Background/Aims: A multi-component enzyme system called NADPH oxidase (NOX) helps innate immunity by generating reactive oxygen species (ROS). NOX hyperactivation has been associated w several diseases. This enzyme is a membrane-bound complex made up of six subunits when it is active. These enzymatic subunits are considered to be potent inhibitors of enzyme activity and good targets for reducing oxidative stress. Methods: The present study aimed to analyze the possible targets: the different subunits of NOX, for their interactions with apocynin to identify its possible mechanism of inhibition for NOX, using in silico tools. Monomer, dimer, and trimer of apocynin were docked to various subunits of NOX. Results: Comparable glide scores were obtained when the monomer and dimer of apocynin were docked with p47phox complete subunit of NOX and were better than in comparison to trimer. Free Energy of Binding (FEB) was highest in the case of the trimer (-37.4 Kcal/mol), followed by the dimer (-21.2 Kcal/mol) and monomer (-18.2 Kcal/mol). Dimer obtained the highest glide score of 8.25 (FEB =-25.1 Kcal/mol) with p67phox-isoform 2. The PH domain of p47phox and the SH3 domain of p67phox have their own best binding energy with dimmer. While molecular docking with Rac-Zn-GD, P, dimer, and trimer have shown comparable FEB. The residues, on which the ligands were found to interact, were of major significance being present in those domains that vicinity to inhibit or activate the complex and are important for the protein structure and functioning. MDS studies have confirmed the findings that the Apocynin trimer molecule has superior stability and interactions with the enzyme complex. Conclusion: It can be concluded from the study that trimer and dimer have better interactions in terms of FEB with p67phox and p47phox, indicating the reported findings in the literature.

Aim & background: Drugs with multiple bioactive moieties have the advantages of multiple modes of action and fewer chances of drug resistance. In continuation of our previous work of developing hybrid antimalarials, we present herein the synthesis and antimalarial activity of two different series of 7-chloroquinoline-sulfonamide hybrids. Materials & methods: The first series of compounds were synthesized by using p-dodecylbenzenesulfonic acid as a Bronsted acid catalyst in ethanol. The second series' compounds were synthesized by 1,3-dipolar cycloaddition of azides and alkynes under click reaction conditions. Results & conclusion: The majority of these compounds demonstrated noncytotoxicity and significant antimalarial activity against Plasmodium falciparum (3D7) with IC50 values in the range of 1.49-13.49 μM. The most promising hybrids (12d, 13a and 13c) may be good starting points for next-generation antimalarials.

In spite of a decrease in malaria cases, the threat of malaria due to Plasmodium falciparum still prevails. The sequencing of Plasmodium falciparum reveals that approximately 60% of the Plasmodium genes code for hypothetical/putative proteins. Here we report an in silico characterization and localization of one such protein. This was encoded by one of the hub genes, in a weighted gene co-expression based systems network, from in-vivo samples of patients suffering from uncomplicated malaria or complicated malaria disease like jaundice and jaundice with renal failure. Interestingly, the protein PF3D7_0406000 (PFD0300w) is classified as a conserved protein of unknown function and shows no identity with any protein from the human host. The transcriptomic data shows up-regulation of transcripts in cases of malaria induced disease complications. PFD0300w peptide antibody based immunolocalization studies using a, gametocyte producing P. falciparum strain RKL-9, shows presence of the protein in the cytoplasm of both asexual and sexual stage parasites.

As the world gets closer to eliminating malaria, the scientific community worldwide has begun to realize the importance of malaria transmission-blocking interventions. The onus of breaking the life cycle of the human malaria parasite Plasmodium falciparum predominantly rests upon transmission-blocking drugs because of emerging resistance to commonly used schizonticides and insecticides. This third part of our review series on malaria transmission-blocking entails transmission-blocking potential of preclinical transmission-blocking antimalarials and other non-malaria drugs/experimental compounds that are not in clinical or preclinical development for malaria but possess transmission-blocking potential. Collective analysis of the structure and the activity of these experimental compounds might pave the way toward generation of novel prototypes of next-generation transmission-blocking drugs.

