Unripe fruit of Annona muricata Linn. (Annonaceae) (soursop) is used in
traditional African medicine for the treatment of
neuralgia,
rheumatism, and arthritic
pain. This study sought to investigate the
analgesic and anti-inflammatory effects of lyophilized fruit extract of Annona muricata (AM) in rodents. The
analgesic activity was evaluated using the mouse writhing,
formalin, and hot-plate tests while the anti-inflammatory action was investigated using the
carrageenan-induced rat paw
edema and
xylene-induced ear
edema tests. Pretreatment with AM (50, 100, and 200 mg/kg, p.o.) produced dose-dependent (P<.001) inhibition of writhes and
formalin-induced
pain in the late phase. AM and
morphine produced time-course increase in pain threshold in hot-plate test. However, the
analgesic effect elicited by AM was reversed (P<.05) by
naloxone pretreatment. Similarly, the time-dependent increase in paw circumference induced by
carrageenan was inhibited by AM treatment with peak effect (0.23±0.10 cm; P<.001, 200 mg/kg; 6 h), which was comparatively similar to that of
diclofenac treated. Further, the
xylene-induced ear
edema was significantly reduced by AM (50 or 100 mg/kg) pretreatment; however, the anti-inflammatory effect elicited by AM was prevented by pretreatment of mice with N(G)-nitro-
l-arginine (20 mg/kg, i.p.,
nitric-oxide synthase inhibitor) 15 min before AM (200 mg/kg, p.o.). The in vitro
cyclooxygenase assay also showed that AM produced concentration-dependent inhibition of both
cyclooxygenase (COX)-1 and COX-2 activity by 39.44%±0.05% and 55.71%±0.12%, respectively, at 100 μg/mL. In conclusion, A. muricata possesses
analgesic effect through interaction with opioidergic pathway and anti-inflammatory property through inhibition of chemical
mediators of inflammation.