Daniela Ionescu

A tentative quantitative structure-toxicity relationship study of benzodiazepine drugs.

Benzodiazepines belong to a large family of drugs, being used as hypnotics, anxiolytics, tranquillizers, anticonvulsants, in pre-medication and intravenous sedation. Several quantitative structure-toxicity (lethal oral dose for mouse) relationship (QSTR) models for 54 benzodiazepine derivatives have been developed. The molecular structure of these compounds was energetically optimized by molecular mechanics calculations. To the lowest energy conformations thus obtained, quantum chemical calculations (RM1 approach) were applied to finally optimize the structures. Several structural descriptors, volumes, molecular surface area, hydrophobicities and quantum chemical descriptors were calculated from the minimized structures. Multiple linear regression (MLR) combined with genetic algorithm for variable selection, artificial neural networks (ANNs), support vector machines (SVMs) and partial least squares (PLS) have been employed. Few satisfactory MLR models with predictive power were obtained. Nonlinear modelling methods of ANNs and SVMs gave somewhat better models than those obtained by MLR using same set of descriptors. Additional information on the factors which influence the benzodiazepine toxicity was given by PLS. The obtained models can be used for a rough evaluation of benzodiazepine toxicity.

The Hydractinia echinata test-system. III: Structure-toxicity relationship study of some azo-, azo-anilide, and diazonium salt derivatives.

Structure-toxicity relationships for a series of 75 azo and azo-anilide dyes and five diazonium salts were developed using Hydractinia echinata (H. echinata) as model species. In addition, based on these relationships, predictions for 58 other azo-dyes were made. The experimental results showed that the measured effectiveness Mlog(1/MRC50) does not depend on the number of azo groups or the ones corresponding to metobolites, but it is influenced by the number of anilide groups, as well as by the substituents’ positions within molecules. The conformational analysis pointed out the intramolecular hydrogen bonds, especially the simple tautomerization of quinoidic (STOH) or aminoidic (STNH2) type. The effectiveness is strongly influenced by the “push-pull” electronic effect, specific to two hydroxy or amino groups separated by an azo moiety (double alternate tautomery, (DAT), to the –COOH or –SO3H groups which are located in ortho or para position with respect to the azo group. The levels of the lipophylic/hydrophilic, electronic and steric equilibriums, pointed out by the Mlog(1/MRC50) values, enabled the calculation of their average values Clog(1/MRC50) (“Köln model”), characteristic to one derivative class (class isotoxicity). The azo group reduction and the hydrolysis of the amido/peptidic group are two concurrent enzymatic reactions, which occur with different reaction rates and mechanisms. The products of the partial biodegradation are aromatic amines. No additive or synergic effects are noticed among them.

Influence of emulsifiers on the characteristics of polyurethane structures used as drug carrier

BackgroundEmulsifiers have a significant role in the emulsion polymerization by reducing the interfacial tension thus increasing the stability of colloidal dispersions of polymer nanostructures. This study evaluates the impact of four emulsifiers on the characteristics of polyurethane hollow structures used as drug delivery system.ResultsPolyurethane (PU) structures with high stability and sizes ranging from nano- to micro-scale were obtained by interfacial polyaddition combined with spontaneous emulsification. The pH of PU aqueous solutions (0.1% w/w) was slightly acidic, which is acceptable for products intended to be used on human skin. Agglomerated structures with irregular shapes were observed by scanning electron microscopy. The synthesized structures have melting points between 245-265°C and reveal promising results in different evaluations (TEWL, mexametry) on murine skin.ConclusionsIn this study hollow PU structures of reduced noxiousness were synthesized, their size and stability being influenced by emulsifiers. Such structures could be used in the pharmaceutical field as future drug delivery systems.