ABSTRACT

The study investigated the analgesic and anti-inflammatory effects of the methanol leaf extract of Heterotis rotundifolia (MLEHR) in albino rats. Cold maceration method was used for the extraction and the extract dried in hot air oven (40 0C).  An acute toxicity test of the extract was done using the up-and-down method, with the extract administered at the highest dose of 4000 mg/ kg.The analgesic effect was tested for using the hot plate model, tail flick model and acetic acid induced writhing model.  The rats were grouped into give groups for these tests. Group A received distilled water (10 ml/kg). Group B received Acetic salicylic acid (ASA) (200 mg/kg). Group C received MLEHR (200 mg/kg). Group D received MLEHR (400 mg/kg). Group E received MLEHR (800 mg/ kg).The anti-inflammatory activity of MLEHR was investigated using the carrageenan induced paw oedema and xylene induced ear oedema models.  Thirty rats were grouped into five groups. Group A received distilled water (10 ml/kg). Group B received acetic salicylic acid (ASA) (200 mg/kg). Group C received MLEHR (200 mg/kg). Group D received MLEHR (400 mg/kg). Group E received MLEHR (800 mg/ kg).In the acute toxicity test, the extract produced neither signs of acute toxicity nor death at the doses used after 14 days of observation. The results of the hot plate model and acetic acid induced writhing showed significant increases in the pain reaction time and a reduction in number of abdominal constrictions respectively in the tested groups when compared to the control. The tail flick test only showed significant increase in pain reaction time in group tested with (800 mg/ kg) of the extract when compared to the control. The extract at all the doses tested, as well as the reference drug significantly (p < 0.05) reduced the oedema formation induced by carrageenan in the tested groups when compared to the control, after 4 hours.The different doses: 200, 400 and 800 mg/kg caused 51, 73 and 81% decrease of ear edema induced by xylene. The effect of MLEHR was dose-dependent and compared favorably to that of the reference drug. The preliminary phytochemical analysis showed presence of flavonoids, alkaloids, sapinins, tannins, fats and oils and carbohydrate. These results suggest that Heterotis rotundifolia may have potent analgesic and anti-inflammatory effects which might justify its folkloric use in management of pain and inflammation