Phytocannabinoids are a class of compounds found in plants (phyto-) that act upon the endocannabinoid system. The vast majority of phytocannabinoids are found in the species cannabis Sativa, but other cannabinoids have been found elsewhere in the plant kingdom, such as piper nigrum (black pepper) and echinacea purpurea (purple coneflower). Cannabis plants produce cannabinoids in their acidic forms. These compounds are believed to convey antioxidant, anti-pest, and antimicrobial properties to the plant.
When heated, acidic cannabinoids lose their acid group, a process called decarboxylation, which transforms them into neutral cannabinoids. For example, Tetrahydrocannabinolic acid, THCA, is converted to Tetrahydrocannabinol, THC, when heated. A small amount of conversion from the acidic to neutral form will also occur over time at room temperature. Preparations of cannabis intended to contain the acidic cannabinoids will almost always contain at least a low level of naturally occurring neutral cannabinoids.
While acidic cannabinoids possess medicinal properties, almost all of the research on phytocannabinoids has investigated the neutral forms. These neutral cannabinoids possess a wide array of physiologic effects, and none have been found to be toxic or capable of causing serious injury or death from overdose. In addition to the physiologic effects summarized briefly in this chapter, several cannabinoids have been shown to possess antimicrobial and antioxidant properties, as they do on the plant.