Design and synthesis of chalcone derivatives as inhibitors of the ferredoxin - ferredoxin-NADP+ reductase interaction of Plasmodium falciparum: pursuing new antimalarial agents

Substituent and solvent effects on UV-visible absorption spectra of chalcones derivatives: Experimental and computational studies

The electronic spectra of the title compounds were measured in ethanol and cyclohexane. Three band systems are distinguished in the spectra of which the first and second band systems are attributed to local excitation of PhCH and PhCO rings. The third absorption band is assigned to a charge transfer (CT) band and is associated with the CO-CH=CH moiety. The solvent plays an important role in the absorption spectra and causes the CT band to consist of two electronic transitions. The effect of substituents on the phenyl rings on the charge transfer band of chalcone derivatives was also established in the two solvents. The converged gas-phase geometries of the studied chalcones was optimized using the DFT PBE0 functional with the basis set 6-311++G**. DFT calculations has been performed for an ethanol solution (using TD-PBE0/6-311++G**) level to understand electronic transitions on terms of energies and oscillator strengths to study the substituent effect on the electronic transitions of the chalcone derivatives. To consider the solvation effect of ethanol on the absorptions, the integral equation formalism variant of the polarizable continuum model (IEFPCM) was used. The calculated energies were in good agreement with experiment results. The molecular modelling technique was followed to monitor the effect of substitutions on the HOMO/LUMO energy and total dipole moment. Transitions between natural transition orbitals are also described as part of this study.

Antagonistic antimalarial properties of a methoxyamino chalcone derivative and 3-hydroxypyridinones in combination with dihydroartemisinin against Plasmodium falciparum

Background

The spread of artemisinin (ART)-resistant Plasmodium falciparum threatens the control of malaria. Mutations in the propeller domains of P. falciparum Kelch13 (k13) are strongly associated with ART resistance. Ferredoxin (Fd), a component of the ferredoxin/NADP⁺ reductase (Fd/FNR) redox system, is essential for isoprenoid precursor synthesis in the plasmodial apicoplast, which is important for K13-dependent hemoglobin trafficking and ART activation. Therefore, Fd is an antimalarial drug target and fd mutations may modulate ART sensitivity. We hypothesized that loss of Fd/FNR function enhances the effect of k13 mutation on ART resistance.

Methods

In this study, methoxyamino chalcone (C3), an antimalarial compound that has been reported to inhibit the interaction of recombinant Fd and FNR proteins, was used as a chemical inhibitor of the Fd/FNR redox system. We investigated the inhibitory effects of dihydroartemisinin (DHA), C3, and iron chelators including deferiprone (DFP), 1-(N-acetyl-6-aminohexyl)-3-hydroxy-2-methylpyridin-4-one (CM1) and deferiprone-resveratrol hybrid (DFP-RVT) against wild-type (WT), k13 mutant, fd mutant, and k13 fd double mutant P. falciparum parasites. Furthermore, we investigated the pharmacological interaction of C3 with DHA, in which the iron chelators were used as reference ART antagonists.

Results

C3 showed antimalarial potency similar to that of the iron chelators. As expected, combining DHA with C3 or iron chelators exhibited a moderately antagonistic effect. No differences were observed among the mutant parasites with respect to their sensitivity to C3, iron chelators, or the interactions of these compounds with DHA.

Discussion

The data suggest that inhibitors of the Fd/FNR redox system should be avoided as ART partner drugs in ART combination therapy for treating malaria.

In vitro and in silico assessment of new beta amino ketones with antiplasmodial activity

BACKGROUND

Based on the current need for new drugs against malaria, our study evaluated eight beta amino ketones in silico and in vitro for potential antimalarial activity.

METHODS

Using the Brazilian Malaria Molecular Targets (BraMMT) and OCTOPUS® software programs, the pattern of interactions of beta-amino ketones was described against different proteins of P. falciparum and screened to evaluate their physicochemical properties. The in vitro antiplasmodial activities of the compounds were evaluated using a SYBR Green-based assay. In parallel, in vitro cytotoxic data were obtained using the MTT assay.

