Antimalarial activity of Gomphostemma crinitum leaf extracts

Abstract  Antimalarial efficacy of Gomphostemma crinitum leaf extracts were studied in vitro against the chloroquine-sensitive MRC-02 strain of Plasmodium falciparum. The CHCl₃ extract (IC₅₀ 37.28 μg/mL) was found to be better than the aqueous extract (IC₅₀ 111.4 μg/mL). The major compound present in CHCl₃ extract was coded as GC-7 (12,17-diacetoxy, 15-hydroxy, 2-oxo, 3, 13 E (14)-diene clerodane). Seasonal variation of GC-7 was studied and correlated to the antimalarial efficacy of the crude extracts of leaves collected in different months. GC-7 was found to be the only regular compound present in G. crinitum leaves throughout the year. A good correlation between antimalarial efficacy (IC₅₀ 9.3 μg/mL) and concentration of GC-7 in crude extracts was observed. The mode of action of GC-7 was found to be different from that of chloroquine. Graphical Abstract  Antimalarial activity of Gomphostemma crinitum leaf extracts B.N Acharya, Deepika Saraswat and M.P Kaushik^* Discovery Centre, Process Technology Development Division Defence R & D Establishment, Jhansi Road, Gwalior-474002 (MP) INDIA ^#Entomology division, Defence Research and Development Establishment,Gwalior-474002, India Antimalarial activity of chloroform extract of G. crinitum leaves and an isolated compound GC-7 (12,17-diacetoxy,15-hydroxy,2-oxo,3,13 E (14)-diene clerodane) against a chloroquine susceptible strain of Plasmodium falciparum is described.     

Synthesis and biological evaluation of α, β-unsaturated ketone as potential antifungal agents

Abstract  With the aim of developing potential antifungals, a series of chalcones incorporating sulfur either as part of a heteroaromatic ring (thiophene) or as a side chain (thiomethyl group) were synthesized and tested for their in vitro activity. Some of the compounds showed appreciable activity against a fluconazole-resistant strain, and could act as new hits for the design of better analogs. Graphical Abstract  Synthesis and biological evaluation of α,β-unsaturated ketone as potential antifungal agentsSeema Bag, S.Ramar, Mariam S. Degani*With an aim to develop new chemical entities with potent antifungal activity against Candida albicans strains, a series of chalcones incorporating sulfur either as part of a heteroaromatic ring (thiophene) or as a side chain (thiomethyl group) were synthesized. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Potent antimalarial activity of newly synthesized substituted chalcone analogs in vitro

Abstract   Several new chalcone analogues were synthesized and evaluated as inhibitors of malaria parasite. Inhibitory activity was determined in vitro against a chloroquine-sensitive Plasmodium falciparum strain of parasites. The compound 3-(4-methoxyphenyl)-1-(4-pyrrol-1-yl-phenyl)prop-2-en-1-one was found to be the most active with 50% inhibition concentration (IC₅₀) of 1.61 μg/ml. This inhibitory concentration is comparable to a prototype phytochemical chalcone, licochalcone A, with an IC₅₀ of 1.43 μg/ml. The present study suggests that small, lipophilic nitrogen heterocyclic ring A together with small hydrophobic functionality at ring B can enhance antimalarial activity. These results suggest that chalcones are a class of compounds that provides an option of developing inexpensive, synthetic therapeutic antimalarial agents in the future. Graphical Abstract  Claisen-Schmidt condensation method was employed to synthesize various substituted chalcones. Among all, 3-(4-Methoxyphenyl)-1-(4-pyrrol-1-yl-phenyl)prop-2-en-1-one was found to be most effective with IC₅₀ value of 1.6 μg/ml in vitro against chloroquine sensitive strain (3D7) of Plasmodium falciparum.      

