Inhibitions of mast cell-derived histamine release by different Flos Magnoliae species in rat peritoneal mast cells

Flos Magnoliae (FM) is a commonly used Chinese medicinal herb for symptomatic relief of allergic rhinitis, sinusitis and headache. A number of FM species have been used as substitutes or adulterants for clinical application, although the differences in their pharmacological actions have not been reported. The present study investigated the effects of six identified FM species M. biondii, M. denudata, M. kobus, M. liliflora, M. sargentiana and M. sprengeri, as well as the marker compounds magnolin and fargesin on compound 48/80-induced histamine release in rat peritoneal mast cells (RPMC) in vitro. Ethanolic extracts of all FM species produced a concentration-dependent inhibition of compound 48/80-induced histamine release in RPMC. The rank order of the IC₅₀s was M. biondii<M. kobus<M. liliflora<M. denudata<M. sprengeri<M. sargentiana. The marker compound magnolin, but not fargesin, only slightly inhibited the histamine release. The contents of magnolin and fargesin, determined by using RP-HPLC, varied significantly among these FM species. Magnolin was found in M. biondii, M. kobus and M. liliflora, but not in M. denudate, M. sprengeri and M. sargentiana, while fargesin was only found in M. biondii and M. kobus. These findings provide the first evidence of differences in pharmacological actions of different FM species on mast cell-derived histamine release in vitro. In addition, the marker compounds magnolin and fargesin may not play a major role in the observed pharmacological actions of FM species.