Terpenes are the hydrocarbon molecules found in all plants. They have a 5 carbon base, many of which have 10, 15, or more carbons, making them a very diverse and large class of biologically active molecules. The term comes from turpentine, which is the resin found in pine trees and is responsible for the classic pine scent. The terpenes present in the resin cause the strong smell, and also serve other functions such as attracting pollinators or deterring herbivores. Plants with strong scents like citrus, rosemary, eucalyptus, and lavender all have high levels of distinct terpenes which give them their fragrance, flavor, and often medicinal properties. Essential oils are basically the extractions of terpenes from plants to be used in food, for aroma, or as medicine (Breitmaier 2006).
Cannabis has many biologically active phytochemicals including terpenes and cannabinoids. There are over 100 terpenes identified in cannabis alone. The relative abundance of each terpene varies from strain to strain, and even plant to plant. They are created in the trichomes of cannabis, which are most concentrated on the flowers. However, terpenes are produced in smaller quantities throughout the plant (Andre 2016).
Terpenes are the cause of the wide variety of scents produced by cannabis flowers. High levels of the terpene limonene might cause the buds to smell of citrus, while myrcene gives it a more musky or earthy smell. Researchers are working on using the terpene profiles of cannabis plants to distinguish between hemp, indica, and sativa groups. The terpenes present, and their concentrations, act as markers to distinguish the different varieties (Hazekamp 2016).
Many terpenes have medicinal effects with the ability to cross the blood-brain barrier, interacting with nervous system receptors in the brain. α-Pinene is the most common terpene in nature; found in pine trees, rosemary, and cannabis where it often serves as an insect repellant. In humans, it is an anti-inflammatory and has been shown to enhance memory retention; possibly working against the effects of THC on memory (Russo 2011).
D-Limonene is the second most common terpene and can be found in all plants that have a citrus scent. Limonene has been shown to increase serotonin and dopamine in the brain, has been effective for apoptosis of breast cancer cells, and is useful in the treatment of a variety of other conditions. It is also very easy for the body to metabolize and is completely non-toxic (Russo 2011).
β-Myrcene has demonstrated sedative effects and has even been used as a sleep-aid in Germany. Its presence in cannabis is likely to pair with THC in creating the extremely relaxed sedative effects in marijuana (Russo 2011).
D-Linalool is another terpene commonly present in cannabis, and has been studied in detail for its pharmacological effects. Studies have shown sedative effects in mice and anesthetic properties used to treat cuts and burns. It has also shown effectiveness in decreasing risk of seizures (Russo 2011). There are high amounts of linalool in lavender, which has been used for its medicinal properties for thousands of years. Lavender essential oil is also very popular in aromatherapy.
β-Caryophyllene is often the most common terpene found in cannabis extracts that have been treated with heat. It’s also found in black pepper and has anti-inflammatory effects. This terpene lacks psychoactivity and has been shown to be effective in reducing the risk of gastrointestinal problems, like ulcers, and treating allergic reactions on the skin. Plants may use it to attract insect predators as well as ward off insects that could be harmful to the plant (Russo 2011).
With the help of cannabinoids that are also produced in the trichomes of cannabis, terpenes play an ecological role in the survival of the plant. Cannabis does not suffer from many herbivorous insects due to its high concentrations of these molecules in the thick resin it produces. The resin production is higher in times of stress or when the plant is damaged in order to ward off predators and protect itself. Terpenes and cannabinoids work together to defend against bacteria and fungi threatening the plant. They also are useful in protecting the plant from UV radiation, acting as a chemical protectant similar to melanin in humans (Pate 1994).
Terpenes are responsible for the variety of scents and flavors in cannabis, whereas cannabinoids contribute to the main medicinal and/or psychoactive properties. However, since terpenes have proven to be biologically active in animals, both cannabinoids and terpenes contribute simultaneously to the effects cannabis can have on the body. Limonene’s ability to enhance serotonin and dopamine in the brain, work with THC which has similar effects.
Studies have shown that CBD can even be used to treat acne. Terpenes like linalool, limonene, and pinene in essential oils have also been proven to have anti-inflammatory and preventative uses for acne. All of these terpenes and CBD are found in cannabis together, suggesting its ability to treat acne with many chemicals at the same time, that all derived from the same natural source (Russo 2011).
There are potentially many applications of this synergy between the molecules in cannabis, most of which have not yet been thoroughly researched. However, terpenes are without a doubt the reason for the incredible variety of scent and flavor that cannabis has to offer.