Davorka Završnik

Benzylidene-bis-(4-Hydroxycoumarin) and Benzopyrano-Coumarin Derivatives: Synthesis, 1H/13C-NMR Conformational and X-ray Crystal Structure Studies and In Vitro Antiviral Activity Evaluations

We report on the synthesis of 4-hydroxycoumarin dimers 1–15 bearing an aryl substituent on the central linker and fused benzopyranocoumarin derivatives 16–20 and on their in vitro broad anti-DNA and RNA virus activity evaluations. The chemical identities and structure of compounds 1–20 were deduced from their homo- and heteronuclear NMR measurements whereas the conformational properties of 5, 14 and 20 were assessed by the use of 1D difference NOE enhancements. Unequivocal proof of the stereostructure of compounds 7, 9, 16 and 18 was obtained by single crystal X-ray diffraction method. The X-ray crystal structure analysis revealed that two 4-hydroxycoumarin moieties in the 4-trifluoromethylphenyl- and 2-nitrophenyl derivatives (compounds 7 and 9, respectively) are intramolecularly hydrogen-bonded between hydroxyl and carbonyl oxygen atoms. Consequently, the compounds 7 and 9 adopt conformations in which two 4-hydroxy-coumarin moieties are anti-disposed. Antiviral activity evaluation results indicated that the 4-bromobenzylidene derivative of bis-(4-hydroxycoumarin) (compound 3) possesses inhibitory activity against HSV-1 (KOS), HSV-2 (G), vaccinia virus and HSV-1 TK- KOS (ACVr) at a concentration of 9–12 μM and at a minimum cytotoxic concentration (MCC) greater than 20 μM. Compounds 4–6, 8, and 20 were active against feline herpes virus (50% effective concentration, EC50 = 5–8.1 μM), that is at a 4-7-fold lower concentration than the MCC.

C-5 Hydroxyethyl and Hydroxypropyl Acyclonucleosides as Substrates for Thymidine Kinase of Herpes Simplex Virus Type 1 (HSV-1 TK): Syntheses and Biological Evaluation

The efficient syntheses of 5-(2-hydroxyethyl)- and 5-(3-hydroxypropyl)-substituted pyrimidine derivatives bearing 2,3-dihydroxypropyl, acyclovir-, ganciclovir- and penciclovir-like side chains are reported. A synthetic approach that included the alkylation of an N-anionic-5-substituted pyrimidine intermediate (method A) provided the target acyclonucleosides in significantly higher overall yields in comparison to those obtained by method B using sylilation reaction. The phosphorylation assays of novel compounds as potential substrates for thymidine kinase of herpes simplex virus type 1 (HSV-1 TK) showed that solely pyrimidine 5-substituted acyclonucleosides with a penciclovir-like side chain acted as a fraudulent substrates of HSV-1 TK. Moreover, the uracil derivative with penciclovir-like side chain with less bulky 2-hydroxyethyl substituent at C-5 proved to be a better substrate than the corresponding one with a 3-hydroxypropyl substituent. Therefore, this acyclonucleoside was selected as a lead compound for the development of a positron emission tomography HSV-1 TK activity imaging agent.

Artificial Neural Network and Docking Study in Design and Synthesis of Xanthenes as Antimicrobial Agents

The aim of the study was to investigate the efficiency of artificial neural networks and docking studies in prediction of antimicrobial activity for new compounds. For that purpose, two multilayer neural networks with feedforward architecture were developed. Also, docking studies were performed to investigate the hypothetical binding mode of the target compounds. A series of 2,2,5,5-tetramethyl-9-aryl-3,4,5,6,7,9-hexahydro-1H-xanthen-1,8(2H)-dione derivatives have been previously synthesized, characterized and evaluated for in vitro antimicrobial activity against Escherichia coli and Candida albicans strains. By comparing results of in vitro investigation, new 2,2,5,5-tetramethyl-9-(3,5-dibromophenyl)-3,4,5,6,7,9-hexahydro-1H-xanthen-1,8(2H)-dione possessed better antimicrobial activity against tested microorganisms than previously synthesized derivatives and these results also correlated well with results of docking studies.

Cytogenotoxicity of Inclusion Complexes of Diazepam with 2-Hydroxypropyl-β-cyclodextrin

Background Diazepam, as one of the most frequent prescribed drug from 1,4-benzodiazepine group, has certain limitations in pharmaceutical technology due to its poor solubility in water. By forming inclusion complexes with 2-hydroxypropyl-β-cyclodextrin, diazepams biopharmaceutical properties can be greatly improved. Aim Aim of this research was to in vitro evaluate genotoxicity of prepared novel complexes of diazepam and their influence on proliferation of human peripheral blood lymphocytes. Methods For identification of possible genotoxicity of diazepam inclusion complexes, cytokinesis-block micronucleus assay has been chosen. Evaluated concentrations of two diazepam inclusion complexes were 0.2 µg/mL, 0.5 µg/mL and 1.0 µg/mL in cell culture. For a reference, in vitro cytogenotoxicity evaluation of diazepam alone has been conducted as well. Results Neither one of the diazepam, complexed nor non-complexed, in given concentrations showed genotoxicity, induced genetic damage or loss of genetic material. Conclusions Nuclear division index values, as indicators of cytostaticity and cytotoxicity suggested that investigated inclusion diazepam complexes induced accelerated proliferation of human peripheral blood lymphocytes in vitro, therefore possibly shortening the duration and dynamics of the cell cycle.

UV/VIS absorption and fluorescence spectroscopic study of some 3‐substituted derivatives of 4‐hydroxycoumarin

Purpose – The purpose of this paper is to test absorption characteristics of some newly synthesised 4‐hidroxycoumarins, containing phenyl‐prop‐2‐enoyl group at the 3‐position. Change in spectral characteristics in solvents of different polarity (chloroform and acetonitrile) was followed in regard to the influence of the substitution at the phenyl ring and influence of concentration H+ ions. Effectiveness of tested substances was compared with well‐known UV absorbers such as benzophenone‐3 and butyl methoxydibenzoylmethane (BMDM).Design/methodology/approach – All the tested substances were dissolved in chloroform and acetonitrile, with 10‐3 mmol concentration range. The pH was adjusted using 0.1 mol/l HCl, glacial acetic acid, 0.1 mol/l NaOH (aqueous solution) and 0.1 mol/l NaOH (methanolic solution). Spectrophotometric measurement was recorded in the range of 200‐800 nm, using 1‐cm quartz cells.Findings – The tested 4‐hydroxycoumarin derivatives showed good UV absorption properties in the range 280‐380 nm...