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

Pterocephalus hookeri (C.B. Clarke) Höeck, 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. 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. 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. 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. 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.