Any of a class of nitrogenous organic compounds of plant origin that have pronounced physiological actions on humans. They include many drugs (morphine, quinine) and poisons (atropine, strychnine)
Any of the narcotic, analgesic, and addictive alkaloids derived from opium, such as morphine, codeine, and papaverine.
An alkaloid of plant origin.
Any of a large class of toxic alkaloids with a structure based on pyrrolizidine, which occur widely in plants and can cause liver damage in humans and livestock if ingested.
A liquid amine which is the parent of a series of alkaloids and other compounds occurring in plants, including atropine, hyoscyamine, and cocaine; any of these compounds. Frequently attributive, especially in tropane alkaloid.