An iron-sulfur cluster in the zinc-binding domain of the SARS-CoV-2 helicase modulates its RNA-binding and -unwinding activities.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, uses an RNA-dependent RNA polymerase along with several accessory factors to replicate its genome and transcribe its genes. Nonstructural protein (nsp) 13 is a helicase required for viral replication. Here, we found that nsp13 ligates iron, in addition to zinc, when purified anoxically. Using inductively coupled plasma mass spectrometry, UV-visible absorption, EPR, and Mössbauer spectroscopies, we characterized nsp13 as an iron-sulfur (Fe-S) protein that ligates an Fe4S4 cluster in the treble-clef metal-binding site of its zinc-binding domain. The Fe-S cluster in nsp13 modulates both its binding to the template RNA and its unwinding activity. Exposure of the protein to the stable nitroxide TEMPOL oxidizes and degrades the cluster and drastically diminishes unwinding activity. Thus, optimal function of nsp13 depends on a labile Fe-S cluster that is potentially targetable for COVID-19 treatment.

Synthesis and Pharmacological Evaluation of Novel Triazole-Pyrimidine Hybrids as Potential Neuroprotective and Anti-neuroinflammatory Agents.

OBJECTIVE: Neuroprotection is a precise target for the treatment of neurodegenerative diseases, ischemic stroke, and traumatic brain injury. Pyrimidine and its derivatives have been proven to use antiviral, anticancer, antioxidant, and antimicrobial activity prompting us to study the neuroprotection and anti-inflammatory activity of the triazole-pyrimidine hybrid on human microglia and neuronal cell model. METHODS: A series of novel triazole-pyrimidine-based compounds were designed, synthesized and characterized by mass spectra, 1HNMR, 13CNMR, and a single X-Ray diffraction analysis. Further, the neuroprotective, anti-neuroinflammatory activity was evaluated by cell viability assay (MTT), Elisa, qRT-PCR, western blotting, and molecular docking. RESULTS: The molecular results revealed that triazole-pyrimidine hybrid compounds have promising neuroprotective and anti-inflammatory properties. Among the 14 synthesized compounds, ZA3-ZA5, ZB2-ZB6, and intermediate S5 showed significant anti-neuroinflammatory properties through inhibition of nitric oxide (NO) and tumor necrosis factor-α (TNF-α) production in LPS-stimulated human microglia cells. From 14 compounds, six (ZA2 to ZA6 and intermediate S5) exhibited promising neuroprotective activity by reduced expression of the endoplasmic reticulum (ER) chaperone, BIP, and apoptosis marker cleaved caspase-3 in human neuronal cells. Also, a molecular docking study showed that lead compounds have favorable interaction with active residues of ATF4 and NF-kB proteins. CONCLUSION: The possible mechanism of action was observed through the inhibition of ER stress, apoptosis, and the NF-kB inflammatory pathway. Thus, our study strongly indicates that the novel scaffolds of triazole-pyrimidine-based compounds can potentially be developed as neuroprotective and anti-neuroinflammatory agents.

Modification of the 4Fe-4S Cluster Charge Transport Pathway Alters RNA Synthesis by Yeast DNA Primase.

DNA synthesis during replication begins with the generation of an ∼10-nucleotide primer by DNA primase. Primase contains a redox-active 4Fe-4S cluster in the C-terminal domain of the p58 subunit (p58C). The redox state of this 4Fe-4S cluster can be modulated via the transport of charge through the protein and the DNA substrate (redox switching); changes in the redox state of the cluster alter the ability of p58C to associate with its substrate. The efficiency of redox switching in p58C can be altered by mutating tyrosine residues that bridge the 4Fe-4S cluster and the nucleic acid binding site. Here, we report the effects of mutating bridging tyrosines to phenylalanines in yeast p58C. High-resolution crystal structures show that these mutations, even with six tyrosines simultaneously mutated, do not perturb the three-dimensional structure of the protein. In contrast, measurements of the electrochemical properties on DNA-modified electrodes of p58C containing multiple tyrosine to phenylalanine mutations reveal deficiencies in their ability to engage in DNA charge transport. Significantly, this loss of electrochemical activity correlates with decreased primase activity. While single-site mutants showed modest decreases in activity compared to that of the wild-type primase, the protein containing six mutations exhibited a 10-fold or greater decrease. Thus, many possible tyrosine-mediated pathways for charge transport in yeast p58C exist, but inhibiting these pathways together diminishes the ability of yeast primase to generate primers. These results support a model in which redox switching is essential for primase activity.

