Anti-inflammatory and analgesic activity of aqueous extract of Flos populi

Flos populi is an important traditional Chinese medicine prepared from the male inflorescence of Populus tomentosa Carr. or Populus canadensis Moench (Salicaceae family). Flos populi is mainly used for the treatment of various inflammatory diseases and anti diarrhea in East Asian countries. The objective of this study was to investigate the anti-inflammatory and analgesic properties of the aqueous extract of Flos populi (FPAE).

Cotton pellets-induced granuloma, carrageenan-induced paw oedema, arachidonic acid-induced right ear oedema and xylene-induced ear oedema were used to assess anti-inflammatory activity of FPAE and analgesic activity was evaluated by hot plate test, acetic acid-induced abdominal writhing test and formalin test.

FPAE produced significant dose-response anti-inflammatory activity against cotton pellets-induced granuloma. FPAE at dosages of 50, 100 and 200 mg/kg bw. significantly reduced carrageenan-induced paw edema by 48.84% (P<0.05), 54.95% (P<0.05), and 62.05% (P<0.05) at 5h after carrageenan injection, respectively. FPAE significantly (P<0.05) reduced the ear oedema induced by arachidonic acid and peaked at the dose of 200 mg/kg bw. (40.78%). A significant (P<0.05) dose dependent inhibition of xylene-induced oedema was produced by FPAE and peaked at the highest dose of 200 mg/kg bw. (23.95%). FPAE (50, 100 and 200 mg/kg bw.) produced significant dose-response analgesic activity in the hot-plate test. However, the low percentage inhibition (<50%) suggests that it is not a centrally acting analgesic. Extract at dosages of 50, 100 and 200 mg/kg bw., p.o. significantly reduced acetic acid-induced writhing by 39.6% (P<0.05), 45.4% (P<0.05), and 51.8% (P<0.05), respectively. The extract also caused marked dose-dependent inhibition of formalin-induced pain in the second phase (P<0.05).

The findings in this study suggest that the aqueous extract of Flos populi possesses anti-inflammatory and analgesic activities. These results may support the fact that this plant is used traditionally to cure inflammatory diseases.