Anti-inflammatory and Antinociceptive Effects of the Methanol Extract of Indigofera arrecta Hochst-Holl. in Rodents

Background: Indigofera arrecta (Hoscht-Holl) is used traditionally in Nigeria for treating conditions associated with pain and inflammation. Based on the traditional use of the plant for the management of pain and inflammation, the present study was designed to evaluate scientifically the anti-inflammatory and analgesic activities of whole plant parts of Indigofera arrecta so as to generate data that could support such traditional applications. To the best of our knowledge, no similar studies on Indigofera arrecta have been undertaken previously. Objectives: To experimentally demonstrate the anti-inflammatory and analgesic effects of the whole plant parts of Indigofera arrecta. Methodology: The extract of I. arrecta was screened for the presence of phytochemicals. The methanol extract of the plant was tested orally for acute toxicity effect (median lethal dose; LD50) at doses between 10 mg/kg and 5000 mg/kg. Similarly, the extract at 100, 400 and 1000 mg/kg was evaluated in vivo for anti-inflammatory and analgesic properties in rodent models. Results: Carbohydrates, cardiac glycosides, flavonoids, glycosides, saponins, steroids and triterpenes and tannins were detected in the extract. The extract is relatively safe when administered orally to rats with a median lethal dose (LD50) of ≥ 5000 mg/kg. The plant exhibited significant (p< 0.05) in vivo anti-inflammatory and analgesic effects at all the tested doses. However, at 100 mg/kg, the extract did not produce significant effect against thermal-induced pain. Discussion: Phytochemical study showed the presence of flavonoids, glycosides, tannins, steroids and triterpenes in the extracts of Indigofera arrecta. One or more of these constituents either singly or in combination may be responsible for the pharmacological action of the plant. Flavonoids and phenolic compounds have been reported to have multiple biological effects such as antioxidant, analgesic, anti-inflammatory actions, inhibition of platelet aggregation, inhibition of mast cell histamine release and inhibitory actions on arachidonic acid metabolism as demonstrated by in vitro and in vivo tests. Flavonoids have been documented to have anti-inflammatory and analgesic effects. The analgesic and anti-inflammatory effects of steroids and tannins have also been reported. Key words: Indigofera arrecta, Methanol extract, Antinociceptive, Analgesic, Median lethal dos