfunctions, are known to be associated with cerebral malaria. Also, the available evidence has implicated glutamate and glutamatergic pathways, coupled with a resultant alteration in serotonin, dopamine, norepinephrine, and histamine production. While seeking to improve our understanding of the pathophysiology of cerebral malaria, this article seeks to explore the possible links between host/parasite chaperones, and neurotransmitters, in relation to other molecular players in the pathology of cerebral malaria, to explore such links in antimalarial drug discovery.

New structural classes of antimalarials

Malaria remains a major vector borne disease claiming millions of lives worldwide due to infections caused by Plasmodium sp. Discovery and development of antimalarial drugs have previously been dominated majorly by single drug therapy. The malaria parasite has developed resistance against first line and second line antimalarial drugs used in the single drug therapy. This has drawn attention to find ways to alleviate the disease burden supplanted by combination therapy with multiple drugs to overcome drug resistance. Emergence of resistant strains even against the combination therapy has now mandated the revision of the current antimalarial pharmacotherapy. Research efforts of the past decade led to the discovery and identification of several new structural classes of antimalarial agents with improved biological attributes over the older ones. The following is a comprehensive review, addressed to the new structural classes of heterocyclic and natural compounds that have been identified during the last decade as antimalarial agents. Some of the classes included herein contain one or more pharmacophores amalgamated into a single bioactive scaffold as antimalarial agents, which act upon the conventional and novel targets.

Alkaloid Composition and Biological Activities of the Amaryllidaceae Species Ismene amancaes (Ker Gawl.) Herb

Natural products have always played a significant role in the search for new drugs. One of the most relevant alkaloid-containing plant groups is the Amaryllidaceae family, a source of exclusive structures with a wide variety of pharmacological activities. The aim of this work was to determine the alkaloid composition and biological potential of an extract from the bulbs of an endemic Peruvian Amaryllidaceae species Ismene amancaes (Ker Gawl.) Herb. The alkaloid profiling was carried out by GC-MS, which revealed the presence of 13 compounds, 2 of them unidentified. The plant extract was found to contain high amounts of lycoramine, a galanthamine-type alkaloid. The extract also presented low inhibitory potential against the enzymes AChE and BuChE, with IC50 values of 14.6 ± 0.6 and 37.6 ± 1.4 μg·mL−1, respectively, and good to moderate inhibitory activity against the protozoan Plasmodium falciparum strain FCR-3 (chloroquine-resistant), with IC50 values of 3.78 ± 0.3 μg·mL−1. This is the first report of the alkaloid profile of a plant of the Ismene genus, which could be an interesting source of bioactive compounds.

Insights into the molecular basis of some chalcone analogues as potential inhibitors of Leishmania donovani: An integrated in silico and in vitro study

Protozoal infections caused by species belonging to Leishmania donovani complex are responsible for the most severe form of leishmaniasis, especially in Sudan and other developing countries. Drugs commonly used for the treatment of the disease show varying levels of effectiveness and also have associated side effects. Thus, the present work highlights the synthesis of some chalcones to be used as potential anti-leishmanial agents. The activity of the synthesized chalcones has been evaluated against L. donovani. The ADMET profile of the synthesized compounds were tested using various integrated web-based tools. Moreover, in order to investigate the molecular mechanism of action, the chalcone compounds were docked into L. donovani trypanothione reductase (TR) using Autodock 4.0 and molecular dynamics were studies. Eight compounds showed the highest activity against the morphological forms. Among these compounds, chalcones 15 has shown the highest inhibitory effect with IC50 value of 1.1 µM. In addition, pharmacokinetic and toxicological investigations revealed its good oral bioavailability and low toxicity. Furthermore, chalcone 15 was found to interact with high affinity (−13.7 kcal/mol) with TR, an essential enzyme for the leishmanial parasite. Thus, this promising activity against L. donovani supports the use of chalcone 15 as a potential new therapy for visceral leishmaniasis.

