Evaluation of Methanol Extract of Argenome mexicana Aerial Part on Nociception, Inflammation and Gastrointestinal Motility

Argenome mexicana Linn. (Family: Papaveraceae) is traditionally used to relieve inflammatory and pain-related health conditions. It is also used as laxative. The intraperitoneal median lethal dose (LD50 ) of the methanol extract was determined in mice. The methanol extract of the plant was 50 evaluated for antinociceptive effect using acetic acid-induced writhing test in mice and formalin induced pain test in rats. Fresh egg albumin-induced oedema model was used to test for its antiinflammatory effect in rats while the gastrointestinal effect was tested using gastrointestinal motility (transit) model in mice. The intraperitoneal LD value in mice was calculated to be 894.4 50 mg/kg. The extract (75, 150 and 300 mg/kg i.p) significantly (p< 0.05) and dose-dependently inhibited acetic acid-induced pain with the values of 44.83%, 68.97% and 81.38% respectively. Acetyl salicylic acid (ASA; 150 mg/kg i.p) also significantly (p<0.05) inhibited pain with inhibitory value of 65.52%. The extract (75, 150 and 300 mg/kg i.p) significantly (p< 0.05) and dose-dependently inhibited the early phase of formalin-induced pain with values of 56.76%, 75.68% and 78.38% respectively. The extract at the same doses also inhibited the late phase of formalin-induced pain in a dose-dependent manner with the values of 39.51%, 55.56% and 74.08% respectively. The late phase inhibition was only significant (p<0.05) at the doses of 150 and 300 mg/kg i.p. The magnitude of pain inhibition by the extract was higher in the early phase. The extract (75, 150 and 300 mg/kg i.p) produced a dose-dependent inflammatory inhibition with percentages of 15.00 %, 25.00 % and 73.34% respectively. ASA (150 mg/kg i.p) produced 36.67% inhibition. The extract produced gastrointestinal movement inhibition of 54.70%, 55.47% and 73.32% respectively. The inhibition was significant (p < 0.005) only at 150 and 300 mg/kg i.p while atropine (0.1 mg/kg i.p) produced a significant (p < 0.05) inhibitory effect with percentage of 63.94%. The study provided scientific justification for the traditional use of A. mexicana in pain and inflammatory health conditions but did not justify its use as a laxative.