Antinociceptive and antiedematogenic effects of the aqueous extract of Hyptis pectinata leaves in experimental animals

The aqueous leaf extract of Hyptis pectinata (L.) Poit (Lamiaceae), popular ly known in Brazil as "sambaicata" or "canudinho" was tested for its antino ciceptive effects using the abdominal writhing, hot plate and formalin lest models, and for its aniedematogenic effects using the carrageenin and arac hidonic acid-induced rat paw edema. The aqueous extract of Hyptis pectinata administered orally at doses of 100, 200 and 400 mg/kg had a significant a ntinociceptive effect in the test of acetic acid-induced abdominal writhing , with 43, 51 and 54% reduction of writhes, respectively, compared to the c ontrol. An increase in hot-plate latency of 47 and 37.5% was also observed in animals receiving doses of 200 and 400 mg/kg, p.o. when placed on a hot plate. In the formalin test, doses of 200 and 400 mg/kg, p.o. had no signif icant effect during the first phase of the test (0-5 min), while the dose o f 200 mg/kg, p.o. reduced the nociceptive effect by 70% during the second p hase (20-25 min). At the dose of 600 mg/kg, p.o., the aqueous extract inhib ited carrageenin-induced rat paw edema by 34.1%, and the dose of 300 mg/kg administered intraperitoneally inhibited the rat paw edema induced by subpl antar injection of arachidonic acid by 32.8%. These results suggest that th e aqueous extract from the Hyptis pectinata leaves produces antiedematogeni c and antinociceptive effects. The antinocipetion observed with the hot-pla te test probably involves the participation of the opioid system. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.