Synthesis, structure and toxicity evaluation of ethanolamine nitro/chloronitrobenzoates: a combined experimental and theoretical study

BACKGROUND

Nitroaromatic and chloronitroaromatic compounds have been a subject of great interest in industry and recently in medical-pharmaceutic field. 2-Chloro-4-nitro/2-chloro-5-nitrobenzoic acids and 4-nitrobenzoic acid are promising new agents for the treatment of main infectious killing diseases in the world: immunodeficiency diseases and tuberculosis.

RESULTS

New ethanolamine nitro/chloronitrobenzoates were synthesized and characterized by X-ray crystallography, UV-vis, FT-IR and elementary analysis techniques. The toxicity of the compounds prepared and correspondent components was evaluated using Hydractinia echinata as test system. A significant lower toxicity was observed for nitro-derivative compared with chloronitro-derivatives and individual components. Crystallographic studies, together with the chemical reactivity and stability profiles resulted from density functional theory and ab initio molecular orbital calculations, explain the particular behavior of ethanolamine 4-nitrobenzoate in biological test.

CONCLUSIONS

The experimental and theoretical data reveal the potential of these compounds to contribute to the design of new active pharmaceutical ingredients with lower 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 (ST_OH) or aminoidic (ST_NH2) 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.

Hydractinia echinata test system. II. SAR toxicity study of some anilide derivatives of Naphthol-AS type

In this paper, a toxicity study for a series of anilides of Naphthol-AS type is presented. The toxicity of the model compounds was determined by using the Hydractinia echinata (Hydrozoa) test system. Conformational analysis of Naphthol-AS derivatives was performed to elucidate the possible enzymatic hydrolysis mechanism of these compounds. This mechanism occurs with different rates and always leads to a stoichiometric mixture of reaction products, consisting in the substituted amine and the corresponding α-hydroxy-carboxylic acid. With one exception, the toxicities of the reaction products are subadditive. Quite similar measured toxicity values, log(1/MRC₅₀), led to their average calculated values, and thus to the establishment of class isotoxicity. This method represents a practical alternative useful for the reduction of experimental tests on animals to the lowest possible level, in accordance to the '3Rs' (reduction, refinement and replacement) concept.

SAR for Amine Salts of Carboxylic Acids to Hydractinia echinata

The relationship between the structure and biological activity (toxicity) SAR of the stoichiometric mixtures between anion and cation (or neutral species) proceeded at pH 8.2 from the different amine salts of benzoic, acetic, oxalic, naphthalene carboxylic acids was determined. Their toxicity was determined by using the metamorphosis (transformation) process of the marine invertebrate Hydractinia echinata (Hydrozoa, Cnidaria) from the freely swimming larva to a sessile polyp as a biological test system. The two components of the stoichiometric mixture, the anion and the cation or neutral species react independently, but in a parallel way, the effectiveness of the cation/neutral species being superior. The studied compounds were grouped by their cationic/neutral structure and measured toxicity. All of these series were also characterized by a calculated mean value of the toxicity. The marine organism, Hydractinia echinata was a good and advantageous alternative for the toxicity testing systems with vertebrate.