Analgesic activity of aqueous leaf extract of Manihot esculenta Crantz

The aqueous leaf extract of Manihot esculenta Crantz (MELE) has been used in traditional African medicine for the treatment of acute and chronic pain [1] and is claimed to be safe. The analgesic and acute toxicity effects of the extract, given through oral and topical routes, were tested in rodents. MELE (100–400mg/kg, orally) was administered to mice 30min before injection of 10mL/kg, acetic acid (0.6% v/v in normal saline) intraperitoneally [2] or acetylcholine (8.3mg/kg) [3]. In another set, 0.5mL MELE was rubbed onto the depilated abdomen of mice, and at 4h and 8h post-treatment, each mouse was challenged with 0.6%, 10mL/kg, acetic acid or acetylcholine (8.3mg/kg) intraperitoneally. The number of writhes was counted for 15 and 30min., respectively in both experiments. MELE (100–400mg/kg, orally) and (1–4% w/w, topically), like aspirin exhibited significant (P<0.05) inhibition of acetic acid (Orally: MELE: 61.3±3.5%, Aspirin: 70.4±4.8%; Topically: MELE: 47.4±4.5%; Aspirin: 54.9±5.5%) and acetylcholine (Orally: MELE: 54.7±7.5%; Aspirin: 70.1±4.5%; Topically: MELE: 68.0±3.8%; Aspirin: 57.8±4.5%) – induced mouse writhing tests, compared to untreated control. Acute oral administration up to 10g/kg did not cause death within 14 days, but produced mortalities in i.p. administered extract with LD50 of 2.5g/kg. Based on these, the extract may contain orally safe, analgesic principles, justifying its use in traditional African medicine.

References: 1. Anderson, G.J., Coee, F.G. (1996), Econ. Bot. 50, 1:71–107. 2. Koster, R. et al. (1959), Fed. Proc. 18: 418–420. 3. Sancilio L.F. et al. (1977), Agents and Actions 7: 133–144.