Precipitation and 13C-NMR relaxation enhancement measurements of the interactions of bile acids with synthetic cationic bile acid derivatives, and with spin labelled fatty acids
✍ Scribed by David G. Reid; Kaushika Gajjar; Simon P. Robinson; Deirdre M.B. Hickey; G.Martin Benson; Claire Haynes; Paul D. Leeson; Caroline M. Whittaker
- Book ID
- 103041641
- Publisher
- Elsevier Science
- Year
- 1991
- Tongue
- English
- Weight
- 554 KB
- Volume
- 60
- Category
- Article
- ISSN
- 0009-3084
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✦ Synopsis
In an investigation of novel potential bile acid sequestrants, the affinities of the sodium salts of the glycine and taurine conjugates of naturally occurring bile acids (cholate, deoxycholate, chenodeoxycholate and lithocholate) for several cationic ammonium bile acid derivatives have been investigated by measurements of the extent to which the derivatives are able to precipitate the bile acids. This is roughly proportional to the lipophilicity of the interacting species. Thus, amino and ammonium derivatives of cholic acid do not precipitate taurocholate or glycocholate to any great extent, whereas ammonium derivatives of deoxycholate and lith~g'holate are much more effective. To complement the precipitation measurements, high resolution 13C-NMR has been applied to imcstigate the weaker interactions between the ammonium cholate derivative and glycocholate, glycodeoxycholate and glycochenodcoxycholate. Addition of either of the latter two bile acids to the cationic ammonium compound results in considerable broadening of the 13C resonances of both species, indicating the formation of relatively rigid structures. In addition, we have used T_, relaxation enhancement induced by spin-labelled fatty acids to examine the mechanism of interaction with bile acids of amphiphilic anions, g hich might compete with bile acids for rites on bile acid sequestrants. Low concentrations of 16-DOXY L-Stearate dramatically broaden the 13C-NMR resonances of deoxycholate carbons 19,18 and 7 in particular, while 5-DOXY L-Stearate exerts much less specific effects. These results have been incorporated into a snapshot model of bile acid-fatty acid interactions.