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Emodin (1,3,8-trihydroxy-6-methyl-anthraquinone) is a natural secondary plant product, originally isolated from the rhizomes of Rheum palmatum. Many reports show its diuretic, vasorelaxant, antibacterial, antiviral, anti-ulcerogenic, immunosuppressive, hepatoprotective, anti-inflammatory and anticancer potential. Emodin is a pleiotropic molecule capable of interacting with several major molecular targets, e.g. NF-κB, AKT/mTOR and STAT3. The compound can also act as an inhibitor of some protein kinases, with special affinity to protein kinase CK2. The aim of the presented report was to evaluate antifungal properties of emodin and its activity towards CK2 isolated from Candida cells. Our studies revealed that the compound suppressed growth of the cells of reference strains as well as clinical Candida strains, with minimal inhibitory concentration and minimal fungicidal concentration values between 12.5 and 200 μg/mL. Moreover, at a low concentration, the compound was able to effectively stop hyphal formation, thus showing a distinct antivirulent potential. Interestingly, we showed that emodin added to Candida culture inhibited the phosphorylation of many cellular proteins, presumably owing to the inhibition of protein kinase CK2. Notably, the enzyme isolated from the Candida cells was susceptible to emodin with IC of 2.8 μg/mL. Indeed, our computational modelling revealed that emodin was able to occupy the ATP-binding pocket of CK2. Copyright © 2017 John Wiley & Sons, Ltd.

A new series of coumarin-1,2,3-triazole conjugates with varied alkyl, phenyl and heterocycle moieties at C-4 of the triazole nucleus were synthesized using a copper(I)-catalysed Huisgen 1,3-dipolar cycloaddition reaction of corresponding O-propargylated coumarin (3) or N-propargylated coumarin (6) with alkyl or aryl azides. Based on their minimal inhibitory concentrations (MICs) against selected microorganisms, six out of twenty-six compounds showed significant antibacterial activity towards Enterococcus faecalis (MIC = 12.5–50 µg/mL). Moreover, the synthesized triazoles show relatively low toxicity against human erythrocytes.

A new naphthoquinone-based chemosensor 2-((3hydroxyphenyl)amino)-3-(phenylthio)naphthalene-1,4-dione (2HPN) was successfully synthesized for the selective detection of Fe 2+ . The sensing property of the chemosensor 2HPN was evaluated in aqueous acetonitrile (CH 3 CN) medium by a fluorescence emission method. The metal-binding studies of the ligand 2HPN showed selective "turn-on" fluorescence responses for Fe 2+ (K a = 1.0 × 10 6 M −1 ). The detection limit of the ligand 2HPN to Fe 2+ was calculated to be 0.272 μM, which is lower than the World Health Organization recommendation (0.3 mg/L) in drinking water. The most significant feature of the obtained chemosensor 2HPN is its ability to sense Fe 2+ via naked-eye detection over various metal ions. The chemosensor operated via the intramolecular charge transfer effect, which was supported by Fourier transform infrared analysis, NMR titrations, and quantum chemical calculations. The efficiency of the chemosensor 2HPN as a biomarker for Fe 2+ was successfully proven by imaging in human cancer cells and zebrafish. Thus, the chemosensor 2HPN could be a useful biomarker for the precise sensing of Fe 2+ in clinical diagnosis.

A simple naphthoquinone−dopamine hybrid (2CND) was designed and fabricated as a colorimetric and fluorescence chemosensor for the selective recognition of Sn 2+ in the aqueous medium. This simply accessible chemosensor was prepared by connecting of naphthoquinone acceptor and dopamine donor moieties via Michael-like addition reaction. The chemosensor 2CND showed a turn-on fluorescence response which operated through the inhibited photoinduced electron transfer effect. The sensor probe shows remarkable performance, such as high selectivity, sensitivity, excellent water solubility, and rapid response to Sn 2+ (less than 5 s). The detection mechanism of the 2CND−Sn 2+ complex was supported by FT-IR analysis, 1 H NMR titration, and DFT calculations. Besides, the 1:1 binding stoichiometry was confirmed by the ESI-MS spectral analysis. Furthermore, the chemosensor 2CND has been successfully employed as a fluorescence probe to monitor trace Sn 2+ in live cells and zebrafish. The sensor probe 2CND could serve as an effective fluorescence bioimaging probe for the discriminative detection of diseased and normal human cells.

1,4‐Naphthoquinones are an important class of compounds present in a number of natural products. In this study, a new series of 1,4‐naphthoquinone derivatives were synthesized. All the synthesized compounds were tested for in vitro antimicrobial activity. In this present investigation, two Gram‐positive and five Gram‐negative bacterial strains and one pathogenic yeast strain were used to determine the antibacterial activity. Naphthoquinones tested for its antibacterial potencies, among seven of them displayed better antimicrobial activity against Staphylococcus aureus ( S. aureus ; 30–70 μg/mL). Some of the tested compounds showed moderate to low antimicrobial activity against Pseudomonas aeruginosa ( P. aeruginosa ) and Salmonella bongori ( S. bongori ; 70–150 μg/mL). In addition, most active compounds against S. aureus were evaluated for toxicity to human blood cells using a hemolysis assay. For better understanding, reactive oxygen species (ROS) generation, time‐kill kinetic study, and apoptosis, necrosis responses were investigated for three representative compounds.

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