Ir(III) and Ru(II) Complexes in Photoredox Catalysis and Photodynamic Therapy: A New Paradigm towards Anticancer Applications.

Individually, photoredox catalysis (PC) and photodynamic therapy (PDT) are well-established concepts that have experienced a remarkable resurgence in recent years, leading to significant progress in organic synthesis for PC and clinical approval of anticancer drugs for PDT. But, very recently, new photoredox catalyst systems based on Ir(III) and Ru(II) complexes have garnered significant interest because they can simultaneously be used as PDT agents apart from their demonstrated PC activity. This highlight discusses the unique PC behavior of emerging Ir(III)- and Ru(II)-based systems while also examining their potential PDT activity in cancer treatment.

Co(II) complexes of curcumin and a ferrocene-based curcuminoid: a study on photo-induced antitumor activity.

Co(II) complexes having a ferrocene-based curcuminoid (Fc-curH) ligand viz. [Co(L)2(Fc-cur)]ClO4 (1, 2), where L is phenanthroline base, namely, 1,10-phenanthroline (phen in 1) and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 2) have been synthesized, characterized and evaluated as photochemotherapeutic agents in vitro. The corresponding Co(II) complexes of the naturally occurring polyphenol curcumin (curH), namely, [Co(L)2(cur)]ClO4 (3, 4), where L is phen (in 3) and dppz (in 4) were synthesized and their photo-induced anticancer activities compared with their ferrocene containing counterparts 1 and 2. The Co(II) acetylacetonato complex viz. [Co(phen)2(acac)]ClO4 (5) was structurally characterized through X-ray crystallography and used as control for cellular experiments. The Co(II) complexes having ferrocene-based curcuminoid are remarkably stable at physiological condition with higher lipophilicity compared to their curcumin analogues. The complexes display significant binding propensity to calf thymus (ct) DNA and human serum albumin (HSA). The complexes 1-4 display remarkable visible light induced cytotoxicity with the ferrocenyl analogues showing more phototoxic index (PI). The Co(II) curcumin complexes localize in the nucleus and mitochondria of A549 cells. The primary cell death mechanism is believed to be apoptotic in nature induced by light assisted generation of reactive oxygen species (ROS).Graphic abstract.

Novel triazole-sulfonamide bearing pyrimidine moieties with carbonic anhydrase inhibitory action: Design, synthesis, computational and enzyme inhibition studies.

A series of new triazole-sulfonamide bearing pyrimidine derivatives were designed and synthesized via click chemistry. All new compounds (SH-1 to SH-28) were validated by 1HNMR, 13CNMR, HRMS, and SH-3 was further structurally validated by X-Ray single diffraction study. These compounds (SH-1 to SH-28) were tested as inhibitors of human carbonic anhydrase (hCA) isoforms, such as hCA I, II, IX and XII, using a stopped flow CO2 hydrase assay. Most of the compounds exhibited significant inhibitory activity against hCA II and weak inhibitory activity against hCA I. The target compounds also displayed moderate to excellent inhibitory activity against tumor-related hCAs IX and XII. Some compounds, e.g., SH-20 (Ki = 9.4 nM), SH-26 (Ki = 1.8 nM) and SH-28 (Ki = 0.82 nM) exhibited excellent inhibitory activity and selectivity profile against hCAs XII over IX. SH-23 displayed promising inhibitory activity and selectivity profile against both tumor-related hCAs IX (Ki = 2.9 nM) as well as XII (Ki = 0.82 nM) over hCA I and II. To understand the molecular interactions, molecular docking study of compounds SH-20, SH-23, SH-26 and SH-28 with hCA XII and SH-23 also with hCA IX were performed. The computational study evidenced favorable interaction between the inhibitors and active residues of both proteins. Some of these derivatives are promising leads for the development of selective, anticancer agents based on CA inhibitors.

BODIPY based red emitters: Synthesis, computational and biological studies.

