Association of deoxycholic acid in organic solvents

The distribution of deoxycholic acid (I) between aqueous buffer and an organic phase consisting of isooctane-1-octanol (70:30, v/v) (System A) or isooctane-chloroform (80:20, v/v) (System B) was studied. The distribution isotherms suggested that I associates strongly in the organic Systems A and B unlike in pure 1-octanol. Therefore, a previous model, describing distribution of bile salts between 1-octanol and aqueous buffer, was modified to include association of I in the organic phases to describe distribution behavior. The treatment suggested that I exists as monomer and dimer in System A with a dimerization constant of 820 M-1. A model consisting of monomer-tetramer-hexamer in the organic phase best describes the data for System B. The data support the view that association in the organic phase is due to hydrogen bonding between bile acid molecules.