In vivo assessment of analgesic, antipyretic and anti-inflammatory effects of combined aqueous crude leaf extract of <I>Senna occidentalis</I> Linn. and <I>Vernonia amygdalina</I> Delile in rodents

Background: Pain is a significant global health burden. The side effects of the medications used currently to treat pain are quite serious—combination therapy guards against side effects and the development of resistance. Nigerians utilise Senna occidentalis and Vernonia amygdalina as traditional medicines for various illnesses. It has been noted that each plant has the potential to be analgesic, antipyretic, and anti-inflammatory. Thus this study evaluates the analgesic, antipyretic, and anti-inflammatory impact of the combined aqueous leaf extract of these plants. Methods: The formalin-induced paw-licking test, the acetic acid-induced writhing test in mice, and the tail flick model test in rats were used to evaluate analgesic effectiveness. Rats' paw oedema caused by carrageenan was used to investigate the anti-inflammatory effect, while rabbits' pyrexia caused by Escherichia coli endotoxin was used to assess the antipyretic action. Results: The combined effects of the extract exhibited a significant (p<0.01) inhibition of acetic acid- induced writhing. It also showed a significant (p<0.05) reduction in time spent licking the paw in the 0 – 5 min, although the greatest significance (p<0.01) was seen with the 400 mg/kg dose. However, in the 15 – 30 min, there was a reduction in time spent licking the paw and this was completely abolished by 200 mg/kg. In the tail-flick test, the combined effects of the extract showed a significant (p<0.001) increase in tolerance time at the 2nd, 3rd, and 4th hour. The combined aqueous leaf extracts (200 mg/kg) produced significant (p<0.05) anti-inflammatory effects at the 30 min in the carrageenan model. In Escherichia coli endotoxin-induced pyrexia test in rabbits, the combined effect of the extract (400th mg/kg, oral) exhibited a significant (p<0.05) reduction in the rectal temperature at the 60 min. Conclusion: This study showed that S. occidentalis and V. amygdalina combined aqueous leaf extract possesses significant analgesic and antipyretic activities. However, there is no significant anti-inflammatory activity. Further studies are warranted to elucidate the mechanism by which the combined extract exerts these effects.