Phytochemical Analysis, Analgesic and Anti-inflammatory Studies on the n-Hexane Soluble Fraction of Vernonia glaberrima

Abstract

Vernonia species have been used in the management of pain and other ailments in traditional medicine. This study was aimed at investigating the phytochemical constituents, toxicity, analgesic and anti-inflammatory activities of the n-hexane soluble fraction of Vernonia glaberrima. Preliminary phytochemical screening of the n-hexane fraction revealed the presence of steroids and triterpenes while the intraperitoneal LD₅₀ of the fraction using Lorke’s method was 2154 mg/kg indicating the fraction to be slightly toxic. The analgesic property of the fraction was assessed using acetic acid-induced writhing test in mice and formalin-induced pain in rats while the anti-inflammatory effect was evaluated using formalin test in rats. The results of the study showed that the n-hexane fraction at the highest dose (500 mg/kg) decreased writhing response with 89.55 % inhibition. The fraction also exhibited significant (P<0.05) analgesic effect at both phases in the formalin test; the n-hexane fraction (250 and 500 mg/kg) and the standard drug, pentazocine (10 mg/kg) were able to significantly inhibit both phase while the extract 150 mg/kg diminished the pain induced by formalin in the first phase only. There was significant inhibition of oedema induced by carrageenan at the 1^st hour (150 mg/kg) and the 4^th hour at the graded doses of the fraction and the standard drug, piroxicam (10 mg/kg). The findings of this research suggests that the n-hexane soluble fraction of V. glaberrima contains bioactive constituents with analgesic and anti-inflammatory effect and thus, validates the use of the plant in the management of pain and inflammation in traditional medicine.