Terpenes, also known as terpenoids are the largest and most diverse group of naturally occurring compounds. Based on the number of isoprene units they have, they are classified as mono, di, tri, tetra, and sesquiterpenes. They are mostly found in plants and form the major constituent of essential oils from plants. Among the natural products that provide medical benefits for an organism, terpenes play a major and variety of roles. The common plant sources of terpenes are tea thyme, cannabis, Spanish sage, and citrus fruits (e.g., lemon, orange, mandarin). Terpenes have a wide range of medicinal uses among which antiplasmodial activity is notable as its mechanism of action is similar to the popular antimalarial drug in use—chloroquine. Monoterpenes specifically are widely studied for their antiviral property. With growing incidents of cancer and diabetes in modern world, terpenes also have the potential to serve as anticancer and antidiabetic reagents. Along with these properties, terpenes also allow for flexibility in route of administration and suppression of side effects. Certain terpenes were widely used in natural folk medicine. One such terpene is curcumin which holds anti-inflammatory, antioxidant, anticancer, antiseptic, antiplasmodial, astringent, digestive, diuretic, and many other properties. Curcumin has also become a recent trend in healthy foods and open doors for several medical researches. This chapter summarizes the various terpenes, their sources, medicinal properties, mechanism of action, and the recent studies that are underway for designing terpenes as a lead molecule in the modern medicine.
Terpenes: properties and therapeutic benefits
Cannabis contains a large number of terpenes that are therapeutically beneficial to the human body. They are also responsible for the odours that we associate with cannabis, as well as other products that we encounter in day to day life, such as cheese and blueberries.The smell and the taste of cannabis and many other products depend on the presence and proportion of the different terpenes found in aromatic plants. In addition, they have therapeutic effects that enhance and complement the effects of the cannabinoids.
In general, terpenes play an important role in the treatment of pain, inflammation, depression, anxiety, addiction, epilepsy, cancer and bacterial and fungal infections.
Types of terpenes
Although medical cannabis is composed of lots of different types of terpenes, these are the main ones:
- Myrcene (ß-Myrcene): This is the most prominent terpene in the cannabis plant, it can be found in hops, aged mangoes, bay leaves and lemon grass. ß-Myrcene is well known for its medicinal properties in the treatment of general pain and inflammation. Mixed with THC, it has relaxing, analgesic effects at a mental and physical level, it can be used against both psychological and muscular fatigue.
- Limonene: The second most prominent terpene in cannabis is limonene. It can also be found in citrus peels and numerous flowers. With its lemon scent, limonene is an antidepressant, anxiolytic, immunostimulant, antitumor and an antibacterial. Limonene act together with the phytoannanabinoids: THC-A, CBD-A, CBC-A, CBC, CBG as well as others. They are useful when combined with cannabinoids; improving, modulating and enhancing their effects. The cannabis plant has a series of compounds which may be very useful for terpene-based monotherapies and cannabinoid therapies. As limonenes help to dissolve oils and other lipids, they are used to aid weight loss, gastric reflux and heartburn.
- Pinene: This terpene is responsible for the smell of the plants, such as pine and spruce. It is known to be an expectorant, bronchodilator, anti-inflammatory and antiseptic. For thousands of years rosemary and sage (both contain high concentrations of pinene) have been used in traditional medicine to improve memory. This feature can counteract some of the effects of THC. A study done in China in 2015, highlighted the antitumor effects of pinene, when tested on humans.
The combination of terpenes and cannabinoids: the entourage effect
This diversity of components in nature also show the limits of the synthesis of the pharmaceutical industry. When combined with cannabinoids and other plants, terpenes act differently, just as synthesized pure THC has much weaker effect without terpenes. While recognizing the high presence of terpenes in the intensity of plant’s odour, its concentration depends on the variety of medical cannabis and their modes of cultivation. That is why it is very important to know which varieties of medical cannabis have been adapted to suit your needs. On the other hand, it is imperative to consider different forms of consumption of therapeutic cannabis since certain ways can affect the potency of the terpenes.
While there are many terpenes in the natural world, scientists have only studied a handful.
Examples of better-known terpenes include:
Limonene is a common terpene that most people can recognize by its scent. As the name suggests, limonene gives the rinds of fruits such as lemons and oranges their citrusy smell.
A study in Chemico-Biological Interactions notes that limonene contains the following therapeutic properties:
Limonene appears to modulate the way certain immune cells behave, which may protect the body from a range of disorders. Limonene is also safe for people to take as a supplement.
Pinene is another naturally abundant terpene. There are two forms of pinene: a-pinene and b-pinene. Pinene provides the fresh, bright scent of many plants, including pine needles, rosemary, and basil. Pinene may also have some therapeutic benefits.
Shirin-yoku, which means “forest bathing,” is a Japanese therapy that involves taking leisurely walks in the forest, soaking up the atmosphere, and enjoying the scent. Shirin-yoku may have preventive and restorative effectsTrusted Source on a person’s psyche and physiology.
A study in Acta Salus Vitae notes that the amount of pinene in the air of a healthy forest is enough to be therapeutic. Pinene acts as a bronchodilator, allowing more air into the lungs. It also has an anti-inflammatory effect and may fight against some infectious germs when inhaled.
Linalool is most abundant in the lavender plant and gives the flower its rich scent. Linalool is one of the more important compounds in aromatherapy and is responsible for the calming effect many people get when smelling lavender or its essential oil.
A study in Colloids and Surfaces B: Biointerfaces notes that linalool may affect the body in a variety of ways due to a range of properties, including:
Linalool does appear to act on the body, but researchers must study its effects further to understand how people can use it to benefit their health.
Myrcene is a terpene commonly found in plants such as hops, lemongrass, and thyme. The flowers of the cannabis plant also contain myrcene.
Myrcene is a powerful antioxidant. One study Trusted Sourcein mice concludes that myrcene could help protect the brain from oxidative damage following a stroke.
Another study in mice found that myrcene had a similar protective effect in heart tissue. The researchers note that myrcene may be a useful alternative treatment after ischemic stroke.
However, it is important to bear in mind that these studies used very high concentrations of myrcene, up to 200 milligrams (mg) per kilogram (kg) (mg/kg) of weight.
Another studyTrusted Source in a cell model of osteoarthritis noted that myrcene appears to have an anti-inflammatory effect and may prevent the breakdown of some cartilage cells. This could make it useful against osteoarthritis.
Beta-caryophyllene exists in many herbs and vegetables, such as cloves and black pepper.
Similarly to other terpenes, beta-caryophyllene may have an anti-inflammatory effect on the body that could reduce pain levels in some people.
In one animal studyTrusted Source, beta-caryophyllene reduced pain from inflammation and nerve pain. The researches noted that this anti-inflammatory and analgesic effect might be useful for treating long-term chronic pain because the body showed no sign of developing a tolerance to these effects.