Antimalarial potential of Kerala Ayurvedic Water.

BACKGROUND OBJECTIVES: The persistent threat of drug resistant malaria demands new cures. Low prevalence of malaria in the Indian state of Kerala compared with other proximal states made us explore if there is any traditional practice in Kerala which may confer protection against malaria. In this context, our attention was drawn to 'Pathimugam' i.e., Ceasalpinia sappan whose heartwood is used to prepare a red aqueous extract which is a uniquely popular drink in Kerala. METHODS: Aqueous and methanolic extracts of various organs of C. sappan were prepared and tested against Plasmodium falciparum grown in vitro culture using SYBR Green-I assay. The cytotoxicity of active extracts/fractions was studied using mammalian HeLa cell line. in vivo efficacy was determined using P. berghei ANKA infected mice. RESULTS: The highest antiplasmodial activities in the alcoholic and aqueous extracts were observed in leaf methanolic extract (IC50 2 µg/ml) and heartwood aqueous extract (IC50 12.5 µg/ml). Ceasalpinia sappan extracts were equipotent against both chloroquine-sensitive Pf3D7 and resistant PfINDO strains and showed suppression of percentage parasitemia in P. berghei infected mice. Activity- guided chromatographic fractionation of aqueous wood extract led to the fortification of antiplasmodial activity (IC50 5 µg/ml). INTERPRETATION CONCLUSION: Our results establish the antiplasmodial potential of C. sappan and suggest that its regular use might have prophylactic or curative actions that may assist in keeping check on malaria in the Indian state of Kerala.

Novel quinolinepiperazinyl-aryltetrazoles targeting the blood stage of Plasmodium falciparum.

The emergence of drug resistance against the frontline antimalarials is a major challenge in the treatment of malaria. In view of emerging reports on drug-resistant strains of Plasmodium against artemisinin combination therapy, a dire need is felt for the discovery of novel compounds acting against novel targets in the parasite. In this study, we identified a novel series of quinolinepiperazinyl-aryltetrazoles (QPTs) targeting the blood stage of Plasmodium. In vitro anti-plasmodial activity screening revealed that most of the compounds showed IC50 < 10 µM against chloroquine-resistant PfINDO strain, with the most promising lead compounds 66 and 75 showing IC50 values of 2.25 and 1.79 µM, respectively. Further, compounds 64-66, 68, 75-77 and 84 were found to be selective (selectivity index >50) in their action against Pf over a mammalian cell line, with compounds 66 and 75 offering the highest selectivity indexes of 178 and 223, respectively. Explorations into the action of lead compounds 66 and 75 revealed their selective cidal activity towards trophozoites and schizonts. In a ring-stage survival assay, 75 showed cidal activity against the early rings of artemisinin-resistant PfCam3.1R539T. Further, 66 and 75 in combination with artemisinin and pyrimethamine showed additive to weak synergistic interactions. Of these two in vitro lead molecules, only 66 restricted rise in the percentage of parasitemia to about 10% in P. berghei-infected mice with a median survival time of 28 days as compared to the untreated control, which showed the percentage of parasitemia >30%, and a median survival of 20 days. Promising antimalarial activity, high selectivity, and additive interaction with artemisinin and pyrimethamine indicate the potential of these compounds to be further optimized chemically as future drug candidates against malaria.

Identification of Novel, Potent, and Selective Compounds against Malaria Using Glideosomal-Associated Protein 50 as a Drug Target.

Phylum apicomplexan consists of parasites, such as Plasmodium and Toxoplasma. These obligate intracellular parasites enter host cells via an energy-dependent process using specialized machinery, called the glideosome. In the present study, we used Plasmodium falciparum GAP50, a glideosome-associated protein, as a target to screen 951 different compounds from diverse chemical libraries. Using different screening methods, eight compounds (Hayatinine, Curine, MMV689758 (Bedaquiline), MMV1634402 (Brilacidin), and MMV688271, MMV782353, MMV642550, and USINB4-124-8) were identified, which showed promising binding affinity (KD < 75 µM), along with submicromolar range antiparasitic efficacy and selectivity index > 100 fold for malaria parasite. These eight compounds were effective against Chloroquine-resistant PfINDO and Artemisinin-resistant PfCam3.1R359T strains. Studies on the effect of these compounds at asexual blood stages showed that these eight compounds act differently at different developmental stages, indicating the binding of these compounds to other Plasmodium proteins, in addition to PfGAP50. We further studied the effects of compounds (Bedaquiline and USINB4-124-8) in an in vivoPlasmodium berghei mouse model of malaria. Importantly, the oral delivery of Bedaquiline (50 mg/kg b. wt.) showed substantial suppression of parasitemia, and three out of seven mice were cured of the infection. Thus, our study provides new scaffolds for the development of antimalarials that can act at multiple Plasmodium lifecycle stages.

Innate functions of natural products: A promising path for the identification of novel therapeutics.

