Cyclic enkephalin and dermorphin analogues containing a carbonyl bridge

Area of Science:

• Medicinal Chemistry
• Peptide Chemistry
• Pharmacology

Background:

• Enkephalins and dermorphins are endogenous opioid peptides with analgesic properties.
• Cyclic peptide analogues can offer improved stability and receptor selectivity.
• Urea-based cyclization provides a novel method for peptide scaffold construction.

Purpose of the Study:

• To synthesize novel cyclic enkephalin and dermorphin analogues using urea linkage.
• To evaluate the biological activity of these cyclic peptides in guinea-pig ileum (GPI) and mouse vas deferens (MVD) assays.
• To investigate the structure-activity relationships by correlating conformational data with observed biological effects.

Main Methods:

• Synthesis of four cyclic enkephalin and four cyclic dermorphin analogues via urea bond formation.
• Pharmacological evaluation using guinea-pig ileum (GPI) and mouse vas deferens (MVD) bioassays.
• Conformational analysis using Nuclear Magnetic Resonance (NMR) spectroscopy and the EDMC method.

Main Results:

• Synthesized cyclic peptides exhibited diverse activities in GPI and MVD assays.
• Activity was dependent on the size of the cyclic ring and the position of the urea linkage.
• Conformational studies revealed distinct structures for high- and low-activity dermorphin analogues.

Conclusions:

• Cyclization strategy and structural features significantly impact the biological activity of enkephalin and dermorphin analogues.
• NMR and EDMC analyses provide insights into the conformational basis of peptide activity.
• These findings contribute to the design of novel peptide-based therapeutics.