Antinociceptive effect from Ipomoea cairica extract.

Ipomoea cairica L. Sweet (Convolvulaceae) is used in Brazilian folk medicine for the treatment of rheumatism and inflammations. Ipomoea cairica ethanolic extract (100, 300, 1000 and 3000 mg/kg; per os) induced dose-dependent reduction of response in the formalin test inflammatory phase in mice. The same dose range did not modify neurogenic pain in formalin test, tail-flick reflex latency, carrageenan-induced paw edema, and Rota-Rod test motor performance. From the bio-active fraction 3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid were obtained. These compounds have been previously reported to have analgesic and antioxidative effects. A possible explanation for the antinociception is that somehow the compounds present in the extract reduced the release of pro-nociceptive mediators unrelated to carrageenan-induced edema, such as histamine. Interestingly, caffeoylquinic acid derivatives have been reported to inhibit histamine release on in vitro models. The isolated caffeoylquinic acids could explain, at least in part, the antinociceptive effect of Ipomoea cairica polar extract.