Piperin is the active compound of black pepper (Piper nigrum). From the piperine was obtained the molecule of the piperic acid (PAC). The objective of this study was to evaluate the antinociceptive and anti-inflammatory of the compound. The antinociceptive effects of PAC were evaluated by abdominal writhing, formalin, capsaicin and tail-flick tests; while the anti-inflammatory effects were evaluated by paw oedema and air pouch tests, and in vitro COX inhibition assay. The possible action mechanism of PAC was evaluated using naloxone, L-NAME, glibenclamide and atropine in tail flick test and by Cholinesterase activity assay and production of TNF-α and IL-1β. PAC significantly reduced the nociceptive effects induced by acetic acid or formalin in mice. PAC also demonstrated an antinociceptive effect in the tail-flick model. The muscarinic receptor antagonist, atropine reduced the antinociceptive effect of PAC in the tail-flick model. PAC was able to inhibit capsaicin-induced nociception, showing involvement of TRPV1. The compound did not alter the motor capacity of the animals, not interfering in the nociceptive response. PAC also showed anti- inflammatory activity by inhibiting the formation of carrageenan-induced paw oedema, leukocyte migration, and cytokine production / release. Atropine reduced the activity of PAC on leukocyte migration, and cytokine production. The compound showed to be able to reduce the cytokine production stimulated by capsaicin. PAC inhibited the COX activity. The results presented suggest that the possible cholinomimetic action and vanilloid agonist of the piperic acid may be responsible by antinociceptive and anti- inflammatory effects; these effects are devoid of toxicity.

Pain is responsible for inducing physical and mental stress, interfering negatively in patients' quality of life. Classic analgesic drugs, such as opioids and non‐steroidal anti‐inflammatory drugs, are known for their wide range of adverse effects, making it important to develop new drugs. Thus, this study aimed to analyse the action of the hybrid compound cis‐ (±) ‐acetate of 4‐chloro‐6‐ (naphthalene‐1‐yl) ‐tetrahydro‐2h‐pyran −2‐yl) methyl2‐ (2‐ [2,6‐dichlorophenylamine] phenyl (LS19) under acute nociceptive conditions, and deepened the understanding of the responsible mechanisms. Male Swiss mice were evaluated in the acetic acid‐induced abdominal writhing, formalin, tail flick, capsaicin‐ and glutamate‐induced nociception, thermal stimulation in animals injected with capsaicin and rotarod tests besides the acute and subchronic toxicological evaluation. The compound showed effect on the acetic acid‐induced abdominal writhing, formalin (both phases), tail flick, thermal stimulation in animals injected with capsaicin and capsaicin‐induced nociception tests. In the study of the mechanism of action was observed reversion of the antihyperalgesic effect of the compound from the previous intraperitoneal and intrathecal administration of naloxone, nor‐binaltorphimine, naltrindole, methylnaltrexone, 7‐nitroindazole, L‐NAME, ODQ, glibenclamide on the tail flick test. In the thermal stimulation in animals injected with capsaicin, the compound showed antinociceptive effect by oral and intraplantar routes, besides to reducing the levels of TNF‐α, IL‐1β and PGE2 in the paws previously administered with capsaicin. There were no signs of acute and subchronic intoxication with the compound. In summary, the compound LS19 presented spinal and local antihyperalgesic effect, demonstrating participation of the opioid/NO/cGMP/K+ ATP pathway and TRPV1 receptors and it demonstrated safety in its use in mice.

Evaluate the anti-inflammatory activity in vivo and in vitro of cis-(±)-acetate of 4-chloro-6-(naphtalene-1-yl)-tetrahydro-2H-pyran-2-yl) methyl 2-(2-(2,6-diclorofenylamine) phenyl (LS19). Male Swiss mice were analyzed in the paw edema, ear edema, and air pouch tests, and in vitro COX inhibition, cytotoxicity evaluation, and cytokine and nitric oxide determination tests. The compound showed effect on the carrageenan- and bradykinin-induced paw edema and capsaicin-induced ear edema tests. In addition, the compound was able to inhibit leukocyte migration to decrease the levels of the pro-inflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β) and to increase the levels of the anti-inflammatory cytokine IL-10. The compound was also able to reduce levels of TNF-α, IL-6, and nitric oxide in the RAW 264.7 cell line and to inhibit COX activity. LS19 did not induce any significant changes in the viability of RAW 264.7 cells, demonstrating safety for these cell lines. The compound LS19 did not reduce the production of gastric mucus and induced a smaller increase in the extent of gastric lesions than that developed by the administration of diclofenac. In summary, the new compound proved to be safer and it had additional mechanisms compared to diclofenac.