INTERACTION OF BETA-CYCLODEXTRIN WITH BILE-ACIDS AND THEIR COMPETITION WITH VITAMIN-A AND VITAMIN-D3 AS DETERMINED BY H-1-NMR SPECTROMETRY

The interaction of beta-cyclodextrin (beta-CD) with four bile acids, c holic, taurocholic, chenodeoxycholic and lithocholic, was demonstrated by proton-NMR spectroscopy. Lithocholic and chenodeoxycholic acids ex hibit a stronger affinity for beta-CD than cholic and taurocholic acid s. The affinity of bile acids for beta-CD increases in relation to the ir hydrophobicity. The competition between these bile acids and the li pophilic vitamins A and D3 in the formation of beta-CD inclusion compl exes was studied. These vitamins compete with cholic and taurocholic a cids whereas they do not with lithocholic and chenodeoxycholic acids. In the latter case all of the beta-CD present was consumed by the bile acids with the vitamins remaining free in the medium. The affinity of vitamins A and D3 for beta-CD is lower than that of the bile acids. T herefore, when lithocholic or chenodeoxycholic acids are present, the formation of beta-CD inclusion complexes with the vitamins does not oc cur. The results of this study suggest that depletion of lipophilic vi tamins will not occur upon ingestion of beta-CD, thus providing furthe r support for the safety and suitability of beta-CD as an ingredient i n foods and orally administered drugs.