RESULTS

Among the eight compounds, compound 1 was the most active and selective against P. falciparum (IC50 = 0.98 µM; SI > 60). Six targets were identified in BraMMT that interact with compounds exhibiting a stronger binding energy than the crystallographic ligand: P. falciparum triophosphate phosphoglycolate complex (1LYX), P. falciparum reductase (2OK8), PfPK7 (2PML), P. falciparum glutaredoxin (4N0Z), PfATP6, and PfHT.

CONCLUSIONS

The physicochemical properties of compound 1 were compatible with the set of criteria established by the Lipinski rule and demonstrated its potential as a drug prototype for antiplasmodial activity.

Synthesis of Chalcones Derivatives and Their Biological Activities: A Review

Chalcone derivatives are considered valuable species because they possess a ketoethylenic moiety, CO-CH=CH-. Due to the presence of a reactive α,β-unsaturated carbonyl group, chalcones and their derivatives possess a wide spectrum of antiproliferative, antifungal, antibacterial, antiviral, antileishmanial, and antimalarial pharmacological properties. Recent developments in heterocyclic chemistry have led to the synthesis of chalcone derivatives, which had been biologically investigated toward certain disease targets. The major aspect of this review is to present the most recent synthesis of chalcones bearing N, O, and/or S heterocycles, revealing their biological potential during the past decade (2010-2021). Based on a review of the literature, many chalcone-heterocycle hybrids appear to exhibit promise as future drug candidates owing to their similar or superior activities compared to those of the standards. Thus, this review may prove to be beneficial for the development and design of new potent therapeutic drugs based on previously developed strategies.

Chalcones as Anti-Glioblastoma Stem Cell Agent Alone or as Nanoparticle Formulation Using Carbon Dots as Nanocarrier

The current prognosis for glioblastoma is dismal. Treatment-resistant glioblastoma stem cells (GSCs) and the failure of most drugs to reach therapeutic levels within the tumor remain formidable obstacles to successful treatment. Chalcones are aromatic ketones demonstrated to reduce malignant properties in cancers including glioblastoma. Nanomedicines can increase drug accumulation and tumor cell death. Carbon-dots are promising nanocarriers that can be easily functionalized with tumor-targeting ligands and anti-cancer drugs. Therefore, we synthesized a series of 4′-amino chalcones with the rationale that the amino group would serve as a “handle” to facilitate covalent attachment to carbon-dots and tested their cytotoxicity toward GSCs. We generated 31 chalcones (22 4′-amino and 9 4′ derivatives) including 5 novel chalcones, and found that 13 had an IC₅₀ below 10 µM in all GSC lines. After confirming that the 4-amino group was not part of the active pharmacophore, chalcones were attached to transferrin-conjugated carbon-dots. These conjugates were significantly more cytotoxic than the free chalcones, with the C-dot-transferrin-2,5, dimethoxy chalcone conjugate inducing up to 100-fold more GSC death. Several of the tested chalcones represent promising lead compounds for the development of novel anti-GSC drugs. Furthermore, designing amino chalcones for carbon-dot mediated drug delivery is a rational and effective methodology.

Comparison of various synthesis methods and synthesis parameters of pyrazoline derivates

Pyrazoline plays an important role in the development of heterocyclic chemistry theory and is widely used as a synthesis useful in organic synthesis. The structure of the pyrazoline derivative compound contains a 5-membered heterocyclic framework with two nitrogen atoms and one endocyclic double bond. The function of pyrazoline as a fragment was stable enough in the bioactive group to synthesize new compounds with various biological activities. Various methods that could be used for the synthesis of pyrazole derivatives were ultrasonic irradiation, microwave assistance, ionic liquids, grinding techniques, and conventional methods. However, the synthesis of pyrazoline derivatives using conventional methods had many problems, one of which is the product yield, which was <70%. Therefore, this article will discuss the importance of optimizing the synthesis reaction conditions by taking into account several synthesis parameters to get the best organic product results based on conventional methods. A literature search was conducted by employing PubChem, Chemspider Google Scholar, Research Gate, Science Direct, and Elsevier by selecting pyrazoline synthesis based on physicochemical profile, reaction mechanism, and synthesis method.