Donor-Acceptor type BODIPYs with strong absorption and fluorescence in the red region (550-800 nm) are reported. The aromatic groups like N-butylcarbazole/ N-butylphenothiazine/ benzothiadiazole were attached to the C-8 position of the BODIPY core with furan or thiophene spacers. TD-DFT studies indicated significant charge distribution between C-8 aromatic heterocycles and BODIPY core in all the molecules. The in-vitro studies of the N-butylcarbazole substituted BODIPYs indicated significant localization in the endoplasmic reticulum and lysosomes of the cancer cells. The BODIPYs showed decent cytotoxicity after 48 h incubation period (14.9 to 31.8 µM) in HeLa and A549 cancer cells, indicating their potential application as theranostic agents.

Synthesis of Water-Soluble Thioglycosylated trans-A2B2 Type Porphyrins: Cellular Uptake Studies and Photodynamic Efficiency.

The synthesis of water-soluble thioglycosylated A2B2 type porphyrins and their zinc(II) complexes is reported. The water-soluble trans-A2B2 porphyrins were synthesized in two steps, via [2+2] condensation between thioglycosylated dipyrromethanes and aromatic aldehydes in 15-21% yields. The thioglycosylated trans-A2B2 porphyrins showed decent in vitro singlet oxygen generation, which was supported by the intracellular DCFDA study. The in vitro cellular investigations of thioglycosylated A2B2 porphyrins were carried out in lung cancer cells (A549) to test their photodynamic therapeutic (PDT) activity. The PDT study revealed significant cytotoxicities of porphyrins with IC50 values between 23.3 and 44.2 µM in the dark, whereas, after visible light exposure, the photosensitizers exhibited IC50 values around 11.1-23.8 µM. The water-soluble thioglycosylated zinc(II) porphyrins having two meso-N-butylcarbazole groups exhibited an excellent degree of photocytotoxicity (IC50 = 4.6-8.8 µM). The flow cytometry analysis revealed that cellular uptake and ROS (reactive oxygen species) generation efficiency of water-soluble thioglycosylated zinc(II) porphyrins were considerably higher than nonmetalated porphyrins. Confocal microscopy images displayed substantial distribution in the endoplasmic reticulum with partial colocalization in mitochondria and lysosomes of water-soluble thioglycosylated zinc(II) porphyrins in A549 cells.

Anticancer properties, apoptosis and catecholase mimic activities of dinuclear cobalt(II) and copper(II) Schiff base complexes.

The present work describes coordination chemistry and biological evaluation of two novel dinuclear complexes [Co2(HL1)2(H2O)2]·8H2O (1) and [Cu2(L2)2] (2) obtained from the Schiff base ligands, H3L1 and H2L2 (formed in situ). The two complexes are characterized by single crystal X-ray, spectral and variable temperature magnetic and theoretical (DFT/TDDFT) analysis. X-ray analysis confirms both the complexes to be dinuclear with distorted octahedral and square pyramidal geometry around Co(II) and Cu(II) ions, respectively. Magnetic studies reveal presence of moderate ferromagnetic interactions in both the complexes with J = 98 (1) and 32 (2) cm-1. The magnetic interactions are further corroborated by DFT studies. Co(II) complex (1) exhibited enhanced catecholase activity with Kcat = 213.48 h-1, which is attributed to the greater extent of charge contribution on Co2+ as compared to Cu2+ as determined by DFT calculations. Furthermore, both the complexes show potent anticancer activity toward HeLa (cervical) and A549 (lung) cancer cell lines with IC50 = 6-7 µM at 48 h, which ascertains both the complexes as better anticancer drugs than cisplatin. Furthermore, 1 and 2 exhibit apoptosis of HeLa cells by demonstrating nuclear blebbings with shrinking morphology. Hence, the present complexes could be employed as a model for metalloenzymes as well as potential anticancer substituents of cisplatin in future course.

Naphthalene-triazolopyrimidine hybrid compounds as potential multifunctional anti-Alzheimer's agents.

