Alkaloids is a group of mildly alkaline compounds, mostly of plant origin and of moderate molecular complexity. Even in very small amounts, the alkaloids produce strong physiological effects on the body. All contain nitrogen atoms that are structurally related to those of ammonia.
Nearly 3000 alkaloids have been recorded; the first to be prepared synthetically (1886) was one of the simplest, called coniine, or 2-propyl piperidine, C5H10NC3H7. It is highly poisonous; less than 0.2 g (0.007 oz) is fatal. Coniine, obtained from seeds of the hemlock, was the poison used in the execution of Socrates. Some 30 of the known alkaloids are used in medicine. For example, atropine, obtained from belladonna, causes dilation of the pupils; morphine is a painkiller; quinine is a specific remedy for malaria; nicotine is a potent insecticide; and reserpine is a valuable tranquilizer.