Covalent inhibition of P. falciparum ferredoxin-NADP+ reductase: Exploring alternative strategies for the development of new antimalarial drugs

The protozoan Plasmodium falciparum is the main aetiological agent of tropical malaria. Characteristic of the phylum is the presence of a plastid-like organelle which hosts several homologs of plant proteins, including a ferredoxin (PfFd) and its NADPH-dependent reductase (PfFNR). The PfFNR/PfFd redox system is essential for the parasite, while mammals share no homologous proteins, making the enzyme an attractive target for novel and much needed antimalarial drugs. Based on previous findings, three chemically reactive residues important for PfFNR activity were identified: namely, the active-site Cys99, responsible for hydride transfer; Cys284, whose oxidation leads to an inactive dimeric form of the protein; and His286, which is involved in NADPH binding. These amino acid residues were probed by several residue-specific reagents and the two cysteines were shown to be promising targets for covalent inhibition. The quantitative and qualitative description of the reactivity of few compounds, including a repurposed drug, set the bases for the development of more potent and specific antimalarial leads.

Synthesis, characterization, in vitro cholinesterase and hRBCs hemolysis assay and computational evaluation of novel 2,3,4,5-tetrahydrobenzothiazepine appended α-aminophosphonates

A series of novel 2,3,4,5-tetrahydrobenzothiazepine appended α-aminophosphonate derivatives were synthesized by subjecting 2,3-dihydrobenzothiazepine to Pudovik reaction using diethyl phosphite. Tested derivatives exhibited better AChE inhibition (0.86-12.85 µM) when compared to BuChE (3.13-19.36 µM). Derivative 5f (IC₅₀ = 0.86 ± 0.08 µM), 5g (IC₅₀ = 1.05 ± 0.06 µM) and 5d (IC₅₀ = 1.64 ± 0.06 µM) exhibited higher AChE inhibitory activity as compared to standard drug galantamine (IC₅₀ = 2.15 ± 0.05 µM). Similarly, derivative 5e (IC₅₀ = 3.13 ± 0.11 µM) and 5f (IC₅₀ = 3.64 ± 0.06 µM) demonstrated comparable BuChE inhibitory activity to reference drug galantamine (IC₅₀ = 3.86 ± 0.03 µM). Further, enzyme kinetic studies were carried out for the most active molecule i.e. derivative 5f (for AChE) and derivative 5e (for BuChE) and the results imply that derivatives 5f and 5e show mixed-type inhibition with K_i values of 1.779 µM and 3.851 µM respectively. Enzyme reversibility inhibition studies demonstrated that all the tested derivatives possess reversible inhibitor characteristics. In addition, % hemolysis studies were carried out using human red blood cells (hRBCs) and the results demonstrated that the synthesized derivatives were biocompatible in nature as they impart very less cytotoxicity to hRBCs (CC₅₀ > 1000 μg/mL). Also, cell viability studies for tested derivatives revealed no cytotoxicity in N2a cells. Moreover, molecular docking studies revealed that derivative 5e and 5f bind to the PAS and CAS of the AChE. ADME predictions suggested that synthesized derivatives have high possibility of being drug-like.

Design, Synthesis, Characterization and in vivo Antidiabetic Activity Evaluation of Some Chalcone Derivatives

Background

Diabetes is one of the growing health problems worldwide, and scientists have been striving to find effective treatment methods. In this regard, chalcones have frequently been targeted by many researchers owing to their diverse biological activities.

Methods

Here, the Claisen-Schmidt condensation reaction was applied to synthesize five chalcone derivatives. The chalcone derivatives were evaluated for their relative antidiabetic activities in vivo using streptozotocin (STZ)-induced diabetic mice. Besides, the compounds were assessed for their reduction in postprandial hyperglycemia at 50 and 100 mg/kg dose levels against a standard drug, glibenclamide. In addition, the structure-activity relationship (SAR) was analyzed to determine the effect of structural modification in chalcones activity.

Results

A dose-dependent reduction in postprandial hyperglycemia was observed. The highest reduction in blood glucose level (BGL) was achieved by compound 3 at a dose of 100 mg/kg (39%). This was found to be even higher than glibenclamide (34.5%). In the STZ-induced diabetic animal model, all test compounds showed comparable efficacy with glibenclamide. The SAR analysis revealed that the incorporation of electron-donating groups at position 5 of the benzaldehyde ring and position 2 of the acetophenone ring is promising to increase the antihyperglycemic activities of chalcones.