In an attempt to construct potential anti-Alzheimer's agents Naphthalene-triazolopyrimidine hybrids were synthesized and screened in vitro against the two cholinesterases (ChE)s, amyloid ß aggregation and for antioxidation activity. Single-crystal X-ray crystallography was utilized for crystal structure determination of one of the compounds. In vitro study of compounds revealed that most of the compounds are capable of inhibiting acetylcholinesterase and Butyrylcholinesterase activity. Particularly, the compounds 4e and 4d exhibited IC50 values ranging from 8.6 to 14 nM against AChE lower than the standard drug Donepezil (IC50 49 nM). Best result was found for compound 4e with IC50 of 8.6 nM (for AChE) and 150 nM (for BuChE). Selectivity upto that of Donepezil and even more was observed for 4a, 4c and 4h. Investigation by electron microscopy, transmission electron microscopy and ThT fluorescence assay unveils the fact that synthesized hybrids exhibit amyloid ß self-aggregation inhibition. The compounds 4i and 4j revealed highest inhibitory potential, 85.46% and 72.77% at 50 µM respectively; above the standard Aß disaggregating agent, Curcumin. Their antioxidation profile was also analyzed. Studies from DPPH free radical scavenging assay and ORAC assay depicts molecules to possess low antioxidation profile. Results suggest that triazolopyrimidines are potential candidate for Acetylcholinesterase (AChE), Butyrylcholinesterase (BuChE), and amyloid ß aggregation inhibition. In silico ADMET profiling indicates drug-like properties with a very low toxic influence. Such synthesized compounds provide a strong vision for further development of potential anti-Alzheimer's agents.

Water soluble thioglycosylated BODIPYs for mitochondria targeted cytotoxicity.

The facile synthesis of water-soluble mitochondria targeting thioglycosylated BODIPYs is reported. Thioglycosylated BODIPYs were synthesized in 25-26% yields via thioglycosylated dipyrromethanes in four steps. The dipyrromethanes and thioglycosylated BODIPYs were characterized by various techniques including HRMS, NMR spectroscopy and X-ray crystallography. In-vitro cellular investigations in skin keratinocyte (HaCaT) and cervical (HeLa) cancer cells revealed significant cytotoxicities with IC50 values between 23.83 to 48.61 µM. The flow cytometry experiments revealed significant cellular uptake of thioglycosylated BODIPYs into HaCaT cells and thioglucosyl substituted BODIPY (9) showed higher cellular uptake and ROS generation than the rest of the molecules. The highlight of this study is the mitochondrial targeting by the neutral BODIPYs, as judged by the colocalization experiments using confocal microscopy.

Probing the antibacterial and anticancer potential of tryptamine based mixed ligand Schiff base Ruthenium(III) complexes.

Development of new chemotherapeutic agents to treat microbial infections and recurrent cancers is of pivotal importance. Metal based drugs particularly ruthenium complexes have the uniqueness and desired properties that make them suitable candidates for the search of potential chemotherapeutic agents. In this study, two mixed ligand Ru(III) complexes [Ru(Cl)2(SB)(Phen] (RC-1) and [Ru(Cl)2(SB)(Bipy)] (RC-2) were synthesised and characterized by elemental analysis, IR, UV-Vis, 1H, 13C NMR spectroscopic techniques and their molecular structure was confirmed by X-ray crystallography. Antibacterial activity evaluation against two Gram-positive (S. pneumonia and E. faecalis) and four Gram-negative strains (P. aurogenosa, K. pneumoniae, S. enterica, and E. coli) revealed their moderate antibacterial activity with MIC value of ≥250 µg/mL. Anticancer activity evaluation against a non-small lung cancer cell line (H1299) revealed the tremendous anticancer activity of these complexes which was further validated by DNA binding and docking results. DNA binding profile of the complexes studied by UV-Visible and fluorescence spectroscopy showed an intercalative binding mode with CT-DNA and an intrinsic binding constant in the range of 3.481-1.015× 105 M-1. Both the complexes were also found to exert weak toxicity to human erythrocytes by haemolytic assay compared to cisplatin. Potential of these complexes as anticancer agents will be further delineated by in vivo studies.

Pyriplatin-Boron-Dipyrromethene Conjugates for Imaging and Mitochondria-Targeted Photodynamic Therapy.