In the course of evolution, living organisms have become well equipped with diverse natural products that serve important functions, including defence from biotic and abiotic stress, growth regulation, reproduction, metabolism, and epigenetic regulation. It seems to be the organism's ecological niche that influences the natural product's structural and functional diversity. Indeed, natural products constitute the nuts and bolts of molecular co-evolution and ecological relationships among different life forms. Since natural products in the form of specialized secondary metabolites exhibit biological functions via interactions with specific target proteins, they can provide a simultaneous glimpse of both new therapeutics and therapeutic targets in humans as well. In this review, we have discussed the innate role of natural products in the ecosystem and how this intrinsic role provides a futuristic opportunity to identify new drugs and therapeutic targets rapidly.

Marmesin isolated from Celtis durandii Engl. root bioactive fraction inhibits ß-hematin formation and contributes to antiplasmodial activity.

ETHNOPHARMACOLOGICAL RELEVANCE: Malaria is a leading cause of death in many developing countries, especially in sub-Saharan Africa. Nigeria is endowed with an abundance of medicinal plants, many of which are used to treat malaria. Celtis durandii Engl. is one such plant used as a traditional antimalarial remedy in southeast Nigeria. However, its antiplasmodial potential is poorly explored. AIM OF THE STUDY: The study aimed at identifying the antiplasmodial components of C. durandii root extract through antiplasmodial activity-guided fractionation. MATERIALS AND METHODS: Dichloromethane/methanol mixture extract (1:1 v/v) of C. durandii root was prepared and partitioned against water to obtain the organic phase, which was further separated by column chromatography into nine (C1 - C9) fractions. The antiplasmodial activity was evaluated by in vitro screening of the different fractions against drug-sensitive and drug-resistant Plasmodium falciparum strains. Further purification of the active column fractions resulted in a potent anti-Plasmodial compound that was subsequently investigated for its effect on ß-hematin formation. Additionally, the isolated compound was characterized and identified as marmesin using mass spectrometry and nuclear magnetic resonance spectroscopy. RESULTS: Celtis durandii root extract exhibited promising antiplasmodial activity {IC50 (µg/ml) 5.92, 6.04, and 6.92} against PfW2mef, PfINDO, and Pf3D7 respectively. Pooled fractions with good antiplasmodial activity {IC50 (µg/ml) Pf3D7: 3.99; PfINDO: 2.24} and selectivity for the parasites (SI: 21) yielded a compound that was fourteen-fold potent in antiplasmodial activity against Pf3D7(IC50: 0.28 µg/ml). It also inhibited ß-hematin formation with an IC50 = 150 µM. Further studies using spectral data, literature, and chemical databases identified the purified compound as marmesin. CONCLUSION: This work has demonstrated that Celtis durandii root extract has good antiplasmodial activity against drug-sensitive and drug-resistant P. falciparum. The inhibition of ß-hematin formation by marmesin accounts in part for this activity.

Antiplasmodial activity of the bulbs of Fritillaria cirrhosa D.Don (Syn: Fritillaria roylei Hook.): UPLC-IM-Q-TOF-MS/MS-based biochemometric approach for the identification of marker compounds.

ETHNOPHARMACOLOGICAL RELEVANCE: Fritillaria cirrhosa D.Don (Syn: Fritillaria roylei Hook.) (Hindi name: Kshirakakoli) is a critically endangered Himalayan medicinal plant, well documented in Ayurveda for its therapeutic uses against various disorders such as jvara (fever), kasa (respiratory tract disease) etc. Its bulbs are also used as Szechuan-Pei-Mu for their antipyretic properties in the traditional Chinese medicine. However, despite its ethnomedicinal usage, the therapeutic use of F. cirrhosa bulbs for jvara (fever) related conditions such as malaria has remained unexplored. Hence in the context of increasing global concerns about drug-resistant malaria, it is important to investigate the antiplasmodial activity of F. cirrhosa bulbs for novel antimalarial agents. AIM OF THE STUDY: To investigate the antiplasmodial effects of the extracts/fractions of F. cirrhosa bulbs by the biochemometric approach and to rationalize its ethnopharmacological usage for jvara (fever) related conditions such as malaria. MATERIAL AND METHODS: This study involves the UHPLC-MS-based plant material selection, preparation, quantification, and assessment of F. cirrhosa bulb extracts against CQ-sensitive Pf 3D7 & CQ-resistant Pf INDO strains. Further, UPLC-IM-Q-TOF-MS-based biochemometric approach has been applied for the identification of marker compounds responsible for the observed antiplasmodial effects. The identified marker compounds were also assessed for their in silico ADMET properties and binding efficacy with the drug transporter Pf CRT. RESULTS: Different F. cirrhosa bulb extracts/fractions showed promising antiplasmodial activity with IC50 values 2.71-19.77 µg/mL for CQ-resistant Pf INDO strain and 1.76-21.52 µg/mL for CQ-sensitive Pf 3D7 strain. UPLC-IM-Q-TOF-MS/MS-based biochemometric analysis revealed four marker compounds i.e., peimine (m/z 432.3448), peimisine (m/z 428.3504), puqiedinone (m/z 414.3379), and puqiedine (m/z 416.3509) responsible for the observed antiplasmodial activity. The identified marker compounds showed excellent binding efficacy with Pf CRT and suitable drug-like properties in silico. CONCLUSIONS: The study demonstrated promising antiplasmodial activity of the chloroform and alkaloid enriched fractions of F. cirrhosa bulbs and further identified the four marker compounds responsible for the promising antiplasmodial activity. These marker compounds i.e., peimine, peimisine, puqiedinone and puqiedine were identified by the biochemometric analysis as the putative antiplasmodial constituents of the F. cirrhosa bulbs. Further, in silico studies indicated the good binding affinity of the marker compounds with Pf CRT along with suitable ADMET properties. Overall, the study elucidates the antiplasmodial activity of F. cirrhosa bulbs from the western Himalayan region and provides nascent scientific evidence for their ethnopharmacological usage in jvara (fever) related conditions such as malaria.