First Total Syntheses of Natural Phenanthrene Alkaloids, Uvariopsamine, Noruvariopsamine, 8-Hydroxystephenanthrine, 8-Methoxyuvariopsine, Thalihazine, and Secophoebine, and Their Potential as Antimalarial Agents

The first total syntheses of natural phenanthrene alkaloids, namely, uvariopsamine (1), noruvariopsamine (2), 8-hydroxystephenanthrine (3), 8-methoxyuvariopsine (4), thalihazine (5), and secophoebine (6), have been realized. In addition, their in vitro antimalarial activity against the multidrug-resistant K1 strain of Plasmodium falciparum and in vitro cytotoxic activity against the human nasopharynx carcinoma (KB), small cell lung cancer (NCI-H187), and breast cancer (MCF7) human cancer cell lines were investigated. All the phenanthrene alkaloids showed significant antiplasmodial activity (IC₅₀ 1.07-7.41 µM), and most compounds displayed low to no toxicity against the three cancer cell lines tested. Particularly, 3 exhibited the best antimalarial activity with an IC₅₀ value of 1.07 µM, no toxicity to NCI-H187 (IC₅₀ > 50 µM), and low toxicity against KB (IC₅₀ 24.53 µM) and MCF7 (IC₅₀ 42.67 µM) cell lines.

Antiplasmodial and cytotoxic effects of the methanol extract, canthinone alkaloids, squalene- and protolimonoid-type triterpenes from Homalolepis suffruticosa roots

ETHNOPHARMACOLOGICAL RELEVANCE

Different species of the Simaroubaceae family are used in traditional medicine to treat malaria. Among these is Homalolepis suffruticosa (syn. Simaba suffruticosa and Quassia suffruticosa), which is native to Central Brazil and popularly known as calunga. However, there is a lack of investigation concerning its antimalarial effects.

AIM OF THE STUDY

To investigate the antiplasmodial and cytotoxic effects of the isolated metabolites and methanol extract from H. suffruticosa roots as well as to conduct the dereplication of this extract aiming to characterize its metabolic profile by UPLC-DAD-ESI-MS/MS.

MATERIALS AND METHODS

Methanol extract of the H. suffruticosa roots and six isolated compounds were evaluated against chloroquine-resistant Plasmodium falciparum W2 strain by the PfLDH method and cytotoxicity in HepG2 cells by the MTT assay. Dereplication of the extract was performed by UPLC-DAD-ESI-MS/MS.

RESULTS

The six isolated compounds disclosed high to moderate antiplasmodial activity (IC₅₀ 0.0548 ± 0.0083 μg/mL to 26.65 ± 2.40 μg/mL) and cytotoxicity was in the range of CC₅₀ 0.62 ± 0.33 μg/mL to 56.43 ± 2.54 μg/mL, while 5-metoxycantin-6-one proved to be the most potent constituent of the six assayed ones. The methanol extract of the roots showed high in vitro antiplasmodial activity (IC₅₀ 1.88 ± 0.56 μg/mL), moderate cytotoxicity (CC₅₀ 41.93 ± 2.30 μg/mL), and good selectivity index (SI = 22.30). Finally, C₂₀ quassinoids and canthin-6-one alkaloids were putatively identified in the H. suffruticosa methanol extract by LC-MS.

CONCLUSIONS

Taken together, the isolated compounds, mainly the 5-metoxycantin-6-one and the methanol extract from H. suffruticosa roots, disclose good antiplasmodial activity, supporting the ethnopharmacological history of the Simaroubaceae species as traditional antimalarial drugs.

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.

Asymmetric synthesis of polycyclic spiroindolines via the Dy-catalyzed cascade reaction of 3-(2-isocyanoethyl)indoles with aziridines

An asymmetric cascade reaction catalyzed by a chiral N,N′-dioxide–Dy(iii) complex was realized to construct the valuable [6,5,5,6] tetracyclic spiroindolines with good yields and enantioselectivities by a concise and one-step protocol.

