Analgesic effects of the ethanolic extract from Magnolia ovata (Magnoliaceae) trunk bark and of N-acetylxylopine, a semi-synthetic analogue of xylopine

This study investigated the antinociceptive effects of the ethanolic extract (EEMO) obtained from Magnolia ovata (A.St.-Hil.) Spreng and N-acetylxylopine (AXyl), a stable derivative of xylopine in different models of nociception. The EEMO and AXyl inhibited the nociception induced by acetic acid in mice, in a dose-dependent manner with a maximal inhibition of 91 ± 9% and 50 ± 11%, respectively. Oral administration of EEMO or AXyl also significantly inhibited the inflammatory phase of formalin-induced nociception with maximal reduction of 87 ± 3.9% and 71 ± 10%, respectively. Confirming the effectiveness of the extract and the isolated compound in inflammatory responses, EEMO or AXyl inhibited carrageenan-induced mechanical allodynia with percentage of inhibition of 40 ± 6% for EEMO and 82 ± 8% for AXyl. Intraplantar injection of AXyl in the ipsilateral paw, but not in the contralateral paw, also reduced carrageenan-induced mechanical allodynia in mice. The response of the animals for maximal doses tested of EEMO and AXyl in the hot-plate or rota-rod models were not altered. These results show that the extract from M. ovata and the stable derivative AXyl possess analgesic properties towards inflammatory pain acting on peripheral sites.