Antiplasmodial and antimalarial evaluation of a Nigerian hepta-herbal Agbo-iba decoction: Identification of magic bullets and possible facilitators of drug action.

ETHNOPHARMACOLOGICAL RELEVANCE: Malaria remains one of the most important pathogenic infectious diseases. Although Africa suffers the greatest brunt, a sizeable proportion of her population still relies on herbal medicines for reasons of cost as well as the belief etched in the minds of consumers that herbal medicines are safer and more efficacious than Modern medicines. Agbo-iba; a concoction of two or more than two plants is commonly used for the management of malaria in Nigeria. AIM OF THE STUDY: This study assessed the safety and efficacy of a hepta-herbal Agbo-iba (HHA) antimalarial decoction used for the management of malaria in Benin city, Nigeria. MATERIALS AND METHODS: Assessment was done against malaria parasite in culture as well as in vivo in pre-clinical murine model of malaria. RESULTS: HHA (IC50Pf3D7 50 µg/ml) was moderately potent and only one of its constituent plants Annickia affinis (IC50Pf3D7 1.49 µg/ml) was far more potent, while all others were moderately active to inactive against the parasite in vitro. HHA showed good selectivity in vitro and was safe at 2 g/kg in mice. However, at 100 mg/kg oral dose, while HHA suppressed parasite growth by 56.76%, the suppression caused by A.affinis was only 32.46% in mice malaria suggesting the existence of synergistic partner(s) in the herbal formula. LCMS revealed the presence of quaternary protoberberine alkaloids (QPAs) in A.affinis and HHA. CONCLUSIONS: Although QPAs have strong in vitro antiplasmodial activity, their in vivo antimalarial activity is undermined by being substrates of Permeability glycoprotein (Pgp) efflux pump. Our study suggests that inhibitor(s) of Pgp in HHA could improve the bioavailability of QPAs in mice fed the herbal combo. Further, molecules from other HHA constituent plants may also contribute to the better potency observed for the polyherbal in vivo. These possibilities were validated by the curative antimalarial study at 100 mg/kg, where A.affinis was inactive but the HHA suppressed parasite growth by 44.45%.

Antiplasmodial and Antimalarial Activity of 3,5-Diarylidenetetrahydro-2H-pyran-4(3H)-ones via Inhibition of Plasmodium falciparum Pyridoxal Synthase.

A series of 22 different 3,5-diarylidenetetrahydro-2H-pyran-4(3H)-ones (DATPs) were synthesized, characterized, and screened for their in vitro antiplasmodial activities against chloroquine (CQ)-sensitive Pf3D7, CQ-resistant PfINDO, and artemisinin-resistant PfMRA-1240 strains of Plasmodium falciparum. DATP 19 (3,5-bis(4-hydroxy-3,5-dimethoxybenzylidene)tetrahydro-2H-pyran-4(3H)-one) was found to be the most potent (IC50 1.07 µM) against PfMRA-1240, whereas 21 (3,5-bis(3,4,5-trimethoxybenzylidene)tetrahydro-2H-pyran-4(3H)-one) showed IC50 values of 1.72 and 1.44 µM against Pf3D7 and PfINDO, respectively. Resistance indices (RI) as low as 0.2 to 0.5 for 10 (3,5-bis(4-nitrobenzylidene)tetrahydro-2H-pyran-4(3H)-one) and 20 (3,5-bis(3-nitrobenzylidene)tetrahydro-2H-pyran-4(3H)-one), and <1 for most other DATPs reveals their greater potency against resistant strains than the sensitive one. The single-crystal XRD data for DATP 21 are reported. In silico support was obtained through docking studies. Killing all three strains within 4-8 h, these DATPs showed rapid kill kinetics toward the trophozoite stage. Furthermore, DATP 18 (3,5-bis(quinolin-4-ylmethylene)tetrahydro-2H-pyran-4(3H)-one) inhibited PfPdx1 enzyme activity with IC50 20.34 µM, which is about twofold lower than that (IC50 43 µM) for an already known inhibitor 4PEHz. At an oral dose of 300 mg/kg body weight, DATPs 19 and 21 were found to be nontoxic to mice, and at 100 mg/kg body weight, DATP 19 was found to suppress parasitaemia, which led to an increase in median survival time by three days relative to untreated control mice in a malaria curative study.

