Antinociceptive Effect of Ethanolic Extract of Hybanthus enneaspermus Leaf in Rats

Aims: To test the hypothesis that Hybanthus enneaspermus leaf has an antinociceptive effect.
Methodology: Seventy-two male rats were randomly divided in a blinded fashion into 4 groups each for the tail immersion test (n=12 per group) and formalin test (n=6 per group). Group 1 (control) received 0.6 ml of distilled water. Group 2 received 100 mg/kg of acetaminophen (paracetamol). Group 3 and 4 received 500 mg/kg and 1000 mg/kg of ethanolic extract of Hybanthus enneaspermus leaf (EEHE) respectively.
Results: In the formalin test, oral administration of 500 mg/kg and 1000 mg/kg EEHE caused inhibitions of 62.48% and 72% in the early phase and 70.54% and 78.63% in the late phase respectively. The 1000 mg/kg dose significantly reduced the paw licking time when compared to the standard drug (acetaminophen) in the formalin test. The 500 mg/kg and 1000 mg/kg doses significantly increased the tail flick latency in a manner comparable to acetaminophen.
Conclusion: This study showed that the leaf has an anti-nociceptive effect.