Intermolecular interactions in the solid-state structures of isoflavones: the relationship between supramolecular structure, torsion angle, and macroscopic properties

The different macroscopic properties of closely related isoflavones were associated with the occurrence of intermolecular interactions and different torsion angles in the solid-state.

Palladium-catalysed imidoylative spirocyclization of 3-(2-isocyanoethyl)indoles

A palladium-catalysed construction of spiroindolines through dearomative spirocyclization of 3-(2-isocyanoethyl)indoles has been developed. 2'-Aryl-, vinyl-, and alkyl-substituted spiroindolines could be accessed under mild conditions with excellent functional group tolerance. C1-tethered oxindole- and indole-spiroindoline bisheterocycles were generated in high yields via alkene/allene insertion and an imidoylative spirocyclization cascade. Additionally, a tandem dearomatization of two different indoles was realized with N-(2-bromobenzoyl)indoles as the electrophilic coupling partner of 3-(2-isocyanoethyl)indoles, affording polyindoline - spiroindoline bisheterocyclic scaffolds conveniently. Under the catalysis of Pd(OAc)₂ and a spinol-derived phosphoramidite ligand, chiral spiroindolines were successfully accessed with up to 95% yield and 85% ee.

Scope and Applications of 2,3-Oxidative Aryl Rearrangements for the Synthesis of Isoflavone Natural Products

The reaction of flavanones with hypervalent iodine reagents was investigated with a view to the synthesis of naturally occurring isoflavones. In contrast to several previous reports in the literature, we did not observe the formation of any benzofurans via a ring contraction pathway, but could isolate only isoflavones, resulting from an oxidative 2,3-aryl rearrangement, and flavones, resulting from an oxidation of the flavanones. Although the 2,3-oxidative rearrangement allows a synthetically useful approach toward some isoflavone natural products due to the convenient accessibility of the required starting materials, the overall synthetic utility and generality of the reaction appear to be more limited than previous literature reports suggest.

Therapeutic Potential of Genus Pongamia and Derris: Phytochemical and Bioactivity

Genus Pongamia and Derris belong to the Leguminosae family and are reported synonymously in literature. Although many compounds have been isolated from different plant parts but seed oil is known to produce non-edible medicinally important furanoflavonoids. The seed oil, commonly known as Karanj oil in Ayurvedic and Siddha traditional systems of medicine, is reported for the treatment of various skin infections and psoriasis. Several phytopharmacological investigations have proved the medicinal potential of furanoflavonoids in the skin and other disorders. Not only furanoflavonoids but several other important phenolic constituents such as chalcones, dibenzoylmethanes, aurones, isoflavones, flavanone dihydroflavonol, flavans, pterocarpans, rotenoids, coumarins, coumestans, stilbenoids and peltygynoids and their glycosides have been reported for different biological activities including antihyperglycemic, anti-inflammatory, anticancer, insecticidal, anti-alzheimer's, gastro protective, antifungal, antibacterial, etc. In the present review, the phytochemistry and pharmacological activities of the genera Pongamia and Derris have been summarized.

Evaluation of Antimalarial Activity of 80% Methanolic Root Extract of Dorstenia barnimiana Against Plasmodium berghei-Infected Mice

BACKGROUND

Due to resistance of parasites, costs, and safety issues with currently available drugs, there is a need to discover new antimalarials. Medicinal plants are one of the most important sources of new drugs. The purpose of this study was to evaluate the antimalarial activity of a methanolic root extract of Dorstenia barnimiana in Swiss albino mice infected with Plasmodium berghei.

METHODS

Four-day suppressive, curative, and prophylactic tests were performed on mice infected with P. berghei to evaluate the antimalarial activity of a methanolic root extract of the plant. Parasitemia suppression, survival time, body-weight change, rectal temperature change, and packed-cell volume were used to evaluate the activity of the extract. Data were analyzed using one-way ANOVA followed by Tukey's post hoc test for comparisons between and within groups, with P<0.05 considered statistically significant.

