ABSTRACT
I. INTRODUCTION Bile salts as biosurfactants frequently have been developed as solubilizers, emulsifiers, and dispersion agents for water-insoluble substances in many fields such as cosmetics, medicinals, and chemicals. Many papers and reviews concerning the colloidal and surface properties of aqueous solutions of bile salts have been published. These bile salts show common colloidal and surface properties; they have bulky, hydrophobic steroidal rings and one carboxyl group at the end of an alkyl chain (R) on a position 17 carbon atom of a ring in the molecule (Fig. I); but their properties depend remarkably on the number and configuration of hydroxyl groups bound to the ring, which are different from those of ordinary surfactants with a linear hydrocarbon chain. The main bile salts are listed in order of increasing numbers of and by the position of the hydroxyl groups together with kinds of alkyl chains (R) and animal sources in Table 1 [1].