Conclusion

The chalcone derivatives considered in this study could be used as potential lead compounds in the discovery of effective drugs to treat diabetes mellitus.

Roles of Ferredoxin-Dependent Proteins in the Apicoplast of Plasmodium falciparum Parasites

Ferredoxin (Fd) and ferredoxin-NADP+ reductase (FNR) form a redox system that is hypothesized to play a central role in the maintenance and function of the apicoplast organelle of malaria parasites. The Fd/FNR system provides reducing power to various iron-sulfur cluster (FeS)-dependent proteins in the apicoplast and is believed to help to maintain redox balance in the organelle. While the Fd/FNR system has been pursued as a target for antimalarial drug discovery, Fd, FNR, and the FeS proteins presumably reliant on their reducing power play an unknown role in parasite survival and apicoplast maintenance. To address these questions, we generated genetic deletions of these proteins in a parasite line containing an apicoplast bypass system. Through these deletions, we discovered that Fd, FNR, and certain FeS proteins are essential for parasite survival but found that none are required for apicoplast maintenance. Additionally, we addressed the question of how Fd and its downstream FeS proteins obtain FeS cofactors by deleting the FeS transfer proteins SufA and NfuApi. While individual deletions of these proteins revealed their dispensability, double deletion resulted in synthetic lethality, demonstrating a redundant role in providing FeS clusters to Fd and other essential FeS proteins. Our data support a model in which the reducing power from the Fd/FNR system to certain downstream FeS proteins is essential for the survival of blood-stage malaria parasites but not for organelle maintenance, while other FeS proteins are dispensable for this stage of parasite development. IMPORTANCE Ferredoxin (Fd) and ferredoxin-NADP+ reductase (FNR) form one of the few known redox systems in the apicoplast of malaria parasites and provide reducing power to iron-sulfur (FeS) cluster proteins within the organelle. While the Fd/FNR system has been explored as a drug target, the essentiality and roles of this system and the identity of its downstream FeS proteins have not been determined. To answer these questions, we generated deletions of these proteins in an apicoplast metabolic bypass line (PfMev) and determined the minimal set of proteins required for parasite survival. Moving upstream of this pathway, we also generated individual and dual deletions of the two FeS transfer proteins that deliver FeS clusters to Fd and downstream FeS proteins. We found that both transfer proteins are dispensable, but double deletion displayed a synthetic lethal phenotype, demonstrating their functional redundancy. These findings provide important insights into apicoplast biochemistry and drug development.

C3 amino-substituted chalcone derivative with selective adenosine rA1 receptor affinity in the micromolar range

ABSTRACT

To identify novel adenosine receptor (AR) ligands based on the chalcone scaffold, herein the synthesis, characterization and in vitro and in silico evaluation of 33 chalcones (15-36 and 37-41) and structurally related compounds (42-47) are reported. These compounds were characterized by radioligand binding and GTP shift assays to determine the degree and type of binding affinity, respectively, against rat (r) A1 and A2A ARs. The chalcone derivatives 24, 29, 37 and 38 possessed selective A1 affinity below 10 µM, and thus, are the most active compounds of the present series; compound 38 was the most potent selective A1 AR antagonist (K i (r) = 1.6 µM). The structure-affinity relationships (SAR) revealed that the NH2-group at position C3 of ring A of the chalcone scaffold played a key role in affinity, and also, the Br-atom at position C3' on benzylidene ring B. Upon in vitro and in silico evaluation, the novel C3 amino-substituted chalcone derivative 38-that contains an α,ß-unsaturated carbonyl system and easily allows structural modification-may possibly be a synthon in future drug discovery.

GRAPHIC ABSTRACT

C3 amino-substituted chalcone derivative (38) with C3' Br substitution on benzylidene ring B possesses selective adenosine rA1 receptor affinity in micromolar range.

