A molecular dynamics study on opioid activities of biphalin molecule

Cyclic Biphalin Analogues Incorporating a Xylene Bridge: Synthesis, Characterization, and Biological Profile

In this work we enhanced the ring lipophilicity of biphalin introducing a xylene moiety, thus obtaining three cyclic regioisomers. Novel compounds have similar in vitro activity as the parent compound, but one of these (6a) shows a remarkable increase of in vivo antinociceptive effect. Nociception tests have disclosed its significant high potency and the more prolonged effect in eliciting analgesia, higher than that of biphalin and of the disulfide-bridge-containing analogue (7).

Antinociceptive profile of potent opioid peptide AM94, a fluorinated analogue of biphalin with non-hydrazine linker

AM94 is a fluorinated analog of biphalin with non-hydrazine linker that has an in vitro affinity for μ-opioid and δ-opioid receptors tenfold higher than biphalin. Furthermore, in vivo evaluation in rats showed that AM94 has in hot plate test - after both intracerebroventricular and intravenous administrations - a greater and more durable efficacy than biphalin. Here, the antinociceptive profile of AM94 is further evaluated by following two different administration routes, intrathecal and subcutaneous, and two different animal species, rats and mice. The analgesic potency of AM94 is compared with that of both the parent peptide biphalin and morphine. Results show that in rats (tail flick test) and in mice (formalin test), AM94 has a higher and more durable analgesic effect than biphalin after intrathecal and subcutaneous administrations. Conformational properties of biphalin and AM94 were also investigated by variable-temperature (1)H NMR and energy minimization.