Abstract:
This study was aimed at investigating the anti-inflammatory and analgesic activities of ethanol extract of Hymenodictyon pachyantha stem-bark as well as the possible mechanisms of anti-inflammatory action of the plant extract. The plant material was extracted using 3.5 litres of absolute ethanol. The anti-inflammatory activity of the ethanol extract was evaluated by determining its effect on egg albumin-induced rat paw oedema, phospholipase A2 activity, calcium chloride-induced platelet aggregatory response and membrane stabilization activity. The effect of the extract on acetic acid-induced writhing responses was also investigated. The percentage yield of the ethanol extract was 3.32%. Phytochemical analyses of the extract revealed the presence of flavonoids (1359.268 ± 0.02 mg/100g), terpenoids (2154.695 ± 0.01 mg/100g), steroids (3.782 ± 0.05 mg/100g), saponins (0.405 ± 0.03 mg/100g), alkaloids (268.856 ± 0.12 mg/100g), tannins (1375.930 ± 0.08 mg/100g) and phenols (2900.169 ± 0.15 mg/100g). The acute toxicity test of the extract showed no toxicity up to 5000 mg/kg body weight. The stem-bark extract at 100, 200 and 400 mg/kg body weight significantly (p < 0.05) and dose-dependently inhibited egg albumin-induced rat paw oedema in both early and late stages of inflammation when compared with the untreated control, sustained over a period of 0.5 to 5 hrs. The standard anti-inflammatory drug (indomethacin, 10 mg/kg b. w.) followed a similar trend. The extract also significantly (p < 0.05) inhibited phospholipase A2 activity in a dose-related manner when compared to the control, with a range of 0.1 to 0.5 ml; inhibiting the enzyme activity by 78.92 to 95.59%. The extract also significantly (p < 0.05) and concentration-dependently inhibited platelet aggregatory response when compared to the control. The extract significantly (p < 0.05) inhibited hypotonicity-induced red blood cell membrane lysis in a concentration- dependent manner, similar to the standard drug indomethacin. Ethanol extract of Hymenodictyon pachyantha stem-bark (100, 200 and 400 mg/kg b. w.) significantly (p < 0.05) reduced the number of writhings induced by 0.6% acetic acid solution in a dose dependent manner counted over a period of 20 mins. The results, therefore suggest that the mechanisms of the anti-inflammatory effect may be due to the stabilization of lysosomal membrane, by inhibiting phospholipase A2 and aggregation of platelets. Findings of this investigation provide empirical evidence for the use of Hymenodictyon pachyantha stem-bark extract in folkloric treatment of inflammatory disorders.
