Phytochemical screening, safety evaluation, anti-inflammatory and analgesic studies of the leaf extracts of Lannea welwitschii
The analgesic and anti-inflammatory activities of the leaves of Lannea welwitschii (Anacardiaceae)using different organic solvent for its extraction was investigated in this study because the plant is used in Traditional African Medicine (TAM) to treat swellings, oedema, gout and diarrhoea.
Phytochemical screening of the powdered leaves was carried out while graded concentrations of the solvent extracts were prepared and used for the study. Pilot toxicity was carried out to determine safe dose using acute toxicity study, haematology and serum chemistry as indices of toxicity. Thereafter anti-inflammatory and analgesic studies were conducted using standard tests such as carrageenan, histamine-induced-oedema, tail flick test and acetic acid writhing test. Phytochemical screening of the powdered material showed that tannin, flavonoid and reducing sugar were present while alkaloids, cardiac glycosides, saponins and anthraquinones were absent. In the pilot toxicity study using the aqueous extract of the plant, no mortality was recorded even though the animals treated with 3000mg/kg showed slight dullness after 48 hours. In terms of haematological and biochemical parameters examined in this study, no significant changes were observed. While chloroform extract caused significant reduction in histamine-induced oedema, the n-hexane, ethyl acetate and methanol extract did not. In the carrageenan test, none of the extract caused any significant reduction while in the writhing test the effects of the extracts were less than that of indomethacin. In tail flick test, theincrease in reaction time by chloroform solvent extraction of L welwitschii was established at 200mg/kg. While this study showed that the plant extract may be safe for medicinal purpose, its antiinflammatory and analgesic potencies are not as comparable to that of the standard drug, indomethacin.
Keywords: Lannea welwitschii; leaf extracts; anti-inflammatory; analgesic; haematology