Terpene
Terpenes are a large class of natural organic compounds, over thirty thousand in total, that contribute to the distinctive scents and flavors of various fruits, flowers, and spices. These compounds are primarily derived from plant life, with some contributions from insects and marine organisms. Terpenes are composed of isoprene units, and their classification depends on the number of these units—ranging from hemiterpenes, with one unit, to tetraterpenes, with eight units. Common extraction methods for terpenes include distillation and expression, which allow for the isolation of these compounds from their organic sources.
Widely used in the production of perfumes, flavorings, essential oils, and medicines, terpenes like lavender and tea tree oil are especially notable for their aromatic properties and potential therapeutic effects. In particular, terpenes derived from the marijuana plant have garnered attention for their varied scents and potential medical benefits, especially in managing symptoms related to conditions like anxiety and cancer treatment. Additionally, researchers are exploring the use of terpenoids as biofuels, aiming to develop sustainable alternatives to fossil fuels. Overall, terpenes represent an important and versatile group of compounds with applications across multiple industries.
Terpene
A terpene is one of more than thirty thousand members belonging to a class of natural organic compounds that give fruits, flowers, and spices their signature scents and flavors. Terpenes that have been dried and cured through a process called denaturing are called terpenoids. Both forms are widely used in perfumes, flavorings, essential oils, and medicines. The vast majority of terpenes come from plant life but a few insects, most notably termites and some butterflies, and some marine organisms also produce terpenes.
Types and Characteristics
Terpenes are composed of units of isoprene, which is a hydrocarbon. Each terpene contains several five-carbon isoprene units that attach to one another like links in a chain to form a particular terpene molecule. Each link always consists of five carbons; this is known as the C5 rule or isoprene rule. Different types of terpenes are defined by the number of five-carbon isoprene units they contain:
Hemiterpenes – five carbon atoms, or one isoprene unit
Monoterpenes – ten carbon atoms, or two isoprene units
Sesquiterpenes – fifteen carbon atoms, or three isoprene units
Diterpenes – twenty carbon atoms, or four isoprene units
Triterpenes – thirty carbon atoms, or six isoprene units
Sesquarterpenes – thirty-five carbon atoms, or seven isoprene units
Tetraterpenes – forty carbon atoms, or eight isoprene units
Additional types include polyterpenes and norisoprenoids, both of which contain much longer chains of isoprene units.
Most terpenes will not dissolve in water but can be successfully mixed with chloroform, ethanol, and diethyl ether. They are generally stable, but sesquiterpenes and diterpenes are less stable than most and cannot be stored as easily or for as long as other types.
Terpenes that have been denatured, or oxidized, are technically referred to as terpenoids. Oxidization is the chemical and physical changes a substance undergoes when exposed to oxygen. Since terpenes oxidize easily, the term terpenoids is sometimes applied to substances that are more accurately referred to as terpenes.
Extraction Methods
The two most commonly used techniques to extract the oils containing terpenes are distillation and expression. Distillation uses steam or water and steam to separate the desired components from the rest of the organic material. The organic material is placed on a grid inside a still with a source of steam beneath it. The still is sealed, and steam or a mixture of steam and water is applied to break down the material. Terpenes vaporize and collect in a condenser, which cools the vapor back to liquid form. Most terpenes are not water soluble, so they can be collected easily from the liquid.
In most cases, this level of extraction is sufficient for the resulting product to be used. If greater separation is necessary, fractional distillation can be used to further isolate terpenes or terpenoids. Fractional distillation adds an additional column filled with glass or plastic beads between the still and the condenser. This allows for repeated condensation and greater separation of the distilled components.
Expression, also known as cold pressing, involves crushing or pressing organic material to release oils containing terpenes. In some cases, neither distillation nor expression will effectively separate oils containing terpenes from organic material. When the material is too delicate for expression and too heat sensitive for distillation, solvents may be used to separate the oils from their source.
Common Terpenes and Uses
Many terpenes are integral components of essential oils. Some of the most commonly used terpenes include lavender, peppermint, tea tree, orange, lemon, eucalyptus, rosemary, oregano, chamomile, clove, frankincense, and myrrh. Aromatic terpenes can be mixed into a plain oil, called a carrier oil, which helps diffuse and spread the terpene, or blended with other materials to turn them into cleaners, cosmetics, or other products.
Many terpenes are thought to evoke specific reactions from humans and animals. For example, lavender is believed to be soothing and calming and is often used either alone or as a scent agent in products that help ease anxiety and promote sleep. Other terpenes, such as those in citrus and mint plants, are thought to be stimulating and are used to promote alertness.
Terpenes also are used as natural remedies for several conditions. Tea tree oil, for instance, is used as an antibacterial and antifungal treatment, while menthol, a peppermint terpene that has been oxidized to become a terpenoid, is used as a decongestant.
While many terpenes are well known and used in aromatherapy and other alternative medical treatments, those generated by one particular plant have gained both negative and positive attention. The flower buds of the marijuana plant contain terpenes that can be denatured to terpenoids with various scents. Selectively choosing among these during preparation can alter the scent of the final product. In areas where the sale of recreational marijuana is legal, these designer blends help to expand the market for a variety of "blends" and flavors of the drug.
Medical marijuana growers and users take advantage of the variety of terpenes to choose blends of marijuana aimed at controlling or minimizing specific symptoms, such as chemotherapy-induced nausea and anxiety. Combining certain terpenoids with the phytocannabinoids found in marijuana is thought to assist with pain management and depression in cancer patients and may even affect cancerous tumors directly. Some think these specialized forms of marijuana can help with seizure disorders and other health problems. However, marijuana use in medicine and society continues to be somewhat controversial.
Research
Researchers also have been working on ways to use terpenoids as a fuel source. Scientists have developed methods to genetically alter and combine certain plants, such as switchgrass and eucalyptus, with some forms of bacteria, most notably E. coli and S. cerevisiae, to produce bisabolene, an alternative to the diesel fuels used in jets. Industries that already produce tree pulp and pine chemicals as part of their operation, such as paper plants, are well suited to turn their by-products into fuel, according to researchers. The main hurdle to this process is reducing the price of producing this environmentally friendly biofuel to make it a viable alternative to fossil fuels.
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