Assessment of antimalarial medicinal plants used in Nigerian ethnomedicine reveals antimalarial potential of Cucurbita pepo leaf extract.

Medicinal plants are often used to treat malaria in different parts of Nigeria and exploiting these can unravel new therapeutic leads. This study evaluated the antiplasmodial potential of selected plants used to treat malaria in Nsukka, Enugu state, Nigeria. Leaves of three different plants (Cucurbita pepo, Hibiscus rosa-sinensis and Pennisetum purpureum) were collected for screening and two extracts viz., 70%v/v ethanol and dichloromethane/methanol (1:1 v/v), were prepared for each. An acute toxicity test was done in mice and cytotoxicity was assessed using human hepatoma cell line (HUH). The extracts were screened against chloroquine-sensitive P. falciparum (Pf3D7) in vitro, and chloroquine-resistant P. berghei ANKA in vivo using a 4 day-suppressive test in mice. Cucurbita pepo ethanol extract was further tested for hemolytic effect on human erythrocytes and in established infection in mice. Parameters assessed were post-treatment parasitemia, hematological indices, organ (brain, kidney, liver, and spleen) weights, and survival. The extracts were non-cytotoxic up to a test dose of 100 µg/ml and 2000 mg/kg fed - mice did not show acute or delayed toxicity. Cucurbita pepo ethanol extract (CpE) displayed excellent in vitro antiplasmodial activity with IC50 of 3.05 µg/ml. At an oral dose of 500 mg/kg, mice were observed to display significant (p < 0.01) ∼51% suppression of parasitemia. The extract did not produce any significant hemolytic effect up to a test concentration of 1 mg/ml. In established infection, a dose of 300 mg/kg significantly (p < 0.01) protected mice from anemia caused by low hematocrit. The extract produced significant (p < 0.05) elevation in red blood cells and platelet counts, and an increase in hemoglobin was evident at 100 and 300 mg/kg. Further, CpE in a dose-dependent manner, reversed liver and spleen weight increase seen in untreated, infected mice. These findings show C. pepo as a potential candidate for further studies to identify its bioactive principle(s) and possible mechanism(s) of antimalarial action.

Antiplasmodial diterpenoid alkaloid from Aconitum heterophyllum Wall. ex Royle: Isolation, characterization, and UHPLC-DAD based quantification.

ETHNOPHARMACOLOGICAL RELEVANCE: Aconitum heterophyllum Wall. ex Royle is a traditionally important medicinal plant having numerous therapeutic actions as documented in Ayurveda. This plant is traditionally known for combating worm infestation, fever, respiratory tract disease, vomiting, diarrhoea, diabetes, skin disorders, anaemia, and joint disorders. Further, it has been used alone and in combination with other plants to prepare various anti-malarial formulations. However, there is no report on the assessment of its anti-plasmodial activity, and the metabolite(s) responsible for this activity. AIM OF THE STUDY: The main aim of this study was to conduct phytochemical investigation of A. heterophyllum roots for the preparation of extract, fractions, and isolation of pure molecules to identify active fractions/molecules responsible for the anti-plasmodial activity, and development of UHPLC-DAD based analytical method which can be used for the quantification of marker compounds in the extracts and fractions. MATERIALS AND METHODS: Hydroalcoholic extract (1:1 v/v) and fractions (n-hexane, chloroform, ethyl acetate, n-butanol, and water) were prepared from the dried powdered roots of A. heterophyllum. Fractions were further subjected to silica gel column chromatography to isolate pure specialized secondary metabolites from this plant. All extracts, fractions, and pure molecules were evaluated against the chloroquine resistant Pf INDO and chloroquine sensitive Pf3D7 strains in culture for calculating their IC50 values. UHPLC-DAD based analytical method was also developed for the first time for the quantification of marker compounds and quality assessment of this commercially important Himalayan medicinal plant. RESULTS: Phytochemical investigation of A. heterophyllum root led to the isolation of six specialized metabolites viz. 2-O-cinnamoyl hetisine (1), atisinium (2), 4-oxabicyclo [3.2.2] nona-1(7),5,8-triene (3), atisinium cinnamate (4), aconitic acid (5), and atisinium formate (6). Compound 1 is a new hetisine type diterpenoid alkaloid, compounds 4 and 6 are new counter ionic forms observed with atisinium ion, and compound 3 is being reported for the first time from this genus. Chloroform fraction was found to be the most active with IC50 (µg/mL) 1.01 (Pf INDO) and 1.32 (Pf3D7). The molecule 2-O-cinnamoyl hetisine (1), a new diterpenoid alkaloid isolated from chloroform fraction, showed promising antiplasmodial activities with IC50 (µM) 1.92 (Pf INDO) and 10.8 (Pf 3D7). The activity of chloroform fraction was further validated by the developed UHPLC-DAD based method as the quantity of 2-O-cinnamoyl hetisine (1) was higher in the chloroform fraction (≅200 mg/g) than in all other fractions (<7 mg/g). Atisinium (2) and 2-O-cinnamoyl hetisine (1) were found to be the main marker compounds of this plant based on quantity and antiplasmodial activity, respectively. CONCLUSION: This study provides the scientific rationale for the traditional use of this plant in treating malaria. Further, this study revealed that the anti-malarial potential of this plant might be due to the presence of diterpenoid alkaloids.

