Antinociceptive activity of Hypericum grandifolium Choisy in mice.

The present study investigated the antinociceptive activity of different extracts prepared from the aerial parts of blossom of Hypericum grandifolium Choisy-a species native to the Macaronesian Region-using the acetic acid-induced writhing, formalin and tail flick test in mice. Oral administration of methanol extract (500 and 1,000 mg/kg p.o.), the aqueous, butanol and chloroform fractions (500 mg/kg p.o.) as well as subfractions F2 and F3 (45 mg/kg p.o.) from the chloroform fraction significantly inhibited acetic acid-induced writhing, with values ranging from 28 to 50% of inhibition. The methanol extract (1,000 mg/kg p.o.) and chloroform fraction (500 mg/kg p.o.) significantly reduced both phases of formalin-induced pain (with inhibition values ranging from 18 to 53%), whereas subfraction F2 (45 mg/kg p.o.) significantly inhibited the late phase (30%). In the tail flick assay, only the chloroform fraction (500 mg/kg p.o.) significantly prolonged the tail flick response. Different constituents, such as flavonoids and benzophenone derivatives, could account for the effects observed. Taking together, the results indicate that Hypericum grandifolium Choisy possesses both peripheral and central antinociceptive activities in mice, suggesting an interesting therapeutic potential for this species in pain diseases.