Anti-inflammatory and analgesic properties of methanol extract of <i>Annona muricata</i> leaves in animal models

Abstract

Annona muricata has been used by traditional healers to treat varying diseases of inflammatory origin ranging from arthritis, rheumatism, diabetes to cancer with minimal knowledge of scientific verification of these claims. This study seeks to investigate the anti-inflammatory and analgesic effects of the methanol leaf extract of A. muricata in different animal models. Seventy five rats were used for albumen-induced paw ooedema, carragenaan-induced peritonitis and pulmonary ooedema and formalin-induced paw lick test (anti-inflammatory studies), while 25 mice were used for acetic acid induced abdominal writhing test (analgesic study). For each model, twenty five (25) animals were equally divided into 5 groups. Group A (control) was administered with distilled water, while groups B to D were administered extract at doses of 100, 200 and 400 mg/kg respectively and group E received reference drugs (indomethacin or aspirin). Result showed that the extract at doses of 100mg/kg (7.69%) and 200mg/kg (8.60%) significantly (p<0.05) inhibited paw ooedema formation up to 180 minutes post-injection of albumen and was comparable with those of indomethacin (6.00%). Carrageenan-induced peritonitis and pulmonary ooedema was significantly (p<0.05) inhibited by the extract at doses 100mg/kg and 200mg/kg when compared with that of indomethacin (16.1±6.07x103/μl). The analgesic model showed rats administered the extract at 100 and 200mg/kg to significantly inhibit writhe (50.0 and 51.41% respectively) than the aspirin group (30.18%). The study showed that the extract at the dose of 100mg/kg had the most potent anti-inflammatory and analgesic activities.