Monofunctional pyriplatin analogues cis-[Pt(NH3)2(L)Cl](NO3) (1-3) having boron-dipyrromethene (BODIPY) pendants (L) with 1,3,5,7-tetramethyl-8-(4-pyridyl)-4,4'-difluoroboradiazaindacene moieties were designed and synthesized, and their photocytotoxic properties were studied. The Pt-BODIPY conjugates displayed an absorption band within 505-550 nm and a green emissive band near 535 nm in 1% DMSO/DMEM (Dulbecco's modified Eagle's medium) buffer. Complex cis-[Pt(NH3)2(4-Me-py)Cl](NO3) (4) was used as a control for determining the structural aspects by X-ray crystallography. The mono- and diiodinated BODIPY complexes 2 and 3 showed generation of singlet oxygen on light activation as evidenced from the 1,3-diphenylisobenzofuran (DPBF) titration experiments. The cytotoxicity of the BODIPY complexes was tested against A549 (human lung cancer), MCF-7 (human breast cancer), and HaCaT (human skin keratinocyte) cells in dark and visible light (400-700 nm, 10 J cm-2). While complexes 2 and 3 showed excellent photocytotoxicity (IC50 ≈ 0.05 µM), they remained essentially nontoxic in the dark (IC50 > 100 µM). The emissive bands of 1 and 2 were used for cellular imaging by confocal microscopy study, which showed their mitochondrial localization. This was further supported by platinum estimation from isolated mitochondria and mitochondrial depolarization through a JC-1 assay. The photomediated apoptotic cell death was evidenced from flow cytometric assays, annexin-V/FITC-PI (fluorescein isothiocyanate-propidium iodide) and cell cycle arrest in sub-G1 and G2/M phases. The complexes bind to 9-ethylguanine as a model nucleobase to form monoadducts. A mechanistic study on DNA photocleavage activity using pUC19 DNA showed singlet oxygen as the reactive oxygen species (ROS). The combination of photodynamic therapy with DNA cross-linking property enhanced the anticancer potential of the monofunctional BODIPY-conjugates of pyriplatins.

Monofunctional BODIPY-Appended Imidazoplatin for Cellular Imaging and Mitochondria-Targeted Photocytotoxicity.

Monofunctional platinum(II) complexes of formulation cis-[Pt(NH3)2(L)Cl](NO3), where L is an imidazole base conjugated to 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) with emissive (L1 in 1) and nonemissive (L2 in 2) moieties were prepared and characterized, and their singlet oxygen-mediated photoinduced cytotoxicity was studied. The 1-methylimidazole (1-MeIm) complex 3 was prepared as a control and for structural characterization by X-ray crystallography. Complexes 1 and 2 showed strong visible absorption bands at 500 nm (ε = 2.7 × 104 M-1 cm-1) and 540 nm (1.4 × 104 M-1 cm-1). Complex 1 is emissive with a band at 510 nm (ΦF = 0.09) in 1% dimethyl sulfoxide/Dulbecco's Modified Eagle's Medium (pH 7.2). Singlet oxygen generation upon photoirradiation with visible light (400-700 nm) was evidenced from 1,3-diphenylisobenzofuran titration experiments showing significant photosensitizing ability of the BODIPY complexes. Both 1 and 2 were remarkably photocytotoxic in visible light (400-700 nm, 10 J cm-2) in skin keratinocyte HaCaT and breast cancer MCF-7 cells giving IC50 values in nanomolar concentration. The complexes were, however, essentially nontoxic to the cells in the dark (IC50 > 80 µM). Complex 2 having a diiodo-BODIPY unit is nonemissive but an efficient photosensitizer with high singlet oxygen generation ability in visible light (400-700 nm). Confocal microscopy using the emissive complex 1 showed significant mitochondrial localization of the complex. Cell death via apoptotic pathway was observed from the Annexin-V-FITC/PI assay. The formation of Pt-DNA adducts was evidenced from the binding experiments of the complexes 1 and 2 with 9-ethylguanine as a model nucleobase from 1H NMR and mass spectral studies.

Discovery of Quinolinone Hybrids as Dual Inhibitors of Acetylcholinesterase and Aß Aggregation for Alzheimer's Disease Therapy.

