Antinociceptive and anti-inflammatory activities of a standardizedextract of bis-iridoids from Pterocephalus hookeri

Ethnopharmacological relevance: Pterocephalus hookeri (C.B. Clarke) Hiieck, one of the most popular Tibetan herbs, has been widely applied in Tibetan medicine prescriptions. Chemical investigations have led to the isolation of many bis-iridoids. However, the pharmacological activities of bis-iridoid constituents of this plant have never been reported before. Aim of the study: This study evaluated the anti-inflammatory and analgesic activities of afraction of bis-iridoid constituents of P. hookeri (BCPH) in order to provide experimental evidence for its traditional use, such as for cold, flu, and rheumatoid arthritis. Materials and methods: The analgesic effects of BCPH were investigated using the hot-plate test and acetic acid induced writhing test. The anti-inflammatory activities were observed using the following models: carrageenin-induced edema of the hind paw of rats and xylene-induced ear edema in mice. The effects of dexamethasone administration were also studied. Results: BCPH significantly increased the hot-platepain threshold and reduced acetic acid-induced writhing response in mice. Moreover, BCPH remarkably inhibited xylene-induced ear edema and reduced the carrageenin-induced rat paw edema perimeter. Conclusion: The results reveal that BCPH has central, peripheral analgesic activities as well as anti-inflammatory effects, supporting the traditional application of this herb in treating various diseases associated with inflammation and pain.