Acid dissociation and metal complex formation constants of penicillamine, cysteine, and antiarthritic gold complexes at simulated biological conditions 

 -  Journal of Pharmaceutical Sciences, 68(4), p.426-432, 1979 .
<br/><br/> Ionization constants for acid functions of D-penicillamine, L-cysteine, thiomalic acid, and thioglucose were measured by pH titration at 37° and 0.15 M ionic strength. Chelate formation constants for these ligands with calcium(II), iron(III), and gold(I)were then determined under the same conditions chosen to approximate the in vivo situation. Only iron(III)formed both 1:1 and 1:2 chelates with D-penicillamine, L-cysteine, and thiomalate; calcium formed weak and gold strong 1:1 complexes with all ligands studied. Because of precipitate formation, the stability constants for the systems thioglucose-iron(III), D-penicillamine-gold(I), and L-cysteine-gold(l)had to be determined indirectly with thiomalic acid as the competing ligand. The in vivo fate of antiarthritic gold(I)compounds remained uncertain, but gold(I)chelates probably persist as such for extended periods. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>AUROTHIOGLUCOSE<br/>AUROTHIOMALATE<br/>CALCIUM<br/>CHELATE<br/>CYSTEINE<br/>GOLD<br/>IRON<br/>LEAD<br/>MERCURY<br/>PENICILLAMINE<br/>THIOGLUCOSE<br/>THIOMALIC ACID