A series of benzenesulfonamide-appended [1,2,3]-triazole hybrids was synthesized by using [3 + 2] cycloaddition of primary, secondary, and tertiary sulfonamide azides with various phenoxymethylacetylenes under click reaction conditions. After structural characterization, the compounds were subjected to in-silico absorption, distribution, metabolism, excretion and toxicity (ADMET) screening to evaluate their drug-likeness and other pharmacokinetic parameters. Furthermore, their in vitro antiplasmodial potential was assessed against Plasmodium falciparum (3D7) strain, and some of the synthesized compounds displayed promising antimalarial potency. On cytotoxicity evaluation using MTT cell viability assay, the most active candidate N-(4,6-dimethylpyridin-2-yl)-4-(4-(4-nitrophenoxy)methyl)-1H-[1,2,3]-triazol-1-yl)benzenesulfonamide (14; IC50 6.2 mu g/mL) demonstrated CC50 7.5 mu g/mL against human hepatocarcinoma (HUH-7) cells.

Drug resistance in malaria parasites is one of the major stumbling blocks hindering the goal of malaria elimination. One of the major strategies to counter drug resistance is the development of new potent antimalarial drugs. In the present study, a series of novel sulfonamide based coumarin-[1,2,3]-triazole conjugates have been synthesized via Huisgen reaction between azidosulfonamides and 4-hydroxy- or 7-hydroxymethylcoumarinoalkynes. All the compounds have been characterized spectroscopically and screened for their in vitro antimalarial activity against P. falciparum 3D7 strain. Out of the twenty five synthesized compounds, four compounds displayed significant activity (IC50 <10 mu M) with the most active compound having an IC50 of 3.64 mu M.

The scientific community worldwide has realized that malaria elimination will not be possible without development of safe and effective transmission-blocking interventions. Primaquine, the only WHO recommended transmission-blocking drug, is not extensively utilized because of the toxicity issues in G6PD deficient individuals. Therefore, there is an urgent need to develop novel therapeutic interventions that can target malaria parasites and effectively block transmission. But at first, it is imperative to unravel the existing portfolio of transmission-blocking drugs. This review highlights transmission-blocking potential of current antimalarial drugs and drugs that are in various stages of clinical development. The collective analysis of the relationships between the structure and the activity of transmission-blocking drugs is expected to help in the design of new transmission-blocking antimalarials.

Novel 4-amino-7-chloroquinoline-based 1,2,3-triazole hybrids were synthesised in good yields by Cu-I-catalysed Huisgen 1,3-dipolar cycloaddition reactions of 2-azido-N-(7-chloroquinolin-4-ylaminoalkyl)acetamides with various terminal alkynes. These new hybrids were screened in vitro against asexual blood stages of the chloroquine-sensitive 3D7 strain of P. falciparum. The most active compounds were further screened against asexual and sexual stages (gametocytes) of the chloroquine-resistant RKL-9 strain of P. falciparum. Although all compounds were less potent than chloroquine against the 3D7 strain, the three best compounds were appreciably more active than chloroquine against the RKL-9 strain, displaying IC50 values of m, with one of them having an IC50 of 2.94 nm. Further, the lead compounds were gametocytocidal with IC50 values in the micromolar range, and were observed to induce morphological deformations in mature gametocytes. Most compounds demonstrated little or no cytotoxicity and exhibited good selectivity indices. The most active compounds represent promising candidates for further evaluation of their schizonticidal and gametocytocidal potential.

Background & objectives: Malaria has remained a global health problem despite the effective control and treatment measures. In the backdrop of drug resistance, developing novel hybrid molecules targeting the sexual stages (gametocytes) of the human malaria parasite Plasmodium falciparum is of great significance. Recently, chalcone- based polyphenols have generated a great interest in the malaria research community worldwide due to their ease of synthesis and significant biological activity. The primary objective of this study was to investigate the interaction of a newly synthesized quinoline-appended chalcone derivative (ADMQ) with gametocyte specific proteins, Pfg 27 and Pfs 25 and explore its in vitro gametocytocidal potential. Methods: The characterization of ligand-protein interactions at the atomistic level was done by a simulation strategy that combines molecular docking and molecular dynamics (MD) simulation in a coherent workflow. The X-ray crystal structure of Pfg 27 was retrieved from protein data bank and Pfs 25 was built using the Iterative Threading ASSembly Refinement (I-TASSER) server. The detailed interaction of both ADMQ and a known gametocytocidal agent, methylene blue (MB) (used as a positive control) with gametocyte proteins Pfg 27 and Pfs 25 was studied with a 50 ns explicit MD simulation. The ligand binding pose in terms of glide score, molecular mechanics-generalized born surface area (MM-GBSA) binding energies, protein-ligand root-mean-square-deviation (RMSD) and secondary structure elements (SSE) changes were analyzed accordingly. The direct effect of ADMQ on structural integrity of P. falciparum gametocytes was also examined using in vitro microscopy. Results: The analogous Glide score and MM-GBSA free energy of binding indicated stable interactions for both ADMQ and MB harboured in the active site of targeted gametocyte proteins, Pfg 27 and Pfs 25, separately. Explicit MD simulation by Desmond software package indicated similar distinguishable conformational changes in the active site of target polypeptide chain due to the specific accommodation of ADMQ molecule. The simulation also manifested comparable mechanistic profile in terms of protein-ligand RMSD and changes in secondary structure elements (SSE). Further, ADMQ treatment was found to adversely affect the structural integrity of gametocytes, which resulted in appearance of vesicles protruding from the gametocytes. Interpretation & conclusion: The consolidated in silico molecular modeling and in vitro study described herein may give an insight into the interaction patterns of quinoline-chalcone hybrids with critical gametocyte proteins in the mosquito. This study will possibly pave the way for further exploration of similar heterocyclic quinoline-chalcone hybrids to open up new avenues in drug candidate development against P. falciparum gametocytes.

