Senkirkine (Pyrrolizidine Alkaloid · Hepatotoxic · Butterbur Safety Reference)

Compound	Senkirkine (12-Hydroxyjacobin; otonecine-type macrocyclic PA)
Class	Alkaloid — Pyrrolizidine (Macrocyclic ester, otonecine type — N-methyl)
CAS	2318-18-5
Molecular formula	C₁₉H₂₇NO₆
Primary sources	Petasites hybridus (butterbur), Tussilago farfara (coltsfoot), Senecio spp.
Plant part	Leaves, rhizomes
Claim strength	Emerging (toxicology)
Key applications	PA safety reference; butterbur quality control; hepatotoxicity monitoring; informational-only
Buy from Herbuno	Informational reference — see HerbIQ Compound Index →

Name origin: Senkirkine is named after Senecio kirkii (a New Zealand Senecio species), though it is toxicologically most relevant in the commercial context of Petasites hybridus (butterbur) and Tussilago farfara (coltsfoot). It belongs to the otonecine-type macrocyclic PAs — the N-methyl variant of the pyrrolizidine ring, which cannot be converted to N-oxide (unlike retronecine-type PAs) but is still metabolically activated to hepatotoxic pyrroles by CYP3A4. Traditional context: Petasites hybridus (butterbur, Pestwurz) is a well-established European traditional medicine for migraine prophylaxis and allergic rhinitis, with EMA traditional use and some clinical evidence (Petadolex® RCTs). Tussilago farfara (coltsfoot, Huflattich) is used for cough and bronchial conditions in European herbal tradition. Both plants contain senkirkine and other PAs, requiring PA removal for safe commercial use. Research trajectory: Senkirkine's toxicological significance is as a quality control marker for PA removal in commercial butterbur and coltsfoot preparations — not as a therapeutic compound. Safety context: Senkirkine is hepatotoxic via CYP3A4-mediated pyrrole formation, consistent with macrocyclic PAs generally. It is the primary PA monitored in butterbur extract quality specifications.

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Toxicological and Quality Control Profile

Hepatotoxicity mechanism: Senkirkine's otonecine-type structure (N-methyl rather than N-oxide capable necine base) is activated by CYP3A4 to a dehydropyrrolizidine pyrrole alkylating species — the same mechanism as retronecine-type PAs. The N-methyl group of otonecine-type PAs prevents N-oxide formation, so urinary N-oxide excretion monitoring underestimates total PA exposure; analytical detection requires direct parent compound and pyrrole adduct quantification. Claim strength: Moderate (toxicology).

Butterbur PA removal requirement: Commercial Petadolex® (butterbur extract for migraine) is produced using a supercritical CO₂ or solvent extraction process that removes PAs to below the detection limit. This PA-free certification is the critical quality requirement for safe commercial butterbur use. Senkirkine is the primary PA monitored in Petasites extract PA testing because it is the dominant otonecine-type PA in this genus. Claim strength: High (quality/regulatory).

Coltsfoot regulatory action: Tussilago farfara (coltsfoot) preparations for internal use have been restricted or banned in multiple EU member states (Germany, Austria, Switzerland) due to their senkirkine and integerrimine content. The German Commission E issued a negative monograph for internal coltsfoot use, citing PA hepatotoxicity. Coltsfoot is still used in external preparations and some herbal traditions with less-than-full regulatory restriction in other markets. Claim strength: High (regulatory).

Monitoring in botanical supply chain: Senkirkine is a target analyte in botanical PA screening panels. For any Petasites or Tussilago-containing product, senkirkine must be specifically quantified in the EFSA 28-PA panel (where it is included as a priority compound for Asteraceae-family herbs). Claim strength: High (regulatory).

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Regulatory and Formulator Context

Senkirkine is the defining PA quality marker for butterbur (Petasites hybridus) supplement quality. Any commercial butterbur product claiming migraine or allergy indications must demonstrate PA removal to below EFSA-compliant levels — typically certified by LC-MS/MS with senkirkine as a primary target and total PAs below 1 μg/day for adult products.

Formulators sourcing butterbur extract should require: (1) LC-MS/MS PA analysis with the full 28-PA EFSA panel and explicit senkirkine result; (2) extraction method documentation confirming PA-removal process; (3) lot-specific CoA rather than generic specification documents. Petadolex® brand is the reference standard for PA-free butterbur; generic butterbur extracts vary significantly in PA removal quality.

Coltsfoot (Tussilago farfara) containing senkirkine should not be used in internal supplement formulations in EU markets. Topical use in cosmetic preparations is subject to separate assessment; cosmetic regulations in the EU restrict PA-containing botanicals with specific senkirkine limits for leave-on and rinse-off products.

This entry completes the HerbIQ pyrrolizidine alkaloid series (retrorsine, lasiocarpine, lycopsamine, platyphylline from SM24; senkirkine in SM25), providing a comprehensive PA safety reference for botanical supplement formulators.

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Frequently Asked Questions — Senkirkine

What makes senkirkine different from other pyrrolizidine alkaloids like retrorsine?
Senkirkine is an otonecine-type PA — its necine base has an N-methyl group instead of the secondary amine of retronecine-type PAs. This prevents N-oxide formation, which means senkirkine cannot be detected via N-oxide-specific analytical methods and is not excreted as N-oxide in urine. The toxicological significance is similar (CYP3A4-mediated pyrrole formation, hepatotoxicity), but the analytical approach differs — senkirkine requires direct compound quantification rather than N-oxide proxy monitoring.

Is PA-certified butterbur extract completely safe for migraine prophylaxis?
PA-free butterbur extract (Petadolex®) has a relatively good safety record — documented hepatotoxicity cases have been attributed to non-PA-free preparations. Clinical use at 75–150 mg/day (standardised to petasins, PA-free) for migraine prophylaxis has RCT support (Lipton 2004, Neurology: 75 mg twice daily reduced migraine frequency by 48% vs 26% placebo). Long-term safety beyond 4–6 months is less well characterised. PA-free certification is the essential safety prerequisite.

Can coltsfoot (Tussilago farfara) be used safely in herbal formulations?
For internal use in EU markets, the answer is no — German Commission E negative monograph and multiple EU member state restrictions apply. For topical use (external), lower-concentration preparations may be assessed under cosmetic regulations with PA content monitoring. Traditional herbal practitioners outside these regulatory frameworks may use coltsfoot under professional supervision; formulated consumer products targeting EU markets should avoid coltsfoot internal use entirely due to senkirkine content.

How is senkirkine removed from butterbur extract commercially?
Commercial PA removal from Petasites extract uses supercritical CO₂ extraction (which efficiently separates lipophilic petasins from more polar PAs) or liquid-liquid solvent partitioning processes that exploit the polarity difference between petasin diterpenes (non-polar) and PAs (polar, basic). Petadolex® uses a proprietary hydroalcoholic extraction with subsequent alkaloid removal steps. The process is not universal — different manufacturers achieve different PA removal efficiencies, which is why lot-specific CoA documentation is essential for procurement.

Related compounds: Retrorsine, Lasiocarpine, Lycopsamine, Platyphylline

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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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