Physicochemical properties of bile acids and their relationship to biological properties: an overview of the problem (original) (raw)

1984, Journal of Lipid Research

The structure of the bile acid molecule is described and correlated with physicochemical properties of bile acids such as solubility, ionization, and micelle formation. Recent measurements of the critical micellar concentration (CMC) of a large number of bile acids indicate that the CMC is influenced by both side chain and nuclear structure. Bile acids with hydroxy substituents on both sides of the steroid nucleus are non-amphipathic and do not form micelles, and decreasing the length of the side chain causes an exponential increase in the CMC. Bile acid ionization, measured by titration in alcoholwater mixtures, is shown to be uninfluenced by nuclear substituents; the pK, of all unconjugated bile acids is about 5. lnteractions of bile acid solutions with Ca4+ are discussed; A bit of history Supplemcntuy key words critical micellar concentration cholanoids Twenty-five years ago, the field of bile acids ("cholanology") was in its youth, although studies on bile and bile acids had been a continuing area of activity in chemical (1, 2), biochemical (3, 4), physiological (5), on the relationship between the physicochemica~ prop-Abbreviations: CMC, critical micellar concentration; CMT, critical micellar temperature; CMpH, critical micellar pH; OWDR, octanolerties and the properties Of acids* That water distribution ratio; HPLC, high performance liquid chromatogsuch a relationship does exist has become a working raphy.