Relative absorption of tryptophan ethyl ester amide derivatives with various fatty acid chains in the dog

Sandoz compound 57-118 is a mixture of tryptophan ethyl ester amide derivatives (analogues I-V) possessing one of five fatty acid chains which differ in chain length, configuration, or the degree of unsaturation. The relative absorption of each of the five analogues was investigated in the dog following single oral doses of the homologous mixture containing one 14C labelled analogue. It was shown that the extent of absorption of analogue I and its trans-isomer, II, both with a mono-unsaturated fatty acid chain, were similar. An additional double bond in the fatty acid moiety (analogue III) facilitated gastrointestinal absorption. On the other hand, saturated fatty acid chains appeared to render the molecule less efficiently absorbed; the extent of absorption being dependent on the chain length. Thus, analogue V with 16 carbon atoms on the fatty acid chain was better absorbed than IV with 18.