Psychoactive plant

Psychoactive plants have been used ritually (e.g., peyote as an entheogen), medicinally (e.g., opium as an analgesic), and therapeutically (e.g., cannabis as a drug) for thousands of years.

The circumscription of taxa is directed by the principles of classification, and the name assigned is governed by a code of nomenclature.

The compounds found in plants are of many kinds, but most can be grouped into four major biosynthetic classes: alkaloids, phenylpropanoids, polyketides, and terpenoids.

Active constituents of the majority of psychoactive plants fall within the alkaloids (e.g., nicotine, morphine, cocaine, mescaline, caffeine, ephedrine), a class of nitrogen-containing natural products.

Examples of psychoactive compounds of plant origin that do not contain nitrogen are tetrahydrocannabinol (a phytocannabinoid from Cannabis sativa) and salvinorin A (a diterpenoid from Salvia divinorum).

Phytochemicals give plants their color, aroma and taste, and protect them from infectious diseases and predators.

This fact suggests that phytochemicals act as antioxidants to protect the body from oxidative damage caused by water, food, and air.