Potent antinociceptive activity of a hydroalcoholic extract of Phyllanthus corcovadensis

This study analyses the analgesic effect of a hydroalcoholic extract (HE) from Phyllanthus corcovadensis in several models of pain in mice. HE (3-60 mg kg-1, i.p.) or (100-500 mg kg-1, p.o.) caused a graded and potent analgesic effect against the abdominal constriction response caused by acetic acid and acetylcholine with an ID50 of about 3 and 100 mg kg-1, respectively. In the tail-flick model HE (up to 500 mg kg-1, p.o.) was without effect, while morphine (1-10 mg kg-1, s.c.) caused a graded increase in pain latency (ID50, 3 mg kg-1). HE (1-300 mg kg-1) given both intraperitoneally and orally caused a potent and graded inhibition of the second phase of formalin-induced persistent pain in mice with an ID50 of 1 and 80 mg kg-1, respectively. In contrast, morphine (1-5 mg kg-1, s.c.) inhibited both phases of formalin-induced pain with an ID50 of 2.5 mg kg-1. Indomethacin (1-10 mg kg-1, i.p.) only inhibited the second phase of formalin-induced pain with an ID50 of about 3 mg kg-1. The analgesic effect of indomethacin, but not that caused by morphine and HE was accompanied by a graded inhibition of formalin-induced mouse paw oedema. In addition, HE up to 1 g kg-1 failed to prevent carrageenan- and dextran-induced rat hindpaw oedema. It is concluded that HE exhibits a potent antinociceptive profile, either when given intraperitoneally or orally.(ABSTRACT TRUNCATED AT 250 WORDS)