New Compounds Hybrids 1H‐1,2,3‐Triazole‐Quinoline Against Plasmodium falciparum

Malaria is one of the most prevalent parasitic diseases in the world. The global importance of this disease, current vector control limitations, and the absence of an effective vaccine make the use of therapeutic antimalarial drugs the main strategy to control malaria. Chloroquine is a cost‐effective antimalarial drug with a relatively robust safety profile, or therapeutic index. However, chloroquine is no longer used alone to treat patients with Plasmodium falciparum due to the emergence and spread of chloroquine‐resistant strains, which have also been reported for Plasmodium vivax. However, the activity of 1,2,3‐triazole derivatives against chloroquine‐sensitive and chloroquine‐resistant strains of P. falciparum has been reported in the literature. To enhance the anti‐P. falciparum activity of quinoline derivatives, we synthesized 11 new quinoline‐1H‐1,2,3‐triazole hybrids with different substituents in the 4‐positions of the 1H‐1,2,3‐triazole ring, which were assayed against the W2‐chloroquine‐resistant P. falciparum clone. Six compounds exhibited activity against the P. falciparum W2 clone, chloroquine‐resistant, with IC₅₀ values ranging from 1.4 to 46 μm . None of these compounds was toxic to a normal monkey kidney cell line, thus exhibiting good selectivity indexes, as high 351 for one compound ( 11 ).     

Lipophilic 2-(4-chlorophenyl)-4-thiazolyl-1,4-dihydropyridines: synthesis, calcium channel antagonist activity, and protection against pentylenetetrazole-induced seizure

Abstract  A series of alkyl, cycloalkyl, and aryl esters of nifedipine in which the o-nitrophenyl group at position 4 is replaced by 2-(4-chlorophenyl)-4-thiazolyl substituent were synthesized and evaluated for their calcium channel antagonist activities using isolated ileum of guinea pig. The anticonvulsant activity of test drugs was also assessed in pentylenetetrazole (PTZ)-induced seizure in male Naval Medical Research Institute (NMRI) mice model. The results showed that although all compounds were at least 100 times less active than the reference drug nifedipine in terms of calcium channel antagonist activity, nevertheless all compounds showed considerable anticonvulsant activity. Graphical Abstract  A new series of alkyl, cycloalkyl and aryl substituted 4-chlorophenylthiazolyl–1,4-dihydropyridines were synthesized and tested for calcium channel inhibitory and anticonvulsant activities.      

Amide Tethered 4-Aminoquinoline-naphthalimide Hybrids: A New Class of Possible Dual Function Antiplasmodials

A series of amide tethered 4-aminoquinoline-naphthalimide hybrids has been synthesized to assess their in vitro antiplasmodial potential against chloroquine-susceptible (3D7) and chloroquine-resistant (W2) strains of Plasmodium falciparum. The most active and noncytotoxic compound had an IC₅₀ value of 0.07 μM against W2 strain and was more active than standard antimalarial drugs, including chloroquine, desethylamodiaquine, and quinine, particularly for drug resistant malaria. The promising scaffold, when subjected to heme binding and molecular modeling studies, was identified as a possible potent inhibitor of hemozoin formation and P. falciparum chloroquine resistance transporter (PfCRT), respectively, and, therefore, could act as a dual function antiplasmodial.     

Two new bisindole alkaloids from Tabernaemontana macrocarpa Jack

Two new bisindole alkaloids, bisnaecarpamines A (1) and B (2), possessing a vobasine-sarpagine type skeleton were isolated from the bark of Tabernaemontana macrocarpa Jack. Their structures were elucidated by extensive spectroscopic methods and chemical correlation. The absolute configurations of compounds 1 and 2 were established using TDDFT-ECD calculation of the selected isomers. Bisnaecarpamine A exhibited potent antimalarial activity against Plasmodium falciparum 3D7 strain with IC₅₀ value of 28.8 µM.

Graphic abstract

     

Pharmacophore-based predictive model generation for potent antimalarials targeting haem detoxification pathway

Pharmacophore hypotheses were developed for molecules having antimalarial activities targeting the haem detoxification pathway of the malaria parasite. A training set consisting of 23 compounds was selected to generate these hypotheses, and their activities were evaluated for haem polymerization inhibition and against chloroquine-sensitive (3D7) as well as chloroquine-resistant (K1) strains of p. falciparum. The models were cross-validated by Fischer’s randomization test at a 95% confidence level. The model developed against chloroquine-resistant malaria parasites was found to yield the best predictions among the three models.     

