A type of alkaloid found in many plants of the Composite and Borage families, once termed a Senecio alkaloid. Some of the pyrrolizidine group have been shown to cause several types of liver degeneration and blood vessel disorders. Several deaths have been attributed to improperly identified plant usage of a Senecio, and some of the desert Boraginaceae annuals and Senecio annuals are overtly toxic. Young leaves and spring roots of Comfrey hybrids should be avoided as well. Not all PAs are toxic, but those that are can produce spontaneous necrosis in the liver hepatocytes of a perfectly healthy person.