Bile acids are well known natural surfactants able to modify the
per?meability of biological membranes. The logarithm of partition coefficient
between, tradi?tionally used, n-octanol and water is a measure of
lipophilicity as a predictor of solute membrane partitioning. The aim of this
work was to determine partition coefficients of bile acids in a mixture of
water and chloroform and dibutyl ether at different pH values and with
addition of different concentrations of sodium ions, and to examine the
influence of the structure of bile acid nucleus on measured partition
coefficients. Partition coefficients of three bile acid salts were determined
using shake-flask method and the concentration of bile acids was determined
after twelve hours of shaking at the room temperature in aqueous and organic
layer using reversed phase HPLC with DAD detector on 210 nm. For all three
analysed bile acid salts values of logP are lower in dibutyl ether than in
chloroform. At certain pH values, curves representing the dependence of
partition coeffi?cient on pH value intersect, and these are the pH values for
which partition coefficients are the same for both solvents. Increasing the
solution ionic strength, this intersection is shifted toward lower pH values.
It is found that, for both organic solvents, after the addition of hy?droxyl
group in the steroid nucleus (i.e. if the bile acid is less hydrophobic) the
value of logP falls, especially if more hydroxyl groups are present. With
chloroform as a solvent, system quickly comes to excess with electrolyte ions
than with dibutyl ether.
Supra-molecular Association and Polymorphic Behaviour In Systems Containing Bile Acid Salts