Anti-inflammatory and analgesic activities of methanol extract of Helianthus annuus Linn. (Asteraceae) leaf

This study evaluate the anti-inflammatory and analgesic properties of Helianthus annuus Linn. in rats. Methanol extract of Helianthus annuus (HAE) leaf was used in this study. Formalin- and egg-albumin induced-paw edema were used to investigate the anti-inflammatory activities while acetic acid-induced writhing reflex and tail flick models were used to evaluate the analgesic properties. The doses of HAE used were 150, 300 and 600 mg/kg. Acetylsalicylic acid (ASA) was used as reference drug in the anti-inflammatory and writhing reflex models while pentazocine (reference drug) was used in tail flick model. The negative control was dosed 5% tween-20 (10 ml/kg). The HAE exhibited significant (P < 0.05) dose-dependent anti-inflammatory and analgesic activities. At 3 hour (h) post treatment, the HAE (300 mg/kg) produced 33.33% and 32.94% while ASA produced 36.36% and 35.29% reduction in paw volume in the formalin and egg-albumin induced paw edema models respectively when compared with negative control. In the acetic acid-induced writhing reflex, ASA and HAE (600 mg/kg) produced 67.89% and 35.78% reduction in the number of writhing, respectively when compared with the negative control. Pentazocine and HAE (300 mg/kg) caused 67.62% and 35.24% increase in pain reaction time when compared with the negative control. The study affirms the folkloric uses of Helianthus annuus in the management of pain and inflammation.