RESULTS

The D. barnimiana root extract showed significant (P<0.01) parasitemia-suppressive activities in all models compared to the negative control. The extract increased mean survival time and prevented weight loss, reduction in temperature, and anemia significantly in all tested doses in 4-day suppressive and curative tests.

CONCLUSION

Based on these findings, D. barnimiana root has promising antimalarial activity and can considered a potential source to develop new agents.

Evaluation of the Antimalarial Activity of the Leaf Latex of Aloe weloensis (Aloaceae) against Plasmodium Parasites

Background

The lack of available vaccines and the emerging resistance to antimalarial drugs have provided the necessity to find noble antimalarial plant-based medicines. The leaf latex Aloe weloensis has been used in folk medicine against malarial and other human ailments in Ethiopia. Hence, the present study aimed to investigate the antimalarial activity of the leaf latex of A. weloensis against Plasmodium parasites.

Materials and Methods

The prophylactic and curative models were employed to determine the in vivo antimalarial activity of the leaf latex A. weloensis against P. berghei infected mice, and the antioxidant activity of the latex was assessed using diphenyl-1-picrylhydrazine (DPPH) assay. Female mice were recruited for toxicity study, and the leaf latex was administered to fasted mice at a dose of 5000 mg/kg. The mice were kept under continuous observation for fourteen days for any signs of overt toxicity.

Results

The leaf latex of A. weloensis was safe up to 5000 mg/kg, and the latex endowed free radical inhibition activity (IC₅₀ = 10.25 μg/ml). The latex of A. weloensis leaf demonstrated the inhibitory activity against the 3D7 strain of P. falciparum (IC₅₀ = 9.14 μg/ml). The prophylactic and curative effect of the latex was found to be dose-dependent. The mice's parasitemia level was significantly (p < 0.001) reduced at all tested doses of the leaf latex compared to negative control in the curative test. Parasitemia reduction was significant (200 mg/kg, p < 0.01, and 400 and 600 mg/kg, p < 0.001) in the prophylactic test compared to the control. In addition, the leaf latex significantly (p < 0.01) improved mean survival time, packed cell volume, rectal temperature, and bodyweight of P. berghei infected mice.

Conclusion

The leaf latex of Aloe weloensis was endowed with the antimalarial activity at various doses, corroborating the plant's claimed traditional use.

Capsicum frutescens and Citrus limon: a new take on therapy against experimental trichinellosis

Trichinellosis is a zoonotic disease that endangers human health and can lead to death. Restricted absorption and poor results of conventional therapies demand new effective natural remedies to treat both enteral and parenteral trichinellosis. This study assessed the antiparasitic and anti-inflammatory effects of Citrus limon and Capsicum frutescens on murine trichinellosis and compared them with those of albendazole and prednisolone, which are conventionally used to treat trichinellosis. Overall, 50 Swiss albino male mice were divided into five groups, with ten mice in each group: negative control, positive control, albendazole combined with prednisolone, C. limon, and C. frutescens. Mice were sacrificed 7 and 35 days after infection, for intestinal and muscular phase analyses. Drug efficacies were parasitologically, biochemically, histopathologically and ultrastructurally assessed. Our results demonstrated the efficacy of C. frutescens and C. limon extracts as antiparasitic agents, showing a substantial decrease in adult and larval counts. Moreover, both extracts had the ability to decrease serum tumour necrosis factor-α levels during the intestinal and muscular phases. In addition to the improved histopathological changes in the small intestine and muscles, the destructive effects on adults and larvae were ultrastructurally evident on transmission electron microscopy. In conclusion, C. frutescens and C. limon extracts are promising remedies for the treatment of experimental trichinellosis, particularly, the C. frutescens extract.

