Alkaloids are compounds produced by bacteria, fungi, plants and animals. Many are extracted and purified by acid-base extraction. Many are toxic and some have beneficial uses. Examples are cocaine--both an illegal drug and a local anesthetic, caffeine--a stimulant found in plants like coffee and tea and the kola plant and nicotine--found in tobacco. Caffeine is found in seeds, leaves and fruits of some plants, and is a natural pesticide against insects that would eat those plant parts. Caffeine is a central nervous system stimulant and wards off drowsiness. It is shown to restore mental focus and coordination of the body. It is the world's most popular psychoactive substance and is consumed in chocolate, sodas, energy drinks, in headache tablets like Excedrin, coffee, tea, and even in cafeine tablets. These are all reasons that caffeine is extracted from various sources.