Reactions of Plasmodium falciparum Ferredoxin:NADP+ Oxidoreductase with Redox Cycling Xenobiotics: A Mechanistic Study

Ferredoxin:NADP⁺ oxidoreductase from Plasmodium falciparum (PfFNR) catalyzes the NADPH-dependent reduction of ferredoxin (PfFd), which provides redox equivalents for the biosynthesis of isoprenoids and fatty acids in the apicoplast. Like other flavin-dependent electrontransferases, PfFNR is a potential source of free radicals of quinones and other redox cycling compounds. We report here a kinetic study of the reduction of quinones, nitroaromatic compounds and aromatic N-oxides by PfFNR. We show that all these groups of compounds are reduced in a single-electron pathway, their reactivity increasing with the increase in their single-electron reduction midpoint potential (E¹₇). The reactivity of nitroaromatics is lower than that of quinones and aromatic N-oxides, which is in line with the differences in their electron self-exchange rate constants. Quinone reduction proceeds via a ping-pong mechanism. During the reoxidation of reduced FAD by quinones, the oxidation of FADH^. to FAD is the possible rate-limiting step. The calculated electron transfer distances in the reaction of PfFNR with various electron acceptors are similar to those of Anabaena FNR, thus demonstrating their similar “intrinsic” reactivity. Ferredoxin stimulated quinone- and nitro-reductase reactions of PfFNR, evidently providing an additional reduction pathway via reduced PfFd. Based on the available data, PfFNR and possibly PfFd may play a central role in the reductive activation of quinones, nitroaromatics and aromatic N-oxides in P. falciparum, contributing to their antiplasmodial action.

Synthesis and in vitro anti-proliferative evaluation of naphthalimide–chalcone/pyrazoline conjugates as potential SERMs with computational validation

A series of naphthalimide-chalcone/pyrazoline conjugates was prepared and evaluated for their anti-breast cancer potential against estrogen responsive, i.e. MCF-7 (ER+), and triple-negative, i.e. MDA-MB-231 (ER−), cell lines. The structure-activity-relationship (SAR) was deduced based on the influence of linker length, substituents on the phenyl ring and the generated functionalities, on anti-proliferative activities. Docking simulations further delineate the type of interactions of the designed molecules with the selected targets. This report discloses the scope of triazole tethered naphthalimide-chalcone/pyrazoline conjugates as anti breast cancer agents.

Design, synthesis and anti-proliferative evaluation of naphthalimide–chalcone/pyrazoline conjugates.

Synthesis and Biological Evaluation of Novel Aminochalcones as Potential Anticancer and Antimicrobial Agents

A series of 18 aminochalcone derivatives were obtained in yields of 21.5-88.6% by applying the classical Claisen-Schmidt reaction. Compounds 4-9, 14 and 16-18 with 4-ethyl, 4-carboxy-, 4-benzyloxy- and 4-benzyloxy-3-methoxy groups were novel, not previously described in the scientific literature. To determine the biological properties of the synthesized compounds, anticancer and antimicrobial activity assays were performed. Antiproliferative potential was evaluated on four different human colon cancer cell lines-HT-29, LS180, LoVo and LoVo/DX -using the SRB assay and compared with green monkey kidney fibroblasts COS7. Anticancer activity was described as the IC50 value. The best results were observed for 2'-aminochalcone (1), 3'-aminochalcone (2) and 4'-aminochalcone (3) (IC50 = 1.43-1.98 µg·mL-1) against the HT-29 cell line and for amino-nitrochalcones 10-12 (IC50 = 2.77-3.42 µg·mL-1) against the LoVo and LoVo/DX cell lines. Moreover, the antimicrobial activity of all derivatives was evaluated on two strains of bacteria: Escherichia coli ATCC10536 and Staphylococcus aureus DSM799, the yeast strain Candida albicans DSM1386 and three strains of fungi: Alternaria alternata CBS1526, Fusarium linii KB-F1 and Aspergillus niger DSM1957. In the case of E. coli ATCC10536 almost all derivatives hindered the bacterial growth (∆OD = 0). Furthermore, the best results were observed in the presence of 4'-aminochalcone (3), that completely limited the growth of all tested strains at the concentration range of 0.25-0.5 mg·mL-1. The strongest bacteriostatic activity was exhibited by novel 3'-amino-4-benzyloxychalcone (14), that prevented the growth of E. coli ATCC10536 with MIC = 0.0625 mg·mL-1.

