Evaluation of the Anti-inflammatory Effectiveness of Peppermint (Mentha piperita L.) Leaf Extract on Carrageenan-Induced Paw Edema in Male Wistar Rats (Rattus norvegicus)

Abstract

Peppermint (Mentha piperita L.) contains phytochemical constituents with potential anti-inflammatory activity. This study evaluated the effectiveness of an ethanolic peppermint leaf extract against carrageenan-induced paw edema in male Wistar rats (Rattus norvegicus). Thirty rats were randomly allocated to six groups (n = 5): an uninduced normal group, a saline negative control, diclofenac sodium at 2 mg/kg, and oral peppermint extract at 250, 500, or 1000 mg/kg. The extract was prepared by maceration in 96% ethanol and underwent qualitative phytochemical screening. Paw volume and diameter were recorded across six hourly follow-up observations; surface temperature, rubor, peripheral differential leukocytes, and wet paw mass difference were also assessed. Data were analyzed using ANOVA or Kruskal–Wallis tests with exploratory, unadjusted pairwise comparisons. Extraction yielded 60.83 g (20.28%), and all five screened phytochemical classes tested positive. Overall group differences were significant for all evaluated outcomes (p < 0.001). Among the tested doses, 1000 mg/kg produced the greatest descriptive local response, with inhibition of 18.54 ± 3.61% for volume, 72.02 ± 2.10% for diameter, 85.00 ± 13.69% for rubor, and 53.75 ± 0.24% for baseline-adjusted wet mass. Mean surface temperature was 36.58 °C at this dose. Neutrophil and monocyte percentages increased to 56.80% and 14.40%, respectively, indicating that the leukocyte differential did not normalize with the local response. The findings support local antiedematous activity of the extract, especially at the highest tested dose, while chemical standardization, mechanistic investigation, and safety evaluation remain necessary.