Analgesic and Anti-Inflammatory Effects of 80% Methanol Extract of Leonotis ocymifolia (Burm.f.) Iwarsson Leaves in Rodent Models

Abstract

Background: Pain and inflammation are the major health problems commonly treated with traditional remedies mainly using medicinal plants. Leonotis ocymifolia is one of such medicinal plants used in folkloric medicine of Ethiopia. However, the plant has not been scientifically evaluated. The aim of this study was to evaluate analgesic and anti-inflammatory effects of the 80% methanol leaves extract of Leonotis ocymifolia using rodent models.

Method: The central and peripheral analgesic effect of the extract at 100, 200, and 400 mg/kg dose levels was evaluated using hot plate and acetic acid induced writhing rodent models, whereas carrageenan induced paw edema and cotton pellet granuloma methods were used to screen anti-inflammatory effect of the extract at the same dose levels. Acute toxicity test was also done. Data were analyzed using one-way ANOVA followed by Tukey's post hoc test and p < 0.05 was considered significant.

Results: The extract did not produce mortality up to 2000 mg/kg. All tested doses of the extract showed significant analgesic effect with maximum latency response of 62.8% and inhibition of acetic acid induced writhing. Maximum anti-inflammatory effect was recorded at 6 h after induction, with 75.88% reduction in carrageenan induced paw edema. Moreover, all tested doses of extract significantly inhibited the formation of inflammatory exudates and granuloma formation (p < 0.001).

Conclusion: The study indicated that the extract was safe in mice and it has both analgesic and anti-inflammatory effect in rodent models.

Figure 1

Percentage inhibition of 80% methanol leaf extract of Leonotis ocymifolia on acetic acid induced writhing model in mice. TW (10 ml/kg); ASA, aspirin (150 mg/kg); LO100, extract (100 mg/kg); LO200, extract (200 mg/kg); LO400, extract (400 mg/kg).

Figure 2

Percentage increase in latency time of 80% methanol extracts of Leonotis ocymifolia relative to negative control (TW) based on hot plate method latency time in mice. TW, Tween-80 (2%); MO, morphine (20 mg/kg); LO100, extract (100 mg/kg); LO200, extract (200 mg/kg); LO400, extract (400 mg/kg).

Figure 3

Percentage inhibition of 80% methanol extract of Leonotis ocymifolia on carrageenan induced paw edema model in mice. ASA, aspirin 100 mg/kg; LO100, extract (100 mg/kg); LO200, extract (200 mg/kg); LO400, extract (400 mg/kg).

Figure 4

Percentage inhibition of 80% methanol extract of Leonotis ocymifolia on cotton pellet induced granuloma model in rats. Data is expressed as mean ± SEM, n = 6; TW, 2% Tween-80 (10 ml/kg); dexamethasone (0.5 mg/kg); LO100, extract (100 mg/kg); LO200, extract (200 mg/kg); LO400, extract (400 mg/kg).