Evaluation of Novel Chalcone-Thiosemicarbazones Derivatives as Potential Anti-Leishmania amazonensis Agents and Its HSA Binding Studies

A series of seven chalcone-thiosemicarbazones (5a-5g) were synthesized and evaluated as potential new drugs (anti-leishmanial effect). Although four of the chalcone-thiosemicarbazones are already known, none of them or any compound in this class has been previously investigated for their effects on parasites of the Leishmania genus. The compounds were prepared in satisfactory yields (40-75%) and these compounds were evaluated against promastigotes, axenic amastigotes and intracellular amastigotes of L. amazonensis after 48 h of culture. The half maximal inhibitory concentration (IC₅₀) values of the intracellular amastigotes were determined to be in the range of 3.40 to 5.95 µM for all compounds assayed. The selectivity index showed value of 15.05 for 5a, whereas pentamidine (reference drug) was more toxic in our model (SI = 2.32). Furthermore, to understand the preliminary relationship between the anti-leishmanial activity of the chalcone-thiosemicarbazones, their electronic (σ), steric (MR) and lipophilicity (π) properties were correlated, and the results indicated that moieties with electronic withdrawing effects increase the anti-leishmanial activity. The preliminary pharmacokinetic evaluation of one of the most active compound (5e) was studied via interaction to human serum albumin (HSA) using multiple spectroscopic techniques combined with molecular docking. The results of antiparasitic effects against L. amazonensis revealed the chalcone-thiosemicarbazone class to be novel prototypes for drug development against leishmaniasis.

Design and Synthesis of Benzimidazole-Chalcone Derivatives as Potential Anticancer Agents

Numerous reports have shown that conjugated benzimidazole derivatives possess various kinds of biological activities, including anticancer properties. In this report, we designed and synthesized 24 new molecules comprising a benzimidazole ring, arene, and alkyl chain-bearing cyclic moieties. The results showed that the N-substituted benzimidazole derivatives bearing an alkyl chain and a nitrogen-containing 5- or 6-membered ring enhanced the cytotoxic effects on human breast adenocarcinoma (MCF-7) and human ovarian carcinoma (OVCAR-3) cell lines. Among the 24 synthesized compounds, (2E)-1-(1-(3-morpholinopropyl)-1H-benzimidazol-2 -yl)-3-phenyl-2-propen-1-one) (23a) reduced the proliferation of MCF-7 and OVCAR-3 cell lines demonstrating superior outcomes to those of cisplatin.

5-(4-Bromophenyl)-7-(2,4-dimethoxyphenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine

A derivative of dihydrotetrazolopyrimidine has been successfully synthesized through a cyclocondensation reaction between a chalcone derivative with 5-aminotetrazole. The molecular structure of the title compound was established based on Fourier transform infrared spectra (FTIR), high-resolution mass spectrometry (HRMS), 1D and 2D nuclear magnetic resonance (NMR) spectrum.

(E)-3-[3-(4-Morpholinophenyl)acryloyl]-2H-chromen-2-one

A new compound (E)-3-[3-(4-morpholinophenyl)acryloyl]-2H-chromen-2-one, a coumarin based chalcone derivative, has been successfully synthesized employing a molecular hybridization method through the reaction between 3-acetylcoumarin and 4-morpholinobenzaldehyde using a Claisen–Schmidt reaction using pTSA as a catalyst. The structure of the title compound was established using spectroscopic data FTIR, HRESI-MS, 1H- and 13C-NMR. The anticancer activity against breast cancer cells line T47D and cervix cancer cells line HeLa was determined using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay.

