Background: Hemorphins are endogenous hemoglobin-derived peptides that belong to
the family of “atypical” opioid peptides with both affinities to opioid receptors and ability to release
other endogenous opioid peptides.
Objective: In the present study, peptide analogues of Valorphin (VV-hemorphin-5) containing amino
phosphonate moiety synthesized by solid-phase peptide synthesis (Fmoc-strategy) were investigated
for their potential antinociceptive activities and compared to the reference VV-H in formalin-
induced model of acute and inflammatory pain in mice.
Methods: The hemorphin analogues were prepared by replacement of the one and/or two N-terminal
Val in VV-hemorphin5 (VV-H) with ((dimethoxy phosphoryl) methyl)-L-valine and
((dimethoxy phosphoryl) methyl)-L-leucine to obtain the compounds pVV-H, pL-H, and pLV-H.
Aiming to additionally prove the importance of amino acid valine, we introduced the ((dimethoxy
phosphoryl) methyl)-L-leucine to the N-side of VV-hemorphin-5 (pLVV-H). The experiments
were carried out on adult male ICR mice. All peptides were administered intracerebroventricularly
at three doses (50, 25 and 12,5 μg/mouse). We have studied the effects of the peptides on acute (1st
phase) and inflammatory (2nd phase) pain reaction using un experimental model with intraplantar
Results: VV-H showed a significant antinociceptive effect both in the acute and inflammatory phases
of the test. Although Valorphin hexa-, hepta-, and octapeptide analogs demonstrated a significant
antinociceptive effect, they showed substantial differences considering their effective dose and
the phase of the test as compared to the Valorphin.
Discussion: Data showed that modified heptapeptides pVV-H and pLV-H exerted the same or better
antinociception in acute and inflammatory pain, in comparison to the reference peptide, while
pL-H and pLVV-H analogues were less effective.
Conclusion: Our study contributes to the elucidation of the role of Valine and the number of amino
acid residues in the structure of hemorphin peptide analogs in their effectiveness in suppressing
both acute and inflammatory experimental pain.