Specific sub fractions from Terminalia mantaly (H. Perrier) extracts potently inhibit Plasmodium falciparum rings, merozoite egress and invasion.

ETHNOPHARMACOLOGICAL RELEVANCE: Terminalia mantaly (H. Perrier) and Terminalia superba (Engl. & Diels) are sources of treatment for various diseases, including malaria and/or related symptoms in parts of Southwestern Cameroon. However, there is limited information on the extent of the antiplasmodial potential of their extracts. AIM OF THE STUDY: The present study was designed to investigate the antiplasmodial potential of chromatographic sub fractions (SFs) from promising fractions of Terminalia mantaly (Tm) [TmsbwChl, the chloroform fraction from water extract of Tm, IC50 (µg/mL) PfINDO: 0.56, Pf3D7: 1.12; SI > 357 (HEK/PfINDO) & 178 (HEK/Pf3D7)] and Terminalia superba (Ts) [TsrmEA, the ethyl acetate fraction from methanolic extract of Ts, IC50 (µg/mL) PfINDO: 1.82, Pf3D7: 1.65; SI > 109 (HEK/PfINDO) & 121 (HEK/Pf3D7)] obtained from previous studies. The SFs were tested against Plasmodium falciparum 3D7 (Pf3D7-chloroquine sensitive) and INDO (PfINDO-chloroquine resistant) strains in culture. Also, the phytochemical profile of potent SFs was determined and finally, the inhibition of the asexual blood stages of Plasmodium falciparum by the SFs with the highest promise was assessed. MATERIAL AND METHODS: Selected SFs were submitted to a second bio-guided fractionation using silica gel column chromatography. The partial phytochemical composition of potent antiplasmodial SFs was determined using gas chromatography coupled to mass spectrometry (GC-MS). The SYBR Green I-based fluorescence microtiter plate assay was used to monitor the growth of Plasmodium falciparum parasites in culture in the presence or absence of extracts. Microscopy and flow cytometry counting was used to assess the Plasmodium falciparum stage-specific inhibition and post-drug exposure growth suppression by highly potent extracts. RESULTS: Twenty-one of the 39 SFs afforded from TmsbwChl showed activity (IC50: 0.29-4.74 µg/mL) against both Pf3D7 and PfINDO strains. Of note, eight SFs namely, Tm25, Tm28-30, Tm34-36 and Tm38, exerted highly potent antiplasmodial activity (IC50 < 1 µg/mL) with IC50PfINDO: 0.41-0.84 µg/mL and IC50Pf3D7: 0.29-0.68 µg/mL. They also displayed very high selectivity (50 < SIPfINDO, SIPf3D7 > 344) on the two Plasmodial strains. On the other hand, 7 SFs (SFs Ts03, Ts04, Ts06, Ts09, Ts10, Ts12 and Ts13) from TsrmEA showed promising inhibitory potential against both parasite strains (IC50: 2.01-5.14 µg/mL). Sub fraction Tm36 (IC50PfINDO: 0.41 µg/mL, SIPfINDO > 243; IC50Pf3D7: 0.29 µg/mL, SIPf3D7 > 344) showed the highest promise. The GC-MS analysis of the 8 selected SFs led to the identification of 99 phytometabolites, with D-limonene (2), benzaldehyde (12), carvone (13), caryophyllene (35), hexadecanoic acid, methyl ester (74) and 9-octadecenoic acid, methyl ester (82) being the main constituents. Sub fractions Tm28, Tm29, Tm30, Tm36 and Tm38 inhibited all the three intraerythrocytic stages of P. falciparum, with strong potency against ring stage development, merozoite egress and invasion processes. CONCLUSIONS: This study has identified highly potent antiplasmodial SFs from Terminalia mantaly with significant activity on the intraerythrocytic development of Plasmodium falciparum. These SFs qualify as promising sources of novel antiplasmodial lead compounds. Further purification and characterization studies are expected to unravel molecular targets in rings and merozoites.