Design, synthesis, and antibacterial evaluation of new quinoline-1,3,4-oxadiazole and quinoline-1,2,4-triazole hybrids as potential inhibitors of DNA gyrase and topoisomerase IV

DNA gyrase and topoisomerase IV (topo IV) inhibitors are among the most interesting antibacterial drug classes without antibacterial pipeline representative. Twenty-four new quinoline-1,3,4-oxadiazole and quinoline-1,2,4-triazole hybrids were developed and tested against DNA gyrase and topoisomerase IV from Escherichia coli and Staphylococcus aureus. The most potent compounds 4c, 4e, 4f, and 5e displayed an IC₅₀ of 34, 26, 32, and 90 nM against E. coli DNA gyrase, respectively (novobiocin, IC₅₀ = 170 nM). The activities of 4c, 4e, 4f, and 5e on DNA gyrase from S. aureus were weaker than those on E. coli gyrase. Compound 4e showed IC₅₀ values (0.47 µM and 0.92 µM) against E. coli topo IV and S. aureus topo IV, respectively in comparison to novobiocin (IC₅₀ = 11, 27 µM, respectively). Antibacterial activity against Gram-positive and Gram-negative bacterial strains has been studied. Some compounds have demonstrated superior antibacterial activity to ciprofloxacin against some of the bacterial strain studied. The most active compounds in this study showed no cytotoxic effect with cell viability>86%. Finally, a molecular docking analysis was performed to investigate the binding mode and interactions of the most active compounds to the active site of DNA gyrase and topoisomerase IV (topo IV) enzymes.

Novel Benzenesulfonate Scaffolds with a High Anticancer Activity and G2/M Cell Cycle Arrest

Sulfonates, unlike their derivatives, sulphonamides, have rarely been investigated for their anticancer activity. Unlike the well-known sulphonamides, esters are mainly used as convenient intermediates in a synthesis. Here, we present the first in-depth investigation of quinazoline sulfonates. A small series of derivatives were synthesized and tested for their anticancer activity. Based on their structural similarity, these compounds resemble tyrosine kinase inhibitors and the p53 reactivator CP-31398. Their biological activity profile, however, was more related to sulphonamides because there was a strong cell cycle arrest in the G2/M phase. Further investigation revealed a multitargeted mechanism of the action that corresponded to the p53 protein status in the cell. Although the compounds expressed a high submicromolar activity against leukemia and colon cancers, pancreatic cancer and glioblastoma were also susceptible. Apoptosis and autophagy were confirmed as the cell death modes that corresponded with the inhibition of metabolic activity and the activation of the p53-dependent and p53-independent pathways. Namely, there was a strong activation of the p62 protein and GADD44. Other proteins such as cdc2 were also expressed at a higher level. Moreover, the classical caspase-dependent pathway in leukemia was observed at a lower concentration, which again confirmed a multitargeted mechanism. It can therefore be concluded that the sulfonates of quinazolines can be regarded as promising scaffolds for developing anticancer agents.

Cheminformatics techniques in antimalarial drug discovery and development from natural products 2: Molecular scaffold and machine learning approaches

A large number of natural products, especially those used in ethnomedicine of malaria, have shown varying in-vitro antiplasmodial activities. Cheminformatics involves the organization, integration, curation, standardization, simulation, mining and transformation of pharmacology data (compounds and bioactivity) into knowledge that can drive rational and viable drug development decisions. This chapter will review the application of two cheminformatics techniques (including molecular scaffold analysis and bioactivity predictive modeling via Machine learning) to natural products with in-vitro and in-vivo antiplasmodial activities in order to facilitate their development into antimalarial drug candidates and design of new potential antimalarial compounds.

Xylopic acid-amodiaquine and xylopic acid-artesunate combinations are effective in managing malaria in Plasmodium berghei-infected mice

Background

Evidence of Plasmodium resistance to some of the current anti-malarial agents makes it imperative to search for newer and effective drugs to combat malaria. Therefore, this study evaluated whether the co-administrations of xylopic acid-amodiaquine and xylopic acid-artesunate combinations will produce a synergistic anti-malarial effect.

