High Quality Content by WIKIPEDIA articles! Phytoncides are antimicrobial allelochemic volatile organic compounds derived from plants. The word, which means "exterminated by the plant", was coined in 1937 by Dr. Boris P. Tokin, a Russian biochemist from Leningrad University. He found that some plants give off very active substances which prevent them from rotting or being eaten by some insects and animals. Various spices, onion, garlic, tea tree, oak and pine trees, and many other plants give off phytoncides. Oak contains a substance called greenery alcohol; garlic contains allicin and diallyl disulfide; Sophora flavescens contains sophoraflavanone G; and pine contains alpha-pinene, carene, myrcene and other terpenes. More than 5000 volatile substances defend the surrounding plants from bacteria, fungi and insects. Phytoncides work by preventing the growth of the attacking organism.