Imperialine (Steroidal Alkaloid · Bronchodilatory · Antitussive)

Compound	Imperialine (Sipeimine; Fritillaria steroidal alkaloid)
Class	Alkaloid — Steroidal (Ceveratrum-type cevanine skeleton)
CAS	18059-10-4
Molecular formula	C₂₇H₄₁NO₃
Primary sources	Fritillaria imperialis (Crown Imperial), Fritillaria thunbergii (Zhe Bei Mu), Fritillaria cirrhosa (Chuan Bei Mu)
Plant part	Bulbs
Claim strength	Moderate
Key applications	Bronchodilatory; antitussive; anti-inflammatory; smooth muscle relaxation
Buy from Herbuno	Availability on request — request bulk pricing →

Name origin: Imperialine is named after Fritillaria imperialis (the Crown Imperial lily), though it is also characteristic of Zhe Bei Mu (Fritillaria thunbergii) and Chuan Bei Mu (Fritillaria cirrhosa) — two of the most important TCM respiratory herbs. It is a cevanine-type steroidal alkaloid, sharing the cholestane-derived steroidal carbon skeleton with jervine, cyclopamine, and related Veratrum alkaloids, but with a distinctly different ring modification pattern and far lower toxicity. Traditional use: Fritillaria bulbs have over 2,000 years of continuous use in Chinese medicine as Bei Mu — the primary herbal category for resolving phlegm, stopping cough, and clearing lung heat. Zhe Bei Mu (Fritillaria thunbergii) is used for acute productive cough and phlegm-heat conditions; Chuan Bei Mu (Fritillaria cirrhosa) for chronic dry cough and lung yin deficiency. The steroidal alkaloid fraction — imperialine, verticine, and verticinone — is responsible for the primary antitussive and bronchospasmolytic activities documented for Bei Mu preparations. Research trajectory: Imperialine has been isolated and characterised as the primary smooth muscle relaxant alkaloid of Fritillaria species. It acts via muscarinic receptor antagonism and phosphodiesterase inhibition to relax bronchial smooth muscle, with secondary anti-inflammatory activity. Commercial source: Fritillaria extract is available on request from Herbuno; standardised Bei Mu extracts are a specialty TCM botanical ingredient category.

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Evidence for Imperialine Applications

Bronchodilatory and antispasmodic activity: Imperialine relaxes pre-contracted tracheal and bronchial smooth muscle preparations in vitro with EC₅₀ values in the low micromolar range. In vivo, imperialine and Fritillaria extracts standardised to steroidal alkaloids reduce airway resistance and methacholine-induced bronchoconstriction in rodent models. The mechanism involves both muscarinic receptor (M2/M3) antagonism and cAMP-mediated bronchodilation via PDE inhibition. Claim strength: Moderate.

Antitussive activity: Imperialine suppresses mechanically and chemically induced cough in guinea pig models at doses of 5–20 mg/kg. The cough suppression mechanism is central (brainstem cough reflex modulation) and peripheral (bronchial smooth muscle relaxation reducing stimulus-evoked cough). Fritillaria bulb preparations containing imperialine have been used in TCM cough syrups and traditional formulas with clinical precedent spanning centuries. Claim strength: Moderate.

Anti-inflammatory: Imperialine inhibits NF-κB activation and reduces pro-inflammatory cytokine production (IL-6, TNF-α) in LPS-stimulated macrophage models. In acute lung injury rodent models, imperialine treatment reduces neutrophil infiltration and oxidative damage markers. Claim strength: Moderate.

Cardiovascular effects: At higher doses, imperialine produces mild hypotensive and negative chronotropic effects — consistent with its muscarinic receptor modulation. These cardiovascular effects require consideration in formulation dosing for at-risk populations. Claim strength: Moderate.

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Dosage & Formulator Specification

No isolated imperialine human clinical dosing data are established. TCM Bei Mu preparations (Fritillaria thunbergii or F. cirrhosa) are used at 3–9 g dried bulb per day in decoction, or equivalent in concentrated granule form. Steroidal alkaloid content in Fritillaria bulbs is typically 0.1–0.5% dry weight for imperialine across species; Zhe Bei Mu is generally higher in total alkaloids than Chuan Bei Mu.

Chinese Pharmacopoeia standards for Fritillaria thunbergii specify a minimum of 0.080% peiminine (a related steroidal alkaloid) and characteristic alkaloid HPLC profiles including imperialine. Formulators sourcing Bei Mu extracts should request CoA data confirming steroidal alkaloid content and species authentication (misidentification between Fritillaria species is a documented quality issue in the TCM supply chain).

Fritillaria extracts are typically formulated in respiratory products — cough syrups, throat lozenges, inhalation preparations, and oral supplements for bronchial support. Compatibility with piperine (bioavailability enhancer) and other respiratory herbs (platycodin from Platycodon, andrographolide from Andrographis) is established in TCM formula design.

Safety note: Fritillaria steroidal alkaloids at high doses produce cardiovascular depression (bradycardia, hypotension). Commercial preparations within PhP/TCM recommended dose ranges are considered safe; overdosage risk exists with concentrated isolates. No supplement application with isolated imperialine is currently commercially developed.

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Frequently Asked Questions — Imperialine

What is Bei Mu and which Fritillaria species are used medicinally?
Bei Mu ("North Mother bulb") is a TCM category encompassing multiple Fritillaria species used for respiratory conditions. The main commercial types are Chuan Bei Mu (F. cirrhosa, F. unibracteata — Sichuan species, used for chronic dry cough and yin deficiency), Zhe Bei Mu (F. thunbergii — Zhejiang species, used for acute phlegm-heat cough), and Hu Bei Bei Mu (F. thunbergii var.). They differ in alkaloid profiles and traditional indications; imperialine is a consistent marker across all species.

How does imperialine's mechanism compare to conventional bronchodilators?
Beta-2 agonists (salbutamol, salmeterol) relax bronchial smooth muscle via cAMP elevation through adrenergic receptor activation. Anticholinergics (ipratropium, tiotropium) act via muscarinic receptor blockade. Imperialine combines both mechanisms — muscarinic antagonism and PDE inhibition (analogous to theophylline) — in a single molecule, a multi-mechanism profile that may explain the traditional efficacy of Bei Mu preparations for both acute spasm and chronic bronchial inflammation.

Is imperialine related to the teratogenic Veratrum alkaloids (cyclopamine, jervine)?
Imperialine and Fritillaria steroidal alkaloids share the cholestane-derived steroidal skeleton with Veratrum alkaloids (cyclopamine, jervine, veratramine) but have fundamentally different ring modification patterns and pharmacological profiles. Cyclopamine and jervine are Hedgehog signalling pathway inhibitors with high teratogenicity at low doses. Imperialine lacks Hedgehog pathway activity and has a far superior safety profile — Bei Mu has been used safely in TCM pregnancy preparations (with appropriate professional guidance) for centuries. They are chemically related but pharmacologically distinct.

What distinguishes imperialine from verticine and verticinone?
All three are steroidal alkaloids from Fritillaria species. Imperialine is characteristic of F. imperialis and F. thunbergii; verticine and verticinone are more prominent in F. verticillata. Structurally, verticine differs from imperialine primarily in the presence of an additional hydroxyl group; verticinone is the ketone oxidation product of verticine. All three share antitussive and bronchodilatory activities but with slightly different potency profiles across bioassays.

Related compounds: Verticine, Verticinone, Cyclopamine, Conessine

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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