Cyclic enkephalin analogs containing a cystine bridge

摘要: Abstract Two conformationally constrained enkephalin analogs were synthesized by substitution of cysteines in positions 2 and 5 oxidative disulfide bond formation. In the guinea pig ileum assay obtained cyclic analogs, [D-Cys -L-Cys ]enkephalinamide -D-Cys ]enkephalinamide, showed potency ratios 37.9 ± 0.8 73.3 0.9, respectively, relative to [Met ]enkephalin. The extremely high was shown be a consequence conformational restrictions introduced cyclization. Rat brain membrane binding studies with [ 3 H]naloxone H](D-Ala , D-Leu )enkephalin as radiolabels revealed moderate preference both for μ-receptors over δ-receptors. Furthermore, cystine-containing highly resistant enzymatic degradation.