Synthesis,Docking, In Vitro and In Vivo Antimalarial Activity of Hybrid 4‐aminoquinoline–1,3,5‐triazine Derivatives Against Wild and Mutant Malaria Parasites

A new series of hybrid 4‐aminoquinoline–1,3,5‐triazine derivatives was synthesized by a four‐step reaction. Target compounds were screened for in vitro antimalarial activity against chloroquine‐sensitive (3D‐7) and chloroquine‐resistant (RKL‐2) strains of Plasmodium falciparum. Compounds exhibited, by and large, good antimalarial activity against the resistant strain, while two of them, that is 8g and 8a, displayed higher activity against both the strains of P. falciparum. Additionally, docking study was performed on both wild (1J3I.pdb) and quadruple mutant (N51I, C59R, S108 N, I164L, 3QG2.pdb) type pf‐DHFR‐TS to highlight the structural features of hybrid molecules.     

Synthesis, antibacterial, and antifungal activities of biolabile (E)-1-(4-morpholinophenyl)-3-aryl-prop-2-en-1-ones

Abstract  A collection of biolabile (E)-1-(4-morpholinophenyl)-3-aryl-prop-2-en-1-ones 8–13 are synthesized, characterized by melting point, elemental analysis, mass spectroscopy (MS), Fourier-transform infrared (FT-IR), and ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopic data and evaluated for their in vitro antibacterial and antifungal activities. Compounds 8–13 exerted a wide range of antibacterial activities against all tested Gram-positive and Gram-negative bacterial strains. All the compounds 8–13 were more active against Pseudomonas. Of the synthesized compounds, compounds 9 and 11 exhibited a wide range of antibacterial activities against Staphylococcus aureus, β-Heamolytic streptococcus, Escherichia coli, Klebsiella pneumonia, and Pseudomonas. Compounds 10, 12, and 13 exerted strong antifungal activities against all tested fungal strains, namely Aspergillus flavus, Mucor, Rhizopus, and Microsporum gypsuem. Graphical Abstract        

Design,synthesis and in vitro antiplasmodial activity of some bisquinolines against chloroquine‐resistant strain

A series of novel bisquinoline compounds comprising N¹‐(7‐chloroquinolin‐4‐yl) ethane‐1,2‐diamine and 7‐chloro‐N‐(2‐(piperazin‐1‐yl)ethyl)quinolin‐4‐amine connected with 7‐chloro‐4‐aminoquinoline containing various amino acids is described. We have bio‐evaluated the compounds against both chloroquine‐sensitive (3D7) and chloroquine‐resistant (K1) strains of Plasmodium falciparum in vitro. Among the series, compounds 4 and 7 exhibited 1.8‐ and 10.6‐fold superior activity as compared to chloroquine (CQ; IC₅₀ = 0.255 ± 0.049 μm ) against the K1 strain with IC₅₀ values 0.137 ± 0.014 and 0.026 ± 0.007 μm , respectively. Furthermore, compound 7 also displayed promising activity against the 3D7 strain (IC₅₀ = 0.024 ± 0.003 μm ) of P. falciparum when compared to CQ. All the compounds in the series displayed resistance factor between 0.57 and 4.71 as against 51 for CQ. These results suggest that bisquinolines can be explored for further development as new antimalarial agents active against chloroquine‐resistant P. falciparum.     

Novel 4-Aminoquinoline-Pyrimidine Based Hybrids with Improved in Vitro and in Vivo Antimalarial Activity

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Synthesis,Antiplasmodial Activity,and β-Hematin Inhibition of Hydroxypyridone–Chloroquine Hybrids

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Secochiliolide ester derivatives: Preparation and evaluation of their antitrypanosomal and antimalarial efficacy

In the present study, a series of new esters of secochiliolide acid (SA), a diterpene isolated from Nardophyllum bryoides, were synthesized in good yield. All compounds were evaluated for their in vitro antiparasitic properties (on Plasmodium falciparum and Trypanosoma brucei brucei) and cytotoxicity (on WI38, normal mammalian cells). They displayed moderate antitrypanosomal activity with IC₅₀ values between 2.55 and 18.14 μm , with selectivity indices >10, and low antiplasmodial effects with IC₅₀ > 29 μm . The only exception was the n‐hexyl ester of SA, which showed a strong and selective antiplasmodial activity (IC₅₀ = 1.99 μm and selectivity index = 117.0). The in vivo antimalarial efficacy of this compound was then assessed according to the 4‐day suppressive test of Peters in mice. An intraperitoneal treatment at 50 mg kg^?1 day^?1 induced a slight parasitaemia reduction by 56% which was statistically significant on day 4 post‐infection and an increase in the survival time.     

