M. Eduarda M. Araújo

Mechanism of hydrolysis of substituted N-thiazolylcarbamate esters in OH- solutions

Substituted secondary N-thiazolylcarbamate esters and some tertiary N-methyl, N-thiazolyl carbamate esters have been synthesised and the mechanism of the OH- catalysed hydrolyses investigated. These proved to be E1cB and BAc2 respectively, and this behaviour was compared with that of other carbamates.

Chemical Variability of Two Essential Oils of Tunisian Rue: Ruta montana and Ruta chalepensis

Abstract: The genus Ruta includes some popular aromatic species of the flora of Tunisia, with important medicinal properties. They have been traditionally been used in the folk as herbal remedy medicine for the treatment of a variety of disorders. Information about the essential oil compositions of the Tunisian medicinal plant Ruta montana has not been reported. For this reason the objective of this study was to determine and compare the chemical composition of the essential oils of dried leaves and stems of the two principal Tunisian Ruta species: Ruta montana and Ruta chalepensis. Chemical analyses were performed by GC-MS assays. Essential oil yields was 0.66 %, its the same for all organs. For the chemical composition, independent of species and organs, the major compound for the 4 essential oil was the 2-undecanone. 1-nonene and 2-nonanone were the second major component in R. montana and R. chalepensis essntial oils.

Cytotoxicity of N-nitrosoguanidines in a breast cancer cell model: Citotoxicidade de N-nitrosoguanidinas num modelo celular de cancro da mama

Nitric oxide (NO) is a biologically important molecule with diverse functions in the human body. In recent years, there has been a growing interest in the potential use of NO donors in cancer therapy, since several studies have shown that the regulation of NO levels influences various pro or antitumor processes. The anticancer effects of NO donors have already been described in different in vitro and in vivo studies. The aim of this preliminary study was to evaluate the antitumor potential of two compounds of the N-nitrosoguanidines family, L1 (1-nitroso-1methyl-3-benzoylguanidine) and L2 (1-nitroso-1-methyl-3-tolylsulfonylguanidine). The compounds did not show significant in vitro cytotoxicity in the human breast cancer cell model MDA-MB-231. However, further studies will be needed to duly elucidate their antitumor potential. The use of other cancer cell models and the combination of L1 and L2 with radiotherapy or with chemotherapy agents may constitute interesting approaches for future studies.

Hydrolysis of aryl N-methyl-N-arylsulfonylcarbamates

Tertiary sulfonylcarbamates 1 were prepared by reaction of a sulfonamide anion with aryl chloroformates. These previously unreported compounds hydrolyse in aqueous media to the parent sulfonamide and phenol. The pH–rate profile shows both spontaneous and base-catalysed processes. The reaction is also catalysed by buffers. Kinetic data for the hydrolysis of these compounds by HO− are best interpreted in terms of a mechanism involving rate-limiting formation of a tetrahedral intermediate from nucleophilic attack of hydroxide ion at the carbamate carbonyl carbon atom. For the 4-nitrophenylsulfonyl compound 1h decomposition of the tetrahedral intermediate appears to be rate-limiting with the sulfonamide anion, rather than the phenoxide, functioning as the leaving group. The buffer-catalysed process is consistent with general base-catalysed attack of water at the carbamate carbonyl carbon atom.