Phenylalanine Derivatives Enhancing Intestinal Absorption of Insulin in Mice

The adjuvant effect of N-acyl-L-and D-phenylalanine derivatives on intestinal absorption of insulin was investigated in normal mice. The correlation between the chemical structural properties of the N-acyl moiety and the absorption-promoting activity was estimated from the glucose concentrations and the insulin levels in the blood of mice after oral combined administration of insulin and adjuvant. The chemical structural properties of N-acyl-phenylalanine derivatives necessary for adjuvant effect on intestinal absorption of insulin were as follows. 1. An aromatic ring is present, separated by two atoms from the acyl carbonyl group. 2. Either of X or Y is oxygen or X-Y is a double bond in Fig.2. 3. The N-acyl moiety has small hydrophobic substituents, such as F, Cl, or Me at Rα, Rβ, Rη and has an appropriate hydrophilic-hydrophobic balance of the overall molecule. The use of these agents to enhance insulin absorption offers the possibility of a new approach to oral insulin therapy.