The anti-inflammatory effects of Pyrolae herba extract through the inhibition of the expression of inducible nitric oxide synthase (iNOS) and NO production.

The extract of Pyrolae herba (PH), which has been used as an anti-inflammatory folk remedy in Korea and China, was investigated for its anti-inflammatory action using arachidonic acid, 12-O-tetradecanoylphorbol 13-acetate or carrageenan-induced edema assays. The anti-nociceptive activity of PH was also tested in mice using the acetic acid-induced writhing model. PH showed dose-dependent and significant (P<0.05 at 100-400mg/kg) anti-inflammatory and anti-nociceptive activities in the animal assays. The mechanism of the activities of PH was examined by testing the extract to determine if it inhibits the expression of inducible nitric oxide synthase (iNOS) and the production of nitric oxide (NO) from the murine macrophages, RAW 264.7 cells. Similar to the in vivo activities, both the iNOS expression and NO production were significantly suppressed by PH in a dose-dependent manner. PH also inhibited the activating phosphorylation of p38 MAP kinase and NF-kappaB in these cells. These results provide a scientific basis to explain the effects of PH as an anti-inflammatory folk remedy in Asian countries.