7‐Chloroquinoline–isatin Conjugates: Antimalarial,Antitubercular, and Cytotoxic Evaluation

A series of twenty piperazine‐tethered 7‐chloroquinoline–isatin hybrids have been synthesized via either direct nucleophilic substitution or Cu(Ι)Cl‐mediated Mannich reaction. These new conjugates were evaluated for their antimalarial and antitubercular efficacy against a chloroquine‐resistant strain of Plasmodium falciparum and Mycobacterium tuberculosis, respectively, while the cytotoxic profiles were evaluated against 3T6 cell line, a permanent mouse embryonic fibroblast cell line. The most potent of the test compound with IC₅₀ of 0.22 μm against W2 strain of P. falciparum and 31.62 μm against the embryonic fibroblast cell line (cytotoxicity) displayed a high selective index of 143.73.     

Antioxidant and antigenotoxic effects of rosemary (Rosmarinus officinalis L.) extracts in Salmonella typhimurium TA98 and HepG2 cells

In the present study the chemopreventive effects of water soluble AquaROX^® 15 and oil soluble VivOX^® 40 rosemary extracts against 4-nitroquinoline-N-oxide (NQNO) and 2-amino-3-methyl-3H-imidazo[4,5-F]quinoline (IQ) induced mutagenicity in the reverse mutation assays with Salmonella typhimurium TA98 and against t-butyl hydroperoxide (t-BOOH), benzo(a)pyrene (BaP) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induced DNA damage in HepG2 cells were studied, applying the comet assay. The results showed comparable protective effect of AquaROX and VivOX against oxidative DNA damage, whereas protection against indirect active genotoxic carcinogens was more efficient by VivOX.     

In vitro antimalarial activity of prenylated flavonoids from Erythrina fusca

Ethyl acetate (EtOAc) extract from the stem bark of Erythrina fusca showed a antimalarial activity against the multi-drug-resistant strain (K1) of Plasmodium falciparum, and six flavonoids, lupinifolin (1), citflavanone (2), erythrisenegalone (3), lonchocarpol A (4), liquiritigenin (5), and 8-prenyldaidzein (6), were isolated from the extract. Diprenylated flavanone 4 showed a notable antimalarial activity (IC₅₀; 1.6 μg/mL); however 1 and 3 did not show the activity, even though these compounds possessed prenylated substitution.     

Antimalarial and Structural Studies of Pyridine-Containing Inhibitors of 1-Deoxyxylulose-5-phosphate Reductoisomerase

d-xylulose-5-phosphate reductoisomerase (DXR) in the nonmevalonate isoprene biosynthesis pathway is a target for developing antimalarial drugs. Fosmidomycin, a potent DXR inhibitor, showed safety as well as efficacy against Plasmodium falciparum malaria in clinical trials. On the basis of our previous quantitative structure–activity relationship (QSAR) and crystallographic studies, several novel pyridine-containing fosmidomycin derivatives were designed, synthesized, and found to be highly potent inhibitors of P. falciparum DXR (PfDXR) having K_i values of 1.9–13 nM, with the best one being ∼11× more active than fosmidomycin. These compounds also potently block the proliferation of multidrug resistant P. falciparum with EC₅₀ values as low as 170 nM. A 2.3 Å crystal structure of PfDXR in complex with one of the inhibitors is reported, showing that the flexible loop of the protein undergoes conformational changes upon ligand binding and a hydrogen bond and favorable hydrophobic interactions between the pyridine group and the PfDXR account for the enhanced activity.     

Antimalarial Effect of 3‐Methoxy‐1,2‐Dioxetanes on the Erythrocytic Cycle of Plasmodium falciparum

The antimalarial activity of peroxides most likely originates from their interaction with iron(II) species located inside the malaria parasite, which forms destructive radical species through a Fenton‐like mechanism. This article reports the first evaluation of the in vitro antimalarial activity of three peroxides of the class 1,2‐dioxetanes against Plasmodium falciparum; the results reveal that the studied 3‐methoxy‐1,2‐dioxetanes display significant antimalarial activity, at a similar level as artemisinin and also that their reactivity toward iron(II) correlate linearly with their antimalarial activity.