Cholates/cholic acid derivatives

Steroidal frameworks have been much used in synthetic ion transport designs. Cholate oligomers synthesized from polyamines and cholic acid derivatives represent another class of ion transporters (Figure 12). These compounds, inspired by squalamine antibiotic, are also known as molecular umbrellas because of their amphomorphism. Depending on the polarity of the medium, the hydrophilic cholate faces are exposed or hidden to the surface of the umbrella. These compounds such as 22 are active sodium... 

Bile acids, which exist mainly as bile salts, are polar carboxylic acid derivatives of cholesterol that are important in the digestion of food, especially the solubilization of ingested fats. The Na and salts of glycocholic acid and tauro-cholic acid are the principal bile salts (Ligure 25.41). Glycocholate and tauro-cholate are conjugates of cholic acid with glycine and taurine, respectively. 

Hydroxylation. The 2)8-hydroxylated derivative of cholic acid, 2, 3a,7a,12a-tetrahydroxy-5i8-cholanate, was characterized as a minor component of gastric contents of neonates with duodenal atresia [202], Identification was facilitated by the availability of the authentic compound, arapaimic acid, which was isolated from bile of Arapaima gigas (Chapter 10) and was synthesized [204], This tetrol is also a minor urinary metabolite of cholate in patients with intrahepatic cholestasis [123]. A polar bile acid formulated as a 2,3,6,7-tetrol obtained from urine of healthy newborn infants [199] apparently differs from an unidentified urinary tetrol from patients with cholestasis [164],... 

The physical chemistry of micellar structure and formation has been reviewed extensively elsewhere[40,45-47], and is only briefly summarized. The concentration at which micellar aggregation of bile salts molecules occurs (critical micellar concentration, CMC) is affected by bile salt structure, pH, temperature and a variety of other factors. Conjugated bile salts have a higher CMC than the unconjugates, and the CMC for trihydroxycholanates (cholic acid) is higher than for the dihydroxy derivatives. Among the latter, deoxy-cholate forms micelles at a lower CMC than does chenodeoxycholate. 

Dual-responsive polymer-based systems have been also proposed. The design and synthesis of polymers containing cholic acid pendant groups has been reported. Random copolymers derived from 2-(metha-ctyloylo gr)ethyl cholate (MAECA) with polyethylene glycol methyl ether... 

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