Mechanism of action of coumarin and silver(I)- coumarin complexes against the pathogenic yeast Candida albicans

The anti-fungal activity and mode of action of a range of silver(I)- coumarin complexes was examined. The most potent silver(I)- coumarin complexes, namely 7-hydroxycoumarin-3-carboxylatosilver(I), 6-hydroxycoumarin-3-carboxylatosilver(I) and 4-oxy-3-nitrocoumarinbis(1,10-phenanthroline)silver(I), had MIC80 values of between 69.1 and 4.6 M against the pathogenic yeast Candida albicans. These compounds also reduced respiration, lowered the ergosterol content of cells and increased the trans-membrane leakage of amino acids. A number of the complexes disrupted cytochrome synthesis in the cell and induced the appearance of morphological features consistent with cell death by apoptosis. These compounds appear to act by disrupting the synthesis of cytochromes which directly aVects the cell's ability to respire. A reduction in respiration leads to a depletion in ergosterol biosynthesis and a consequent disruption of the integrity of the cell membrane. Disruption of cytochrome biosynthesis may induce the onset of apoptosis which has been shown previously to be triggered by alteration in the location of cytochrome c. Silver(I)- coumarin complexes demonstrate good anti-fungal activity and manifest a mode of action distinct to that of the conventional azole and polyene drugs thus raising the possibility of their use when resistance to conventional drug has emerged or in combination with such drugs

Role of cell cycle events and apoptosis in mediating the anti-cancer activity of a silver(I) complex of 4-hydroxy-3-nitro-coumarin-bis(phenanthroline) in human malignant cancer cells.

The central objective of the current study was to investigate the potential in vitro anti-proliferative effect of 4-hydroxy-3-nitro-coumarin (hncH), and the mixed-ligand silver (I) complex of 4-oxy-3-nitro-coumarin-bis (phenanthroline), [Ag(hnc)(phen)2] using four human-derived model cell lines. In addition, selected mechanistic studies were carried out using the most sensitive of the four cell lines. Results obtained show that the complex could decrease the proliferation of all four cell lines including neoplastic renal and hepatic, namely A-498 and HepG2 cells, respectively, along with two non-neoplastic renal and hepatic cell lines, HK-2 and Chang, respectively. Furthermore, non-neoplastic hepatic cells (Chang) appeared to be less sensitive to the effect of the complex, but this effect was not replicated in the non-neoplastic renal (HK-2) cells. Based on IC50 values [Ag(hnc)(phen)2] was shown to be almost four times more potent than cisplatin, using HepG2 cells. In addition, the observed anti-proliferative effect was shown to be both dose- and time-dependent. Furthermore, the complex was shown to decrease DNA synthesis, but did not intercalate with it. Moreover, there was no evidence that P-glycoprotein-mediated multi-drug resistance was likely to decrease antiproliferative activity. Cytological stains, analysis of genomic DNA, and biochemical assays [caspase-3 and -9 and cleaved poly(ADP-ribose)-polymerase protein] showed that cell death appeared to result from apoptosis, with the possibility of secondary necrosis. Additionally, flow cytometric analysis showed that the complex functioned through an alteration in cell cycle progression. Taken together, [Ag(hnc)(phen)2] has been shown to be a more potent anti-proliferative agent than cisplatin, capable of altering key biochemical events leading to cell death. Additional mechanistic studies are underway to probe more fully its mechanism of action

A Constructor-Based Reachability Logic for Rewrite Theories

Reachability logic has been applied to K rewrite-rule-based language definitions as a language-generic logic of programs. It has been proved successful in verifying a wide range of sophisticated programs in conventional languages. Here we study how reachability logic can be made not just language-generic, but rewrite-theory-generic to make it available not just for conventional program verification, but also to verify rewriting-logic-based programs and distributed system designs. A theory-generic reachability logic is presented and proved sound for a wide class of rewrite theories. Particular attention is given to increasing the logic's automation by means of constructor-based semantic unification, matching, and satisfiability procedures. The relationships to Hoare logic and LTL are discussed, new methods for proving invariants of possibly never terminating distributed systems are developed, and experiments with a prototype implementation illustrating the new methods are presented.Partially supported by NSF Grants CNS 13-19109 and CNS 14-09416, and AFOSR Contract FA8750-11-2-0084.Ope

Generalized Rewrite Theories and Coherence Completion

A new notion of generalized rewrite theory suitable for symbolic reasoning and generalizing the standard notion is motivated and defined. Also, new requirements for symbolic executability of generalized rewrite theories that extend those for standard rewrite theories, including a generalized notion of coherence, are given. Finally, symbolic executability, including coherence, is both ensured and made available for a wide class of such theories by automatable theory transformations.Partially supported by by NRL under contract number N00173-17-1-G002.Ope

Revealing the Roles of Desolvation and Molecular Self-Assembly in Crystal Nucleation from Solution: Benzoic and p -Aminobenzoic Acids

There has been much recent interest in the role of solution chemistry and in particular the importance of molecular self-assembly in the nucleation of crystalline phases. Techniques such as FTIR and NMR have highlighted the existence of solution-phase dimers which in many cases mirror the structural synthons found in the resulting macroscopic crystals. However, there are no reported examples in which this new insight into the solution phase has been linked directly to the kinetics of crystal nucleation. Here for the first time, using a combination of solution FTIR, computational chemistry, and measured crystal nucleation rate data, such a link is demonstrated for p-aminobenzoic (PABA) and benzoic acids nucleating from polar and nonpolar solvents. Solute dimerization and desolvation are found to be rate-determining processes in the overall nucleation pathway

Sferična kristalizacija zdravilnih učinkovin

Spherical crystallization of drugs is the process of obtaining larger particles by agglomeration during crystallization. The most common techniques used to obtain such particles are spherical agglomeration and quasi-emulsion solvent diffusion. Ammonia diffusion systems and crystallo-co-agglomeration are extensions of these techniques. By controlling process parameters during crystallization, such as temperature, stirring rate, type and amount of solvents, or excipient selection, it is possible to control the formation of agglomerates and obtain spherical particles of the desired size, porosity, or hardness. Researchers have reported that the particles produced have improved micromeritic, physical, and mechanical properties, which make them suitable for direct compression. In some cases, when additional excipients are incorporated during spherical crystallization, biopharmaceutical parameters including the bioavailability of drugs can also be tailored.Sferična kristalizacija je postopek izdelave večjih delcev z aglomeracijo manjših med samo kristalizacijo. Najpogosteje uporabljeni tehniki za izdelavo takšnih delcev sta sferična aglomeracija in kvaziemulzija z difuzijo topila. Sistem z difuzijo amoniaka in kristalo-ko-aglomeracija sta razširitvi teh dveh metod. Z nadzorovanjem procesnih parametrov med kristalizacijo, kot sta temperatura in hitrost mešanja, z izbiro lastnosti in množine topil ter z izbiro pomožnih snovi, lahko vplivamo na nastanek aglomeratov in izdelamo sferične delce želenih velikosti, primerne poroznosti ali trdote. Raziskovalci poročajo, da imajo izdelani delci izboljšane pretočne lastnosti, izboljšane druge fizikalne in mehanske lastnosti zaradi česar so primerni za direktno tabletiranje. V nekaterih primerih lahko ob vgradnji ustreznih pomožnih snovi, ki jih dodamo med procesom sferične kristalizacije, izboljšamo tudi biofarmacevtske lastnosti zdravilnih učinkovin vključno s povečanjem biološke uporabnosti