[Dmt1]DALDA analogues modified with tyrosine analogues at position 1

Analogues of [Dmt1]DALDA (H-Dmt-d-Arg-Phe-Lys-NH2; Dmt=2′,6′-dimethyltyrosine), a potent μ opioid agonist peptide with mitochondria-targeted antioxidant activity were prepared by replacing Dmt with various 2′,6′-dialkylated Tyr analogues, including 2′,4′,6′-trimethyltyrosine (Tmt), 2′-ethyl-6′-methyltyrosine (Emt), 2′-isopropyl-6′-methyltyrosine (Imt) and 2′,6′-diethyltyrosine (Det). All compounds were selective μ opioid agonists and the Tmt1-, Emt1 and Det1-analogues showed subnanomolar μ opioid receptor binding affinities. The Tmt1- and Emt1-analogues showed improved antioxidant activity compared to the Dmt1-parent peptide in the DPPH radical-scavenging capacity assay, and thus are of interest as drug candidates for neuropathic pain treatment.