Protecting future antimalarials from the trap of resistance: Lessons from artemisinin-based combination therapy (ACT) failures.

Having faced increased clinical treatment failures with dihydroartemisinin-piperaquine (DHA-PPQ), Cambodia swapped the first line artemisinin-based combination therapy (ACT) from DHA-PPQ to artesunate-mefloquine given that parasites resistant to piperaquine are susceptible to mefloquine. However, triple mutants have now emerged, suggesting that drug rotations may not be adequate to keep resistance at bay. There is, therefore, an urgent need for alternative treatment strategies to tackle resistance and prevent its spread. A proper understanding of all contributors to artemisinin resistance may help us identify novel strategies to keep artemisinins effective until new drugs become available for their replacement. This review highlights the role of the key players in artemisinin resistance, the current strategies to deal with it and suggests ways of protecting future antimalarial drugs from bowing to resistance as their predecessors did.

Novel halogenated arylvinyl-1,2,4 trioxanes as potent antiplasmodial as well as anticancer agents: Synthesis, bioevaluation, structure-activity relationship and in-silico studies.

Herein, we have synthesized a series of lipophilic, halogenated-arylvinyl-1,2,4-trioxanes 8a-g (28 compounds) and assessed for their in vitro anti-plasmodial activity in Plasmodium falciparum culture using SYBRgreen-I fluorescence assay against chloroquine-resistant Pf INDO and artemisinin-resistant Pf Cam 3.1R539T (MRA-1240) strains. Alongside, the cell cytotoxic potential of 8a-g has also been determined against the HEK293 cell line in vitro. Out of twenty-eight halogenated-arylvinyl-1,2,4-trioxanes; ten analogues (8a2, 8a4, 8b2, 8b4, 8d4, 8e1, 8e2, 8e4,8f2, and 8g4) have shown potent in vitro antiplasmodial activity with IC50 < 27 nM (IC50 range = 4.48-26.58 nM). Also, the selectivity index (SI) for these ten analogues were found in the range of 72.00-3972.50 which indicates their selective potential towards Plasmodium cells. Results of the cell cycle stage specificity with two of the most potent compounds 8a4 {(IC50 = 4.48 nM; SI = 3972.50) more potent than chloroquine (IC50 = 546 nM; SI = 36.64) and artesunate (IC50 = 6.6 nM; SI = 4333.33)} and 8e2 (IC50 = 9.69 nM; SI = 1348) against Pf INDO indicated all three stages to be the target of the action of 8e2 while only rings and trophozoites appeared to be targeted by 8a4. Ring stage survival assay against artemisinin-resistant Pf Cam 3.1R539T indicated that 8a4 may be well suited to replace artemisinin from current ACTs which are experiencing in vivo delayed parasite clearance. With intraperitoneal (i.p.) and oral (p.o.) route at the dose of 50 mg/kg/day × 4 days; 8a4 has also shown 100% suppression of parasitemia in P. berghei ANKA infected Balb C mice. Further, the in vitro anticancer activity of 8a-g performed against human lung (A549) and liver (HepG2) cancer cell lines as also against immortalized normal lung (BEAS-2B) and liver (LO2) cell lines has revealed that most of the derivatives are endowed also with promising anticancer activity (IC50 = 0.69-15 µM; SI = 1.02-20.61) in comparison with standard drugs such as chloroquine (IC50 = 100 µM; SI = 0.03), artemisinin (IC50 = 100 µM), and artesunic acid (IC50 = 9.85 µM; SI = 0.76), respectively. All the derivatives have shown moderate anticancer activity against liver (HepG2) cancer cell lines. Arylvinyl-1,2,4-trioxanes 8f2 (IC50 = 0.69 µM; SI = 16.66), the most active compound of the series, has shown ∼145 fold more cytotoxic potential with higher selectivity in comparison to reference drugs chloroquine (IC50 = 100 µM; SI = 0.03) and artemisinin (IC50 = 100 µM), respectively against the lung (A549) cancer cell line. Finally, the in-silico docking studies of the potent halogenated 1,2,4-trioxanes along with reference drug molecules against epidermal growth factor receptor (EGFR; PDB ID: 1M17) have demonstrated the strong virtual interaction.

Specialized antiplasmodial secondary metabolites from Aspergillus niger 58, an endophytic fungus from Terminalia catappa.

