POTENT ANTINOCICEPTIVE ACTIVITY OF A HYDROALCOHOLIC EXTRACT OF PHYLLANTHUS-CORCOVADENSIS

This study analyses the analgesic effect of a hydroalcoholic extract (E-IE) 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 bath 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. The mechanisms that underly its analgesic effect are unclear at present, but appear to be unrelated to inhibition of synthesis of arachidonic acid via cyclo-oxygenase or to activation of opioid receptors.