The herb known as bitter leaf (Vernonia amygdalina) is a shrub or small tree that can reach 23 feet in height when fully grown. Bitter leaf has a grey or brown coloured bark, which has a rough texture and is flaked. The herb is an indigenous African plant; which grows in most parts of sub-Saharan Africa. The East African country of Tanzania is traditionally linked to this plant and can be found growing wild along the edges of agricultural fields. It is a medicinal plant and fresh bitter leaf is of great importance in human diet because of the presence of vitamins and mineral salts. The aim of this study is to evaluate the anti-inflammatory and analgesic activities of the aqueous extract of Vernonia amygdalina in experimental animal models hence confirming its folkloric use.
Forty healthy white Wister strain albino rats (100–200g) and forty mice (15–30g) of either sex bred in the experimental animal house of the Faculty of Veterinary Medicine, University of Ibadan, Nigeria were used for the study. The forty rats were used for anti-inflammatory study while forty mice used for the analgesic study. In anti-inflammatory study, carrageenan and histamine-induced paw oedema were used while acetic acid-induced writhing test and formalin-induced paw lick test were deployed for analgesic test. Anti-oxidant activities of the plant on the other hand were assessed using ABTS, DPPH, FRAP and total phenolics test.
The aqueous leaf extract (ALE) was prepared by dissolving ground plant materials (200g) in 1 L of distilled water for 48 h, filtered, lyophilized and then used for the pharmacological investigations. Standard phytochemical methods were used to test for the presence of phytoactive compounds in the plant. Acute toxicity was carried out in mice to determine safe doses for use. The anti-inflammatory activities were conducted using carrageenan and histamine to induce oedema in rats while analgesic activities were embarked upon using acetic acid- induced writhing test and formalin-induced paw lick test. The anti-oxidant activities were assessed in vitro using ABTS, DPPH, FRAP and total polyphenolics.
The extract in doses of 100 and 200 mg/kg at 3 hr showed 10.1 and 37.3% inhibition of histamine induced-paw oedema respectively while indomethacin caused 38.3% inhibition at the same period. In the case of carrageenan induced paw oedema, the extract in doses of 100 and 200 mg/kg at 4 hr showed 43.8 and 60.1% inhibition respectively while indomethacin caused 54.5% inhibition. In the acetic acid- induced writhing test, the extract showed a good analgesic activity characterized by a significant reduction in the number of writhes with 100 and 200 mg/kg doses used when compared to the control group. The result was also similar to the formalin-induced paw lick test. The extract also showed good anti-oxidant activities with ABTS exhibiting a higher radical scavenging ability.