Potentiometric study on critical micellization concentrations (CMC) of sodium salts of bile acids and their amino acid derivatives

Abstract

The critical micellization concentration (CMC)s of a group of sodium salts of bile acids, i.e., cholic acid (abbreviated as C), deoxycholic acid (DC), chenodeoxycholic acid (CDC), ursodeoxycholic acid (UDC), glycocholic acid (GC), glycodeoxycholic acid (GDC), glycochenodeoxycholic acid (GCDC), and some amino acid derivatives of C and DC were determined by potentiometric titration. An automatic titration system has been established to determine the apparent dissociation constants of bile acids below and above CMC. The CMC's of these bile salts were in accord with those values obtained by conventional methods such as surface tension and/or cholesterol solubilization methods. The CMCs of amino acid derivatives of cholic, and deoxycholic acids were observed to be much lower than those of the respective free bile acids. The reasons of the difference were described.