The development of multitargeted therapeutics has evolved as a promising strategy to identify efficient therapeutics for neurological disorders. We report herein new quinolinone hybrids as dual inhibitors of acetylcholinesterase (AChE) and Aß aggregation that function as multitargeted ligands for Alzheimer's disease. The quinoline hybrids (AM1-AM16) were screened for their ability to inhibit AChE, BACE1, amyloid fibrillation, α-syn aggregation, and tau aggregation. Among the tested compounds, AM5 and AM10 inhibited AChE activity by more than 80% at single-dose screening and possessed a remarkable ability to inhibit the fibrillation of Aß42 oligomers at 10 µM. In addition, dose-dependent screening of AM5 and AM10 was performed, giving half-maximal AChE inhibitory concentration (IC50) values of 1.29 ± 0.13 and 1.72 ± 0.18 µM, respectively. In addition, AM5 and AM10 demonstrated concentration-dependent inhibitory profiles for the aggregation of Aß42 oligomers with estimated IC50 values of 4.93 ± 0.8 and 1.42 ± 0.3 µM, respectively. Moreover, the neuroprotective properties of the lead compounds AM5 and AM10 were determined in SH-SY5Y cells incubated with Aß oligomers. This work would enable future research efforts aiming at the structural optimization of AM5 and AM10 to develop potent dual inhibitors of AChE and amyloid aggregation. Furthermore, the in vivo assay confirmed the antioxidant activity of compounds AM5 and AM10 through increasing GSH, CAT, and SOD activities that are responsible for scavenging the ROS and restoring its normal level. Blood investigation illustrated the protective activity of the two compounds against lead-induced neurotoxicity through retaining hematological and liver enzymes near normal levels. Finally, immunohistochemistry investigation revealed the inhibitory activity of ß-amyloid (Aß) aggregation.

Red light-activable biotinylated copper(II) complex-functionalized gold nanocomposite (Biotin-Cu@AuNP) towards targeted photodynamic therapy.

We report the synthesis and characterization of red-light activable gold nanoparticle functionalized with biotinylated copper(II) complex of general molecular formula, [Cu(L3)(L6)]-AuNPs (Biotin-Cu@AuNP), where L3 = N-(3-((E)-3,5-di-tert-butyl-2-hydroxybenzylideneamino)-4-hydroxyphenyl)-5-((3aS,4S,6aR)-2-oxo-hexahydro-1H-thieno[3,4-d]imidazol-4-yl)pentanamide, L6 = 5-(1,2-dithiolan-3-yl)-N-(1,10-phenanthrolin-5-yl)pentanamide, which was explored for their photophysical, theoretical and photo-cytotoxic potentials. The nanoconjugate exhibits differential uptake in biotin positive and biotin negative cancer cells as well as normal cells. The nanoconjugate also shows remarkable photodynamic activity against biotin positive A549 (IC50: 13 µg/mL in red light; >150 µg/mL in dark) and HaCaT (IC50: 23 µg/mL in red light; >150 µg/mL in dark) cells under red light (600-720 nm, 30 Jcm-2) irradiation, with significantly high photo-indices (PI>15). The nanoconjugate is less toxic to HEK293T (biotin negative) and HPL1D (normal) cells. Confocal microscopy confirms preferential mitochondrial and partly cytoplasmic localization of Biotin-Cu@AuNP in A549 cells. Several photo-physical and theoretical studies reveal the red light-assisted generation of singlet oxygen (1O2) (Ф (1O2) =0.68) as a reactive oxygen species (ROS) which results in remarkable oxidative stress and mitochondrial membrane damage, leading to caspase 3/7-dependent apoptosis of A549 cells. Overall, the nanocomposite (Biotin-Cu@AuNP) exhibiting red light-assisted targeted photodynamic activity has emerged as the ideal next generation PDT agents.

Identification, in-vitro anti-plasmodial assessment and docking studies of series of tetrahydrobenzothieno[2,3-d]pyrimidine-acetamide molecular hybrids as potential antimalarial agents.

Malaria is the most lethal parasitic infections in the world. To address the emergence of drug resistance to current antimalarials, here we report the design and synthesis of new series of tetrahydrobenzothieno[2,3-d]pyrimidine-acetamide hybrids by using multicomponent Petasis reaction as the key step and evaluated in vitro for their antimalarial effectiveness. The structure of all the compounds were confirmed by NMR Spectroscopy and mass spectrometry. Most of the compounds showed potent antimalarial activity against both CQ-sensitive (3D7) and CQ-resistant (W2) strains. A8, A5, and A4 are the most potent compounds that showed excellent anti-plasmodial activity against CQ-resistant strain in the nanomolar range with IC50 values 55.7 nM, 60.8 nM, and 68.0 nM respectively. To assess the parasite selectivity, the in vitro cytotoxicity of selected compounds (A3-A6, A8) was tested against HPL1D cells, demonstrating low cytotoxicity with high selectivity indices. Furthermore, these compounds were also evaluated on two additional human cancerous cell lines (A549 and MDA-MB-231), confirming their anticancer effectiveness. The in vitro hemolysis assay also showed the non-toxicity of these compounds on normal uninfected human RBCs. The interaction of these hybrids was also investigated by the molecular docking studies in the binding site of wild type Pf-DHFR-TS and quadruple mutant Pf-DHFR-TS. The in silico ADMET profiling also revealed promising physicochemical and pharmacokinetic parameters for the most active hybrids, which provide strong vision for further development of potential antimalarials.

