Ipomoea pes-caprae (L.) R. Br (Convolvulaceae) relieved nociception and inflammation in mice - A topical herbal medicine against effects due to cnidarian venom-skin contact.

Ethnopharmacological Relevance: Ipomoea pes-caprae is known as bayhops, beach morning glory or goat's foot, and in Brazil as salsa-de-praia. Its leaves are used in worldwide folk medicine for the relief of jellyfish-stings symptoms. The literature only reports the neutralizing effects of nonpolar plant derived over jellyfish venoms, without validating the popular use or exploring the mechanism of action.

Aim Of The Study: This study aimed to evaluate and validate the topical effects of a semisolid containing hydroethanolic extract obtained from the aerial parts of I. pes-caprae using different models of paw- and ear-oedema and spontaneous nociception in mice, attempting to better understand the mechanism involved in its effect.

Materials And Methods: Leaf and stem of I. pes-caprae were extracted by ethanol 50% (v/v) and the soft-extract was incorporated in Hostacerin® cream base at 0.5%, 1.0% and 2% (w/w). The anti-hypersensitivity effects were evaluated by injecting the Physalia physalis venom into the right mice's hindpaw pre-treated either with the semisolid containing the I. pes-caprae extract or with the isolated majority compound 3,5-Di-O-caffeoylquinic acid (ISA). The topical anti-inflammatory activity was investigated using both preclinical models: paw oedema induced by trypsin, bradykinin (BK), histamine and carrageenan, and ear oedema induced by capsaicin. Additionally, the model of spontaneous nociception induced by trypsin and capsaicin were used to verify the topical antinociceptive activity.

Results: The animals pre-treated with the semisolid containing I. pes-caprae extract or with the intraplantar injection of the major component (ISA) had the mechanical hypersensitivity induced by P. physalis venom significantly reduced. Significant inhibition was also observed in paw-oedema induced by trypsin, histamine and BK, and in a less extent in carrageenan-induced paw oedema. Similar effect was observed in mice challenged to the capsaicin-induced ear-oedema. Besides the vascular effects, the extract interfered with leukocyte migration induced by histamine injection. Finally, the semisolid presented significant inhibition in trypsin- and capsaicin-induced spontaneous nociception.

Conclusions: The hydroethanolic extract of I. pes-caprae showed compliance with the topical popular use of the herbal product to relieve the symptoms evoked by the cnidarian venom-skin contact, such as neurogenic oedema and nociception. The extract components seem to interfere with the effects resulting from the TRPV1, BR and PAR-2 activation, once it interfered with painful-behaviour and oedema induced by capsaicin, BK and trypsin, pointing the histaminergic system as the main target, once it is an important mediator in the signalling pathway of the aforementioned receptors.