NUCLEAR-MAGNETIC-RESONANCE STUDIES OF CYCLODEXTRIN COMPLEXES OF LINOLEIC-ACID AND ARACHIDONIC-ACID

Structures of alpha and beta-cyclodextrin complexes of linoleic and arachidonic acids were investigated by detailed H-1 spin-lattice relaxation time (T1) measurements and one-dimensional difference nuclear Overhauser enhancement (NOE) studies. On the basis of the observed NOE proximities and T1 values, it is concluded that the carboxyl arms of both linoleic and arachidonic acids are present within the cyclodextrin cavity with double bonds partly exposed or buried. While the double bond at 9-10 in linoleic acid is buried, the one at 12-13 is exposed, the molecule from position 11 being present in an inclined position, with the methyl end pointing away from the cavity laterally. The double bond in arachidonic acid at position 5-6 is buried; the other at 8-9 lies exposed. While the carboxyl arm is present within the cavity, the methyl arm lies parallel to the carboxyl arm outside the cavity.