Pyrrolizidine alkaloids. There's livertoxic ones, and there's benign ones.
Henriette's herbal blog: The myth that comfrey is completely benign just won't die.
Herbal articles: Pyrrolizidine alkaloids.
Medicinal herbfaq: single herbs.
Henriette's herbal blog: They're cousins of both flavonoids and humanoids.
Henriette's herbal blog: "Coltsfoot" includes both Tussilago and the various species of Petasites.
Henriette's herbal blog: I've avoided plants with livertoxic PAs for years.
Henriette's herbal is one of the oldest and largest herbal medicine sites on the net. It's been online since 1995, and is run by Henriette Kress, a herbalist in Helsinki, Finland.
Plant Healer Magazine: Very relevant to the practitioner.
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