Analgesic and anti-inflammatory activities of the n-butanol fraction of Vernonia glaberrima
The n-butanol leaf fraction of Vernonia glaberrima was evaluated for its toxicity, analgesic and anti-inflammatory effects. The leaves of V. glaberrima were collected, identified and extracted with methanol using maceration method and the resulting crude methanol extract was then partitioned using different solvents of increasing polarity (hexane, chloroform, ethyl acetate and n-butanol respectively). Preliminary phytochemical screening was conducted on the n-butanol fraction (BF) using standard procedures. The median lethal dose (LD50) of the fraction was determined using Lorke’s method and the analgesic effect was evaluated using acetic acid-induced writhing test in mice, while the anti-inflammatory activity was assessed using carrageenan-induced paw oedema in rats. Secondary metabolites including saponins, tannins, alkaloids, glycosides and flavonoids were found in the fraction. The LD50 of the fraction was 2154 mg/kg indicating the fraction to be moderately toxic. The fraction at 150 mg/kg exhibited 77.6 % inhibition of writhes, higher than the standard drug, piroxicam (10 mg/kg) which had 53.7 % inhibition. The n-butanol fraction at 150 and 250 mg/kg significantly inhibited the carrageenan-induced paw oedema at the 2nd and 4th hour, respectively, while there was no significant inhibition at 500 mg/kg of the fraction. The standard drug was only able to inhibit oedema at the 1st hour. The results showed the n-butanol fraction of V. glaberrima to possess significant analgesic and anti-inflammatory activities thereby validating its traditional use in the treatment of pain and inflammation.