ETHNOPHARMACOLOGICAL RELEVANCE: Terminalia catappa L. (West Indian-Almond) is a medicinal plant used in traditional medicine for the treatment of infectious diseases. Moreover, various organic extracts prepared from this plant have been reported to exhibit antiplasmodial activity. AIM OF THE STUDY: The need for new antimalarials is still an urgency driven by the alarmingly high burden of malaria in endemic regions, with multitude of people dying annually. We have previously identified an endophytic fungus Aspergillus niger 58 harboured by T. catappa as having promising specialized secondary metabolites against the malaria parasites. In the present study, we report the antiplasmodial activity-guided chromatographic isolation of some metabolites secreted by this endophytic fungus. MATERIALS AND METHODS: The SYBR Green I-based fluorescence microtiter plate assay was used to monitor the growth of Plasmodium falciparum parasites in culture in the presence and absence of inhibitors and results were validated by microscopic analysis of Giemsa-stained culture smears. Giemsa-stain microscopy was also used to study the cell cycle stage-specific action of selected fractions. RESULTS: The results revealed that the multidimensional purification of the crude extract (IC50: 4.03 µg/mL) provided RPHPLC F17 (IC50: 0.09 µg/mL) and RPHPLC F18 (IC50: 0.1 µg/mL) with activity against P. falciparum 3D7 (Pf3D7) strain. Moreover, both fractions at IC99 (0.5 µg/mL) exhibited multi-stages action by targeting all the three stages of the life cycle of blood-stage Pf3D7. Two compounds, flavasperone (1) and aurasperone A (2) were isolated, of which aurasperone A exhibited good potency against Pf3D7 (IC50: 4.17 µM) and P. falciparum INDO (PfINDO) (IC50: 3.08 µM). CONCLUSION: Our study adds credence to the notion that endophytic extracts are potential storehouses for potent specialized secondary metabolites that can be harnessed to fight the malaria parasite and reduce the burden of this disease worldwide. An endophyte that can be cultured in laboratory with ability to secrete promising metabolites of medicinal value holds the promise of conserving Nature from the threat of annihilation of flora for medicinal purposes.

Protecting future antimalarials from the trap of resistance:Lessons from artemisinin-based combination therapy(ACT)failures / 药物分析学报

Having faced increased clinical treatment failures with dihydroartemisinin-piperaquine(DHA-PPQ),Cambodia swapped the first line artemisinin-based combination therapy(ACT)from DHA-PPQ to artesunate-mefloquine given that parasites resistant to piperaquine are susceptible to mefloquine.However,triple mutants have now emerged,suggesting that drug rotations may not be adequate to keep resistance at bay.There is,therefore,an urgent need for alternative treatment strategies to tackle resistance and prevent its spread.A proper understanding of all contributors to artemisinin resistance may help us identify novel strategies to keep artemisinins effective until new drugs become available for their replacement.This review highlights the role of the key players in artemisinin resistance,the current strategies to deal with it and suggests ways of protecting future antimalarial drugs from bowing to resistance as their predecessors did.

A conversation between hyphenated spectroscopic techniques and phytometabolites from medicinal plants.

Medicinal plant metabolomics has emerged as a goldmine for the natural product chemists. It provides a pool of bioactive phytoconstituents leading to accelerated novel discoveries and the elucidation of a variety of biosynthetic pathways. Further, it also acts as an innovative tool for herbal medicine's scientific validation and quality assurance. This review highlights different strategies and analytical techniques employed in the practice of metabolomics. Further, it also discusses several other applications and advantages of metabolomics in the area of natural product chemistry. Additional examples of integrating metabolomics with multivariate data analysis techniques for some Indian medicinal plants are also reviewed. Recent technical advances in mass spectrometry-based hyphenated techniques, nuclear magnetic resonance-based techniques, and comprehensive hyphenated technologies for phytometabolite profiling studies have also been reviewed. Mass Spectral Imaging (MSI) has been presented as a highly promising method for high precision in situ spatiotemporal monitoring of phytometabolites. We conclude by introducing GNPS (Global Natural Products Social Molecular Networking) as an emerging platform to make social networks of related molecules, to explore data and to annotate more metabolites, and expand the networks to novel "predictive" metabolites that can be validated.

Chemical profiling and quantification of potential active constituents responsible for the antiplasmodial activity of Cissampelos pareira.

