Monocrotaline (Pyrrolizidine Alkaloid · PAH Research Model · Pulmonary Toxin · Informational)

Compound	Monocrotaline
Chemical class	Alkaloid — Pyrrolizidine Alkaloid (Macrocyclic unsaturated PA; pulmonary and hepatic toxin)
CAS	315-22-0
Primary source	Crotalaria spectabilis (showy crotalaria, rattlebox), Crotalaria species
Key applications	Informational reference — pulmonary arterial hypertension research model; hepatotoxic PA; not a supplement ingredient
Claim strength	Not applicable (toxicological and research reference)
Typical form	Research chemical; PAH animal model compound; not a supplement ingredient
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Name origin: From Crotalaria (the plant genus, from Greek krotalon = rattle, referring to the rattling seeds in the pod) + -ine. Monocrotaline is a macrocyclic unsaturated pyrrolizidine alkaloid from Crotalaria spectabilis — a tropical legume widely distributed in Asia, Africa, and the Americas, sometimes grown as a green manure crop or weed. Research model significance: Monocrotaline is one of the most widely used compounds in cardiovascular research — but not for therapeutic purposes. Subcutaneous injection of monocrotaline in rats is the standard experimental model for inducing pulmonary arterial hypertension (PAH), a severe and often fatal condition characterised by progressive occlusion of pulmonary arterioles. The monocrotaline-PAH rat model has been used in hundreds of studies testing new PAH drug candidates. This makes monocrotaline highly significant for pharmaceutical research despite being entirely unsuitable as a supplement or human therapeutic. Toxicology: Monocrotaline causes severe pulmonary vascular injury via pyrrolic metabolite formation (same bioactivation pathway as senecionine) — but with pronounced pulmonary vascular endothelial selectivity causing medial hypertrophy and obliterative changes in pulmonary arterioles. Also causes hepatic veno-occlusive disease similar to other macrocyclic PAs. Supplement status: Monocrotaline is an experimental toxin with no supplement application.

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Monocrotaline — Research and Safety Context

Pulmonary arterial hypertension research model: Monocrotaline injection (60 mg/kg sc in rats) reproducibly induces severe PAH within 3–4 weeks — characterised by right ventricular hypertrophy, pulmonary arteriolar remodelling, and progressive right heart failure. This model has been used to test every approved PAH drug (ambrisentan, bosentan, sildenafil, treprostinil, riociguat) and remains the standard preclinical PAH evaluation tool despite known limitations (acute injury model vs chronic human disease). Research reference.

Crotalaria species as food contamination risk: Crotalaria species are distributed globally as weeds in agricultural fields. PA contamination of grain, pulse crops, and herbal materials from Crotalaria seed admixture has caused PA poisoning outbreaks in India (HVOD from contaminated grain) and South Africa. Agricultural quality control for grain and legume raw materials should include PA testing where Crotalaria weed contamination is possible. Food safety reference.

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Frequently Asked Questions — Monocrotaline

Why is monocrotaline used to study pulmonary hypertension?
Monocrotaline produces a reproducible, dose-dependent PAH phenotype in rats that recapitulates key pathological features of human PAH: pulmonary arteriolar medial hypertrophy, right ventricular pressure overload, and progressive right heart failure. The model is technically simple (single injection) and available to any laboratory — making it the global standard for initial PAH drug efficacy testing. Limitations: the monocrotaline model produces an acute inflammatory/toxic vascular injury rather than the idiopathic vascular remodelling of human PAH, which has driven development of alternative models (SU5416 + hypoxia).

Is Crotalaria a legume crop?
Yes — some Crotalaria species are cultivated as nitrogen-fixing green manure crops (Crotalaria juncea, sunn hemp), cover crops, and forage in tropical and subtropical agriculture. Sunn hemp is widely grown in India, Southeast Asia, and Africa. The monocrotaline-containing species (Crotalaria spectabilis and others) are generally considered agricultural weeds rather than intentional crops. Sunn hemp (Crotalaria juncea) has lower PA content than C. spectabilis but still contains significant PAs — agricultural use products (seeds, leaves) intended for human consumption or herbal use must be PA-tested.

Has monocrotaline toxicity caused human disease?
Yes — monocrotaline-containing Crotalaria weed seed contamination of grain has caused PA-induced HVOD outbreaks in India (particularly Bihar and Rajasthan) where Crotalaria spectabilis seeds contaminate wheat and other grain crops. The clinical presentation is severe hepatic veno-occlusive disease with high mortality. These outbreaks drove the WHO/FAO development of PA risk assessment frameworks and grain quality standards for PA contamination.

Are there any botanical supplements from Crotalaria species?
No supplement applications from Crotalaria species are appropriate due to PA hepatotoxicity. Some traditional uses of Crotalaria (African and Indian traditional medicine) exist but are incompatible with modern supplement safety standards. Sunn hemp (Crotalaria juncea) fibre is used industrially, but the plant parts containing PAs (seeds, leaves) should not be used in food or supplement applications.

Related compounds: Senecionine, Symphytine, Linamarin, Amygdalin

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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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