Abstract
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.
Highlights
The importance of azo derivatives is due to broad range of applications, which practically cover all human activities, both as dyes [1] and pigments [2]
Mlog(MRC50) measured values and Clog(MRC50) (Microsoft Office Excel 2003) based on the experimental data/algorithm according to which +/− 0,50 log.u differences characterize the xenobiotics with identical toxicity
The accuracy of experimental data was checked by the standard deviations, which were determined by the Excel 2003 program
Summary
The importance of azo derivatives is due to broad range of applications, which practically cover all human activities, both as dyes [1] and pigments [2]. In the medical-pharmaceutics field, the use of azo-derivatives is of interest to assess the permeability of the blood-brain barrier (BBB) to macromolecules [3]. Several affections, such as Prion-, Alzheimer’s-, Chorea major- or Parkinson’s diseases, are due to protein misfolding and aggregation (amiloide) processes [4]. The coplanarity of the dye molecule allows an extended conjugation of the π-electrons of the azo group, –N=N– and of the aromatic nucleus with the p electrons of some +M effect auxochromes (–OH, –OR, –NH2, –NR2) or of some –M effect antiauxochromes (–NO2, –COOH, –SO3H) [6]
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