Pyrrolizidine – Structure, Sources & Toxicity
Pyrrolizidine is a nitrogen-containing heterocyclic compound that serves as the backbone for pyrrolizidine alkaloids (PAs). These alkaloids are commonly found in certain plants and are known for their toxic effects on the liver.
Nicotine, a naturally occurring alkaloid in tobacco plants (Nicotiana tabacum), is a derivative of pyridine and pyrrolidine.
Chemical Structure & Properties
- Molecular Formula: C₇H₁₁N
- Structure: A bicyclic system containing a pyrrolidine ring fused to a piperidine ring.
- Derivatives: Pyrrolizidine alkaloids are oxygenated derivatives of pyrrolizidine.
Natural Sources of Pyrrolizidine Alkaloids (PAs)
- Boraginaceae Family (e.g., Comfrey, Heliotropium)
- Asteraceae Family (e.g., Senecio, Eupatorium)
- Fabaceae Family (e.g., Crotalaria)
Toxicity & Health Risks
- Hepatotoxicity (Liver Damage) – PAs are metabolized in the liver into toxic pyrrole derivatives, which cause DNA damage, liver fibrosis, and veno-occlusive disease (VOD).
- Carcinogenic & Mutagenic Effects – Chronic exposure to PAs is linked to liver cancer in humans and animals.
- Food & Herbal Contamination – PAs may contaminate honey, herbal teas, milk, and grains, posing health risks.
- Regulatory Bodies (WHO, FDA, EFSA) set strict limits on PA exposure due to their toxicity.
Industrial & Pharmaceutical Relevance
- Medicinal Plant Research – Some plants with PAs (like Comfrey) were historically used for wound healing and inflammation.
- Pesticide Research – PAs serve as natural insect deterrents.
- Chemical Synthesis – Pyrrolizidine derivatives are used in organic synthesis and alkaloid-based drug development.
Detoxification & Prevention Strategies
- Avoid PA-containing herbal supplements unless certified PA-free.
- Monitor PA contamination in food (especially honey and grains).
- Breeding & Genetic Modification – Efforts to develop PA-free plant varieties.
- Analytical Testing (HPLC, Mass Spectrometry) for PA detection in food and pharmaceuticals.
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