Malaria still remains a global health problem despite of the availability of effective control and treatment measures. In the present study, a novel series of [1,2,3]-triazole tethered sulfonamide-berberine hybrids were synthesized in good yields viaHuisgen [3 +/- 2] cycloaddition reaction of various primary, secondary and tertiary sulfonamide based azides with 9-O-(propyne)berberine chloride in t-BuOH:water (1:1) mixture containing a catalytic amount of sodium ascorbate and CuSO4 center dot 5H(2)O at 90 degrees C. After spectroscopic characterization, these novel hybrids were evaluated for their potency against asexual erythrocytic stages of P. folcipoitim (3D7) in vitro. Most of the synthesized compounds have shown significant antimalarial activity with IC50 values in the range of 0.1-20 mu g/mL and were also found to be non-cytotoxic under tested conditions.

Background: Malaria remains a global health problem despite availability of effective tools. For malaria elimination, drugs targeting sexual stages of Plasmodium falciparum need to be incorporated in treatment regimen along with schizonticidal drugs to interrupt transmission. Primaquine is recommended as a transmission blocking drug for its effect on mature gametocytes but is not extensively utilized because of associated safety concerns among glucose-6-phosphate dehydrogenase (G6PD) deficient patients. In present work, methylene blue, which is proposed as an alternative to primaquine is investigated for its gametocytocidal activity amongst Indian field isolates. An effort has been made to establish Indian field isolates of P.falciparum as in vitro model for gametocytocidal drugs screening. Methods: Plasmodium falciparum isolates were adapted to in vitro culture and induced to gametocyte production by hypoxanthine and culture was enriched for gametocyte stages using N-acetyl-glucosamine. Gametocytes were incubated with methylene blue for 48 h and stage specific gametocytocidal activity was evaluated by microscopic examination. Results: Plasmodium falciparum field isolates RKL-9 and JDP-8 were able to reproducibly produce gametocytes in high yield and were used to screen gametocytocidal drugs. Methylene blue was found to target gametocytes in a concentration dependent manner by either completely eliminating gametocytes or rendering them morphologically deformed with mean IC50 (early stages) as 424.1 nM and mean IC50 (late stages) as 106.4 nM. These morphologically altered gametocytes appeared highly degenerated having shrinkage, distortions and membrane deformations. Conclusions: Field isolates that produce gametocytes in high yield in vitro can be identified and used to screen gametocytocidal drugs. These isolates should be used for validation of gametocytocidal hits obtained previously by using lab adapted reference strains. Methylene blue was found to target gametocytes produced from Indian field isolates and is proposed to be used as a gametocytocidal adjunct with artemisinin-based combination therapy. Further exploration of methylene blue in clinical studies amongst Indian population, including G6PD deficient patients, is recommended.

In the absence of clinically proven vaccines and emerging resistance to common antimalarials and insecticides, the onus of interrupting the life cycle of Plasmodium falciparum, is upon the transmission-blocking drugs. Current transmission-blocking drug primaquine finds its use restricted because of associated hemolytic toxicity issues in Glucose-6-Phosphate-Dehydrogenase deficient individuals. This article provides an extensive review of the assays used by the investigators to evaluate the transmission-blocking activity of drugs. Furthermore, limitations in existing transmission-blocking assessment approaches/studies are also covered in detail. This review is expected to help in the identification of lacunae in current understanding of transmission-blocking strategies, which are hindering our efforts to develop sustainable and effective transmission-blocking interventions.