Chemistry and bioactivity of Flos Magnoliae, a Chinese herb for rhinitis and sinusitis

Flos Magnoliae (FM, Chinese name: Xin-yi) is one of the most commonly used Chinese medicinal herbs. It has a long history of clinical use for managing rhinitis, sinusitis and headache. More than 20 different FM species have been used clinically, which makes species identification and evaluation of pharmacological effects of individual chemical ingredients difficult. In this review, we have summarized the current knowledge on FM phytochemistry and its bioactivity activities. The bioactive compounds in FM include both lipid and water-soluble components. More than 90% of the essential components of FM species are terpenoids, including monoterpenes and sesquiterpenes. Lignans and neolignans including tetrahydrofurofuran, tetrahydrofuran and aryltetralin are also present in FM species. A small number of water-soluble compounds have been isolated from Magnolia flower buds, including a benzylisoquinoline alkaloid magnoflorine, an ester ethyl-E-p-hydroxyl-cinnamate and a flavonoid biondnoid. A wide range of pharmacological actions of FM have been reported, including anti-allergy, anti-inflammation and anti-microbial activity. The structure-activity relationship analysis revealed the influence of methylation at position 5 on the 3,7-dioxabicyclo-(3,3,0)-octane backbone of six lignans in antagonistic activities against platelet-activating factor. In addition, the trans stereoisomer fargesin had a much lower bioactivity than the cis stereoisomer demethoxyaschantin. Recent studies have been directed towards the isolation of other bioactive compounds. Further studies on FM may help to develop new anti-inflammatory and anti-allergic drugs.