Antinociceptive and antioxidant effects of hydromethanolic extract of Bridelia micrantha stem bark

Objective: Bridelia micrantha is among the commonly used herbs in the traditional management of disease conditions. This study aimed to evaluate the antinociceptive and antioxidant effects of the hydromethanolic extract of B.micrantha stem bark. Methods: The acute oral toxicity of the extract was evaluated using up and down method. The antinociceptive effects of B.micrantha extract at the doses of 50, 100 and 200 mg/kg were investigated using acetic acid induced writhing reflex and tail flick method. The effect of B.micrantha on thiopentone induced narcosis was also investigated. The antioxidant effect of B.micrantha was investigated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) photometric assay. Results: The extract was well tolerated at the high dose (2000 mg/kg) used for the acute toxicity study. The extract produced a significant dose-dependent decrease in the mean number of abdominal constriction in the acetic acid induced writhing reflex when compared to the negative control. Both the extract (200 mg/kg) and paracetamol (400 mg/kg) produced 61.85 and 73.08% inhibition of writhing reflex, respectively. B.micrantha and pentazocine (3 mg/kg) caused significant increase in the pain reaction time in treated rats when compared to the negative control group in tail flick method. The pretreatment of the rats with B.micrantha at different doses increased the normal sleeping time of thiopentone from 69.33 ± 7.31 min to an average of 105.33 ± 11.88 min. The extract also produced concentration-dependent increase in percentage antioxidant activity in DPPH photometric assay. Conclusion: This study demonstrates that Bridelia micrantha possess potent antinociceptive and antioxidant activities which validate its use in folkloric medicine for this purpose.