The name derives from the word alkaline and is used to describe any nitrogen-containing base and organic compounds with one or more of the following features: a heterocyclic compound containing nitrogen, with an alkaline pH and a marked action on animal physiology.
However, there are exceptions to each of these criteria. Alkaloids are produced by a large variety of organisms, including bacteria, fungi, plants, and animals and are part of the group of natural products (also called secondary metabolites).
Many alkaloids can be purified from crude extracts by acid-base extraction.
Many alkaloids are toxic to other organisms.
They often have pharmacological effects and are used as medications, as recreational drugs, or in entheogenic rituals.
Examples are the local anesthetic and stimulant cocaine, the stimulant caffeine, nicotine, the analgesic morphine, or the antimalarial drug quinine.
Most alkaloids have a bitter taste.