ETHNOPHARMACOLOGICAL RELEVANCE: Cissampelos pareira is used traditionally in India as a remedy for the treatment of various diseases including malaria but the active ingredients responsible for antiplasmodial activity have not yet been investigated. AIM OF THE STUDY: The identification and quantification of compounds responsible for antiplasmodial activity in different parts (leaf, stem and root) of C. pareira is the target of current study. MATERIAL AND METHODS: The hydro ethanolic parent extracts of different parts of C. pareira and fractions prepared from these extracts were evaluated against Pf3D7 (chloroquine sensitive) and PfINDO (chloroquine resistance) strains in culture to quantify the IC50 for extracts and fractions. Promising fractions of root part of plant were subjected to silica gel column chromatography to obtain pure compounds and their structures were elucidated by detailed spectroscopic analysis. Pure compounds were also tested against Pf3D7 and PfINDO strains. A rapid and simple UPLC-DAD method was developed for the identification and quantification of pharmaceutically important metabolites of C. pareira. RESULTS: Among different extracts, the hydro ethanolic extract of root part of C. pareira was found most active with IC50 values (µg/ml) of 1.42 and 1.15 against Pf 3D7 and Pf INDO, respectively. Tested against Pf 3D7 the most potent fractions were root ethyl acetate fraction (IC50 4.0 µg/ml), stem water fraction (IC50 4.4 µg/ml), and root water fraction (IC50 8.5 µg/ml). Further, phytochemical investigation of active fractions of root part led to the isolation and characterization of a new isoquinoline alkaloid, namely pareirarine (8), along with five known compounds magnoflorine (5), magnocurarine (10), salutaridine (11), cissamine (13) and hayatinine (15). Hayatinine (15), a bisbenzylisoquinoline alkaloid, isolated from root ethyl acetate fraction was most promising compound with IC50 of 0.41 µM (Pf INDO) and 0.509 µM (Pf 3D7). Magnocurarine (10) and cissamine (13) were also found active with IC50 values of 12.51 and 47.34 µM against Pf INDO and 12.54 and 8.76 µM against Pf 3D7, respectively. A total of thirty compounds were detected in studied extracts and fractions, structures were assigned to 15 of these and five of these biologically important compounds were quantified. Isolation of saluteridine (11) from C. pareira and the evaluation of antiplasmodial activity of pure compound from C. pariera is disclosed for the first time. CONCLUSION: This study concludes that the antimalarial potential of C. pareira may be attributed to isoquinoline type alkaloids present in this plant and also provides the scientific evidence for the traditional use of this plant in treatment of malaria.

Design, Synthesis, Structure-Activity Relationship and Docking Studies of Novel Functionalized Arylvinyl-1,2,4-Trioxanes as Potent Antiplasmodial as well as Anticancer Agents.

A novel series of synthetic functionalized arylvinyl-1,2,4-trioxanes (8 a-p) has been prepared and assessed for their in vitro antiplasmodial activity against the chloroquine-resistant Pf INDO strain of Plasmodium falciparum by using a SYBR green-I fluorescence assay. Compounds 8 g (IC50 =0.051 µM; SI=589.41) and 8 m (IC50 =0.059 µM; SI=55.93) showed 11-fold and >9-fold more potent antiplasmodial activity, respectively, as compared to chloroquine (IC50 =0.546 µM; SI=36.63). Different in silico docking studies performed on many target proteins revealed that the most active arylvinyl-1,2,4-trioxanes (8 g and 8 m) showed dihydrofolate reductase (DHFR) binding affinities on a par with those of chloroquine and artesunate. The in vitro cytotoxic potentials of 8 a-p were also evaluated against human lung (A549) and liver (HepG2) cancer cell lines along with immortalized normal lung (BEAS-2B) and liver (LO2) cell lines. Following screening, five derivatives viz. 8 a, 8 h, 8 l, 8 m and 8 o (IC50 =1.65-31.7 µM; SI=1.08-10.96) were found to show potent cytotoxic activity against (A549) lung cancer cell lines, with selectivity superior to that of the reference compounds artemisinin (IC50 =100 µM), chloroquine (IC50 =100 µM) and artesunic acid (IC50 =9.85 µM; SI=0.76). In fact, the most active 4-naphthyl-substituted analogue 8 l (IC50 =1.65 µM; SI >10) exhibited >60 times more cytotoxicity than the standard reference, artemisinin, against A549 lung cancer cell lines. In silico docking studies of the most active anticancer compounds, 8 l and 8 m, against EGFR were found to validate the wet lab results. In summary, a new series of functionalized aryl-vinyl-1,2,4-trioxanes (8 a-p) has been shown to display dual potency as promising antiplasmodial and anticancer agents.

Recent advances in inducing endophytic fungal specialized metabolites using small molecule elicitors including epigenetic modifiers.

Today when the quest of new lead molecules to supply the development pipeline is driving the course of drug discovery, endophytic fungi with their outstanding biosynthetic potential seem to be highly promising avenues for natural product scientists. However, challenges such as the production of inadequate quantities of compounds, the attenuation or loss of ability of endophytes to produce the compound of interest when grown in culture and the inability of fungal endophytes to express their full biosynthetic potential in laboratory conditions have been the major constraints. These have led to the application of small chemical elicitors that induce epigenetic changes in fungi to activate their silent gene clusters optimizing the amount of metabolites of interest or inducing the synthesis of hitherto undescribed compounds. In this respect small molecular weight compounds which are known to function as inhibitors of histone deacetylase (HDAC), DNA methyltransferase (DNMT) and proteasome have proven their efficacy in enhancing or inducing the production of specialized metabolites by fungi. Moreover, organic solvents, metals and plants extracts are also acknowledged for their ability to cause shifts in fungal metabolism. We highlight the successful studies from the past two decades reporting the ability of structurally diverse small molecular weight compounds to elicit the production of previously undescribed metabolites from endophytic fungi grown in culture. This mini review argues in favor of chemical elicitation as an effective strategy to optimize the production of fungal metabolites and invigorate the pipeline of drug discovery with new chemical entities.