Effect of ethanolic extract of Stachys pilifera Benth on subacute experimental models of inflammation and some underlying mechanisms

BACKGROUND AND PURPOSE: This study was designed to evaluate the anti-inflammatory activities of S. pilifera (HESP) in two sub-acute models of inflammation and clarified some possible mechanisms. EXPERIMENTAL APPROACH: Colorimetric methods were used to determine total phenol and flavonoid contents. Carrageenan or formalin-induced rat paw edema (seven days) and multiple application TPA-induced ear edema in mice (9 days) were used. The concentration of IL-1 and TNF-α were measured in the inflamed paw, as well as MDA levels in the serum and liver. Histopathological studies and in vitro anti-inflammatory effects of the extract were also studied using heat-or hypotonicity-induced hemolysis in RBC humans. FINDINGS/RESULTS: Total phenol and flavonoid contents of HESP were 101.35 ± 2.96 mg GAE/g extract and 660.79 ± 10.06 mg RE g extract, respectively. Oral (100 and 200 mg/kg) and topical application (5 mg/ear) of HESP significantly inhibited formalin-induced paw edema and multiple TPA-induced ear edema. The extract also significantly decreased the serum and liver levels of MDA in the carrageenan and formalin tests. The elevated levels of TNF-α and IL-1β in the carrageenan-injected paw were not affected by HESP. The extract (50-800 μg/mL) inhibited heat-or hypotonicity-induced hemolysis. Histopathological examination of the inflamed tissues revealed that HESP inhibited congestion and leukocyte infiltration. CONCLUSION AND IMPLICATIONS: The findings confirmed the potent anti-inflammatory effects of S. pilifera in two sub-acute inflammation models and suggested that these properties were not related to IL-1 and TNF-α, but could be attributed to inhibition of lipid peroxidation, membrane stabilization, and inhibition of leukocyte penetration.