Methods

Antiplasmodial effect of xylopic acid (XA: 3, 10, 30, 100, 150 mg kg⁻¹), artesunate (ART: 1, 2, 4, 8, 16 mg kg⁻¹), and amodiaquine (AQ: 1.25, 2.5, 5, 10, 20 mg kg⁻¹) were evaluated in Plasmodium berghei (strain ANKA)-infected mice to determine respective ED₅₀s. Artemether/lumefantrine was used as the positive control. XA/ART and XA/AQ were subsequently administered in a fixed-dose combination of their ED₅₀s (1:1) and the combination fractions of their ED₅₀s (1/2, 1/4, 1/8, 1/16, and 1/32) to determine the experimental ED₅₀s (Z_exp). An isobologram was constructed to determine the nature of the interaction between XA/ART, and XA/AQ combinations by comparing Z_exp with the theoretical ED₅₀ (Z_add). Bodyweight and 30-day survival post-treatment were additionally recorded.

Results

ED₅₀s for XA, ART, and AQ were 9.0 ± 3.2, 1.61 ± 0.6, and 3.1 ± 0.8 mg kg⁻¹, respectively. The Z_add, Z_exp, and interaction index for XA/ART co-administration was 5.3 ± 2.61, 1.98 ± 0.25, and 0.37, respectively while that of XA/AQ were 6.05 ± 2.0, 1.69 ± 0.42, and 0.28, respectively. The Z_exp for both combination therapies lay significantly (p < 0.001) below the additive isoboles showing XA acts synergistically with both ART and AQ in clearing the parasites. High doses of XA/ART combination significantly (p < 0.05) increased the survival days of infected mice with a mean hazard ratio of 0.40 while all the XA/AQ combination doses showed a significant (p < 0.05) increase in the survival days of infected mice with a mean hazard ratio of 0.27 similar to AL. Both XA/ART and XA/AQ combined treatments significantly (p < 0.05) reduced weight loss.

Conclusion

Xylopic acid co-administration with either artesunate or amodiaquine produces a synergistic anti-plasmodial effect in mice infected with P. berghei.

Antimalarial Activity of Nigella sativa L. Seed Extracts and Selection of Resistance in Plasmodium berghei ANKA in a Mouse Model

Background

Chemotherapy plays a crucial role in malaria control. However, the main obstacle to treatment has been the rise of parasite resistance to most antimalarial drugs. Artemisinin-based combination therapies (ACTs) remain the most effective antimalarial medicines available today. However, malaria parasite tolerance to ACTs is now increasingly prevalent especially in Southeast Asia presenting the danger of the spread of ACTs resistance to other parts of the world. Consequently, this creates the need for alternative effective antimalarials. Therefore, this study sought out to determine antimalarial potential, safety, and resistance development of the extracts in a mouse model.

Method

Methanolic and ethyl acetate extracts were obtained by solvent extraction. The extracts were assayed for acute toxicity in vivo. Additionally, the two extracts were evaluated for antimalarial activity in vivo against Plasmodium berghei ANKA strain by the 4-day suppressive test at 500, 250, and 125 mg/kg/day. Packed cell volume was evaluated to determine anemia manifestation. Finally, continuous drug pressure experiment at 500 mg/kg and DNA amplification via PCR were conducted. The amplicons underwent through Sanger sequencing.

Results

There was no toxicity realized in the animals at 2000 mg/kg. Importantly, high parasitemia suppression of 75.52% and 75.30% using a dose of 500 mg/kg of methanolic and ethyl acetate extracts, respectively, was noted. The extracts were able to reverse packed cell volume reduction. Nigella sativa-resistant phenotype was selected as delayed parasite clearance. However, there was no change in the nucleotide sequences of PbMDR1 and PbCRT genes.

Conclusion

The results provide room for future exploitation of the plant as an antimalarial.