Plasmodium-specific basic amino acid residues important for the interaction with ferredoxin on the surface of ferredoxin-NADP+ reductase

The malaria parasite (Plasmodium falciparum) possesses a plastid-derived, essential organelle called the apicoplast, which contains a redox system comprising plant-type ferredoxin (Fd) and Fd-NADP+ reductase (FNR). This system supplies reducing power for the crucial metabolic pathways in this organelle. Electron transfer between P. falciparum Fd (PfFd) and FNR (PfFNR) is performed with higher affinity and specificity than that of plant Fd and FNR. To investigate the mechanism for such superior protein-protein interaction, we searched for the Fd interaction sites on the surface of PfFNR. Basic amino acid residues on the FAD binding side of PfFNR were comprehensively substituted to acidic amino acids by site-directed mutagenesis. Kinetic analysis of electron transfer to PfFd and plant Fds, physical binding to immobilized PfFd and thermodynamics of the PfFd binding using these PfFNR mutants revealed that several basic amino acid residues including those in Plasmodium-specific insertion region are important for the interaction with PfFd. Majority of these basic residues are Plasmodium-specific and not conserved among plant and cyanobacteria FNRs. These results suggest that the interaction mode of Fd and FNR is diverged during evolution so that PfFd: PfFNR interaction meets the physiological requirement in the cells of Plasmodium species.

(E)-1-(2′,4′-Dimethyl)-(5-acetylthiazole)-(2,4″-difluorophenyl)-prop-2-en-1-one

Thiazole and chalcone motifs are of research interest to medicinal chemists due to their array of synthetic and biological utility. Hence, in the present study we intended to prepare (E)-1-(2′,4′-dimethyl)-(5-acetylthiazole)-(2,4″-difluorophenyl)-prop-2-en-1-one (3c) containing both these scaffolds. The compound 3c was synthesized by the acid-catalyzed condensation of 2,4-dimethyl-5-acetylthiazole with 2,4-difluorobenzaldehyde. Purification and characterization of the compound were carried out by recrystallization and spectral techniques including UV, IR, 1H-NMR, 13C-NMR, Mass spectrometry and X-ray powdered diffractometry. The molecule 3c was successfully synthesized, purified, and characterized.

Inhibitory Activity and Docking Analysis of Antimalarial Agents from Stemona sp. toward Ferredoxin-NADP+ Reductase from Malaria Parasites

Ferredoxin-NADP⁺ reductases (FNRs, EC 1.18.1.2) were found in the plastids of Plasmodium and have been considered as a target for the development of new antimalarial agents. Croomine, epi-croomine, tuberostemonine, javastemonine A, and isoprotostemonine are isolated alkaloids from the roots of Stemona sp. and their inhibitory effect on FNRs from Plasmodium falciparum (PfFNR) was investigated. Croomine showed the highest level of inhibition (33.9%) of electron transfer from PfFNR to PfFd, while tuberstemonine displayed the highest level of inhibition (55.4%) of diaphorase activity of PfFNR. Docking analysis represented that croomine is located at the middle position of PfFNR and PfFd. Croomine from S. tuberosa appeared to have potential as an antimalarial agent.

Synthesis of chalcone-imide derivatives and investigation of their anticancer and antimicrobial activities, carbonic anhydrase and acetylcholinesterase enzymes inhibition profiles

The new 1-(4-(3-(aryl)acryloyl)phenyl)-1H-pyrrole-2,5-diones (5a-g) were prepared from 4'-aminchalcones (3a-g) and screened for biological activities. All compounds (3a-g and 5a-g), except 3d and 3e displayed good cytotoxic activities with IC₅₀ values in the range of 7.06-67.46 μM. IC₅₀ value of 5-fluorouracil (5-FU) was 90.36 μM. Moreover, most of compounds 5a-g showed high antibacterial activity with 8-20 mm of inhibition zone (19-25 mm of Sulbactam-Cefoperazone (SCF)). In addition, they showed good inhibitory action against acetylcholinesterase (AChE), and human carbonic anhydrase I, and II (hCA I and hCA II) isoforms. Also, these compounds demonstrated effective inhibition profiles with Ki values of 426.47-699.58 nM against hCA I, 214.92-532.21 nM against hCA II, and 70.470-229.42 nM against AChE. On the other hand, acetazolamide, clinically used drug, showed a Ki value of 977.77 ± 227.4 nM against CA I, and 904.47 ± 106.3 nM against CA II, respectively. Also, tacrine inhibited AChE showed a Ki value of 446.56 ± 58.33 nM.