Xuan Fu Hua

The most studied single constituent of Flos Inulae. In the water extract of the Inula japonica flower it inhibits JAK/STAT activation in interferon-gamma and TNF-alpha stimulated human keratinocytes, with high computed binding affinity for JAK. Material isolated from the flowers of the co-official species Inula britannica inhibits human neutrophil elastase non-competitively (IC50 3.2 micromolar, Ki 2.4 micromolar), suppresses LPS-induced nitric oxide and prostaglandin E2 with reduced iNOS and COX-2 expression in RAW 264.7 cells, and blocks neutrophil recruitment in zebrafish larvae.

Identified together with 1-O-acetylbritannilactone as an active of the flower water extract, inhibiting JAK/STAT signalling in stimulated human keratinocytes. It is the water-soluble half of the drug's anti-inflammatory profile and would survive decoction, unlike the more lipophilic lactones.

Isolated specifically from the flower heads of Inula japonica and antiproliferative against human breast cancer lines, the most potent reaching IC50 0.20 micromolar in MCF-7 and 6.22 micromolar in MDA-MB-231. This is in vitro cytotoxicity of purified compounds, not a therapeutic property of the decocted drug.

Dimeric lactones characteristic of Inula japonica, cytotoxic to leukaemia lines at IC50 2.2-5.9 micromolar. Note the plant part: the dimers described in the 2015 Fitoterapia work were isolated from the aerial parts of Inula japonica, which in Chinese practice is the separate drug Jin Fei Cao, not from the flower head that constitutes Flos Inulae.

An Inula sesquiterpene lactone with a substantial preclinical antitumour literature, reviewed for its activity in gastrointestinal, breast and lung cancer cell models. All of this work uses the purified compound at micromolar concentrations and none of it bears on the traditional indications of the drug.

Not a chemical constituent but the reason for a preparation rule specific to this drug. The fine hairs of the flower head irritate the pharynx mechanically and provoke coughing or a raw throat if they pass into the strained decoction, so Flos Inulae is decocted wrapped in a cloth bag (bao jian) rather than loose. A patient reporting throat scratchiness or cough after taking a Xuan Fu Hua formula should prompt a check of how the decoction was prepared before the reaction is attributed to the herb pharmacologically.

In traditional East Asian practice the dried flower heads are simmered in water, typically wrapped in a cloth bag because the fine hairs of the flower can irritate the throat. Used to direct qi downward for cough with copious phlegm, belching and nausea. The related fresh plant sap/hairs and sesquiterpene lactones can cause contact dermatitis in sensitive people, as with other Asteraceae.

Xuan Fu Hua is one of the drugs carried in the earliest surviving Chinese materia medica, entered for accumulation of fluid and qi in the chest and flanks and for counterflow qi. The descending action that defines its later use is present from the first record.

Source of Xuan Fu Dai Zhe Tang (Inula and Haematite Decoction), prescribed for persistent belching and epigastric focal distention remaining after sweating, vomiting or purging have been used. This formula remains the principal clinical vehicle for the drug and is the reason it is grouped with the descending and vomiting-arresting herbs rather than with the ascending flowers.

Carries the drug under Xuan Fu Hua and preserves the observation, repeated in later commentary, that where flowers characteristically raise qi this one lowers it. The 2021 Journal of Ethnopharmacology review traces the processing methods and quality criteria that descend from this and the intervening bencao literature.