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.

Antiplasmodial and antileishmanial flavonoids from Mundulea sericea

Five known compounds (1-5) were isolated from the extract of Mundulea sericea leaves. Similar investigation of the roots of this plant afforded an additional three known compounds (6-8). The structures were elucidated using NMR spectroscopic and mass spectrometric analyses. The absolute configuration of 1 was established using ECD spectroscopy. In an antiplasmodial activity assay, compound 1 showed good activity with an IC₅₀ of 2.0 μM against chloroquine-resistant W2, and 6.6 μM against the chloroquine-sensitive 3D7 strains of Plasmodium falciparum. Some of the compounds were also tested for antileishmanial activity. Dehydrolupinifolinol (2) and sericetin (5) were active against drug-sensitive Leishmania donovani (MHOM/IN/83/AG83) with IC₅₀ values of 9.0 and 5.0 μM, respectively. In a cytotoxicity assay, lupinifolin (3) showed significant activity on BEAS-2B (IC₅₀ 4.9 μM) and HePG2 (IC₅₀ 10.8 μM) human cell lines. All the other compounds showed low cytotoxicity (IC₅₀ > 30 μM) against human lung adenocarcinoma cells (A549), human liver cancer cells (HepG2), lung/bronchus cells (epithelial virus transformed) (BEAS-2B) and immortal human hepatocytes (LO2).

Total Syntheses of Prenylated Isoflavones from Erythrina sacleuxii and Their Antibacterial Activity: 5-Deoxy-3'-prenylbiochanin A and Erysubin F

The prenylated isoflavones 5-deoxyprenylbiochanin A (7-hydroxy-4'-methoxy-3'-prenylisoflavone) and erysubin F (7,4'-dihydroxy-8,3'-diprenylisoflavone) were synthesized for the first time, starting from mono- or di-O-allylated chalcones, and the structure of 5-deoxy-3'-prenylbiochanin A was corroborated by single-crystal X-ray diffraction analysis. Flavanones are key intermediates in the synthesis. Their reaction with hypervalent iodine reagents affords isoflavones via a 2,3-oxidative rearrangement and the corresponding flavone isomers via 2,3-dehydrogenation. This enabled a synthesis of 7,4'-dihydroxy-8,3'-diprenylflavone, a non-natural regioisomer of erysubin F. Erysubin F (8), 7,4'-dihydroxy-8,3'-diprenylflavone (27), and 5-deoxy-3'-prenylbiochanin A (7) were tested against three bacterial strains and one fungal pathogen. All three compounds are inactive against Salmonella enterica subsp. enterica (NCTC 13349), Escherichia coli (ATCC 25922), and Candida albicans (ATCC 90028), with MIC values greater than 80.0 μM. The diprenylated natural product erysubin F (8) and its flavone isomer 7,4'-dihydroxy-8,3'-diprenylflavone (27) show in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA, ATCC 43300) at MIC values of 15.4 and 20.5 μM, respectively. In contrast, the monoprenylated 5-deoxy-3'-prenylbiochanin A (7) is inactive against this MRSA strain.

Indole: The After Next Scaffold of Antiplasmodial Agents?

Malaria remains a global public health problem due to the uphill fight against the causative Plasmodium parasites that are relentless in developing resistance. Indole-based antiplasmodial compounds are endowed with multiple modes of action, of which inhibition of hemozoin formation is the major mechanism of action reported for compounds such as cryptolepine, flinderoles, and isosungucine. Indole-based compounds exert their potent activity against chloroquine-resistant Plasmodium strains by inhibiting hemozoin formation in a mode of action different from that of chloroquine or through a novel mechanism of action. For example, dysregulating the sodium and osmotic homeostasis of Plasmodium through inhibition of PfATP4 is the novel mechanism of cipargamin. The potential of developing multi-targeted compounds through molecular hybridization ensures the existence of indole-based compounds in the antimalarial pipeline.