Chelation in metal intoxication XLVI: synthesis of some alpha-mercapto-beta-substituted aryl acrylic acids and their in vitro cadmium chelating ability.

Objective: To synthesize some new alpha-mercapto-beta-substituted aryl acrylic acids, characterize them and investigate their in vitro cadmium chelating ability.
Methods: Six alpha-mercapto-beta-substituted aryl acrylic acids were prepared by the alkaline hydrolysis of 5- (aryl methylene) rhodanines, obtained from the condensation of substituted aldehydes and rhodanine following the reported procedure. The new compounds were characterized by elemental analysis, infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The liver and kidney from cadmium chloride pre-administered rats were homogenized and their nuclear mitochondrial fraction (NMF) and supernatant cytosol fraction (SCF) were separated. A measured volume of each fraction was dialyzed separately using "dialysis sack" against buffered-KCl medium containing a compound in the final concentration of 1 x 10(-3) mol/L for 3 h at 37 degrees C. The whole content of "sack" was subjected to cadmium estimation following digestion with conc. Nitric acid was detected using flame atomic absorption spectrometer.
Results: The in vitro screening showed that alpha-mercapto-beta-(p-methoxyphenyl) acrylic acid (compound 2) and alpha-mercapto-beta-(m-methoxy, p-hydroxyphenyl) acrylic acid (compound 4) were more effective than alpha-mercapto-beta-thienyl acrylic acid (compound 1) and alpha-mercapto-beta-(p-dimethylaminophenyl) acrylic acid (compound 3) in mobilizing cadmium as their dialyzable chelates. The presence of a methoxy group on the phenyl moiety (compounds 2 and 4) increases the metal chelating ability of mercapto acrylic acids.
Conclusions: Compounds 2 and 4 seem to have accessibility to the cellular system and capability of chelating-out the intracellularly bound cadmium.