Identification of new oxospiro chromane quinoline-carboxylate antimalarials that arrest parasite growth at ring stage.

Malaria still threatens half the globe population despite successful Artemisinin-based combination therapy. One of the reasons for our inability to eradicate malaria is the emergence of resistance to current antimalarials. Thus, there is a need to develop new antimalarials targeting Plasmodium proteins. The present study reported the design and synthesis of 4, 6 and 7-substituted quinoline-3-carboxylates 9(a-o) and carboxylic acids 10(a-b) for the inhibition of Plasmodium N-Myristoyltransferases (NMTs) using computational biology tools followed by chemical synthesis and functional analysis. The designed compounds exhibited a glide score of -9.241 to -6.960 kcal/mol for PvNMT and -7.538 kcal/mol for PfNMT model proteins. Development of the synthesized compounds was established via NMR, HRMS and single crystal X-ray diffraction study. The synthesized compounds were evaluated for their in vitro antimalarial efficacy against CQ-sensitive Pf3D7 and CQ-resistant PfINDO lines followed by cell toxicity evaluation. In silico results highlighted the compound ethyl 6-methyl-4-(naphthalen-2-yloxy)quinoline-3-carboxylate (9a) as a promising inhibitor with a glide score of -9.084 kcal/mol for PvNMT and -6.975 kcal/mol for PfNMT with IC50 values of 6.58 µM for Pf3D7 line. Furthermore, compounds 9n and 9o exhibited excellent anti-plasmodial activity (Pf3D7 IC50 = 3.96, 6.71 µM, and PfINDO IC50 = 6.38, 2.8 µM, respectively). The conformational stability of 9a with the active site of the target protein was analyzed through MD simulation and was found concordance with in vitro results. Thus, our study provides scaffolds for the development of potent antimalarials targeting both Plasmodium vivax and Plasmodium falciparum.Communicated by Ramaswamy H. Sarma.

Copper(ii) curcumin complexes for endoplasmic reticulum targeted photocytotoxicity.

Three copper(ii) complexes viz. [Cu(cur)(L)(ClO4)] (1-3), where Hcur is curcumin and L is 1,10-phenanthroline (phen, 1), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 2), or dipyrido[3,2-a:2',3'-c]phenazine (dppz, 3) were synthesized, fully characterized by various physicochemical methods and evaluated for their light-assisted chemotherapeutic potential. The complexes [Cu(acac)(L)(ClO4)] (4-6), where Hacac is acetylacetone and L is phen (in 4), dpq (in 5) and dppz (in 6), were synthesized and used as controls. The solid state structures of complexes 4 and 5 were determined by single crystal X-ray diffraction. The curcumin complexes (1-3) were redox inactive at the copper centre, whereas the acetylacetonato complexes (4-6) displayed a Cu(ii)/Cu(i) couple at ∼0.1 V vs. Ag/AgCl reference electrode in DMF. Complexes 1-3 showed an intense curcumin-based band at ∼440 nm in DMF-Tris-HCl buffer (pH = 7.2) (1 : 9 v/v) which masks the copper based d-d band. The complexes bind to human serum albumin (HSA) with moderate efficacy. They also displayed significant binding affinity for calf-thymus (CT) DNA. The lipophilic curcumin complexes show remarkable visible light induced cytotoxicity (IC50 = ∼4 µM) with high phototoxic indices (PI) with low dark toxicity in human cervical carcinoma (HeLa) and human lung carcinoma (A549) cells. The corresponding acetylacetonato controls (4-6) did not show significant cytotoxicity in the dark or light. DCFDA and annexin V-FITC/PI assays using flow cytometry confirm the induction of significant apoptosis in cancer cells via generation of cytotoxic reactive oxygen species upon photoactivation. Confocal microscopic images using complex 3 demonstrate localization of the complexes predominantly in the endoplasmic reticulum of HeLa cells.