Terpenes are aromatic compounds responsible for the smell and many medicinal properties in numerous plants, and even some insects. Whilst these compounds have only recently come into mainstream consciousness through the avenue of medical cannabis, they have been utilised in traditional eastern and western botanical medicines for centuries.
Ancient cultures, especially the ancient Egyptians, indirectly appreciated the therapeutic benefits of terpenes through the use of oils and resins rubbed on the skin for their cleansing action or added to medicines and foods for their healing and nourishing properties. Terpenes even show up in the nativity story, with the gifts of frankincense and myrrh, the aromas and actions of the terpenes XX and YY were gifted as a potent offering.
The modern discussion surrounding terpenes in the media is largely centralised around the international adult-use market. In this setting, terpenes are highly regarded for their capacity to act synergistically with cannabinoids, provide medicinal actions and influence subject experience. However, for many decades researchers have been quietly investigating these tiny therapeutic compounds for their benefits to human health and in the management of diseases.
So despite the downturn in research surrounding the medical benefits of cannabis in the late 20th century, research into terpenes – key constituents of the cannabis species – have still been studied extensively, in their synthetic form or derived from other plants. The possibilities for enhancing patient outcomes by actively utilising terpenes profiles in medical cannabis formulations is one of the exciting frontiers of this industry. Moving forward terpenes should continue to be experimented with by researchers and considered with more curiosity by prescribing physicians.
Terpenes are organic hydrocarbon compounds with a foundational five-carbon isoprene unit. The units that branch off the basic isoprene structure are what determines the individual characteristics of each terpene. They are volatile in nature when pressed or disturbed – even gently – they produce distinctive aromas that you would know from common plants like citrus, lavender or the sharp woody smell of pine needles.
Plants produce terpenes for a variety of reasons. The aromatic, sometimes spicy or pungent odours produced by plants serve as a survival and preservation mechanisms, deterring animals and insects from eating them. Conversely, plants produce specific terpenes to aid in attracting pollinators and specific insects to aid in their protection from invasive species or fungi.
Terpenes are also involved in aspects of the plant’s energy, hormonal and oxygenation processes, a reflection of how they may also impact humans.
The sweet, uplifting smell of lemons is caused by the terpene limonene. Those same lemony tones that create appealing aromas in cleaning products, also contribute to the mood-enhancing quality of some medicinal cannabis formulations. It is the application and quantity of the terpenes that determines their effect. Whether you find limonene in cannabis species, CBD oils, fresh lemons or as a food additive in soda, there is no recognisable difference to the chemical structure.
The use of botanical extracts in skincare products presents another everyday encounter with terpenes. By adding plant extracts and essential oils to skincare products not only are we enjoying a pleasant smelling product, but the terpenes are also contributing to extended shelf life and nourishing actions.
Through cognitive awareness or somatic experience, everyone that has encountered the aroma of lavender knows it to have a soothing and relaxing effect, this is largely attributed to the linalool content. This action, that has been revered among herbalists for centuries has now been proven to have scientific validity, with linalool interacting with central nervous system components, that is likely to result in anxiety-reducing and sedative effects.
Terpenes can also interact with our endocrine system by influencing, mimicking or reducing a number of different hormones in the body. Understanding exactly how this occurs is still pretty theoretical, what we are confident in is that many terpenes exhibit estrogenic qualities.
By promoting estrogen or having an antiestrogenic effect, terpenes indirectly have an influence over cellular growth, function and signalling, as well as programmed cell death – apoptosis. In these activities, terpenes are being investigated for the management of menopausal symptoms, hormone-related cancers and inflammatory diseases.Given the use of terpenes has largely been isolated to traditional botanical medicines or aromatherapy, knowledge of their therapeutic application hasn’t been strongly disseminated to the public until recently. As knowledge of these compounds has grown, their medicinal benefits have been clouded by recreational applications, with specific terpene profiles prized for their ability to amplify the intoxicating effects of cannabis and in a more positive sense, contribute to therapeutic relief through the entourage effect.
The entourage effect is the phenomena where plant constituents act synergistically to enhance and modulate each other’s physiological effects. This kind of botanical synergism has long been used in herbal medicine practices. In terms of medical cannabis, the widely acclaimed ‘grandfather of medical cannabis’ Rafael Mechoulam and his colleague Shimon Ben-Shabat first coined this term following investigating the endocannabinoid system, observing the entourage effect in mice studies.Terpenes, together with cannabinoids are thought to produce greater or unique effects together than if they are administered in isolation. This has been noted time and time again especially in relation to THC and CBD, which in many conditions exert much more profound effects when administered together, even in seemingly small doses.
We are still a ways from fully understanding the blends and ratios of terpenes, cannabinoids and other phytochemicals have will the greatest benefit in treating specific conditions. The practical experience of physicians applying personalised cannabinoid medicines for their patients is likely to provide the best outcomes in the short term, while we wait for research to catch up – unveiling details on specific combinations for individual diseases.
A plethora of information has been uncovered on the sedative effects of the already mentioned terpene linalool, especially for its actions in reducing insomnia and anxiety. Medical cannabis has long been researched for its potential in attenuating insomnia symptoms and in many instances, it is cannabis medicines with high linalool content that are most commonly sought out after for aiding in sleep.
Under conditions mimicking stroke or cerebral ischemia in mice, the terpene myrcene was shown to reduce structural and oxidative damage, by inducing endogenous antioxidants, acting as a potent antioxidant itself and by reducing cell death in brain tissue. While these are preclinical outcomes, not always directly relatable to human application, it does give us some hints about how terpenes may contribute to the therapeutic action of medical cannabis instances such as concussion.
Bisabolol is another terpene found in cannabis. This is classically associated with the medicinal benefits of chamomile. Independent of its botanical origins, bisabolol has been linked with reductions in the proliferation of cancer cell lines, prevention of neuronal damage and reduction in amyloid aggregation in the brain. Given what we know about the similar actions of cannabinoids, it is unsurprising there are so many terpenes we complimentary or synergistic properties.
Interest in using medical cannabis to alleviate symptoms and moderate disease progression of Alzheimer’s has gained momentum in recent times.
When we take a broad lens we can observe how medical cannabis shows promise for Alzheimer’s diseases in the anti-inflammatory and anti-anxiety actions of the dominant cannabinoids THC and CBD. With reductions in agitation, irritability and caregiver burden observed in human trials.
When we zoom in we find isolated terpenes also exhibit similar actions. Asides from its classic association with sleep, the terpene linalool has also been investigated as an anti-inflammatory agent with potential for modifying disease markers and behaviours in Alzheimer’s models.
𝛽-caryophyllene is arguably the most commonly found terpene in cannabis and has been researched extensively for its therapeutic effects. This terpene found in pepper and cinnamon as well as cannabis species, and has been examined in animals as an antioxidant and anti-inflammatory. These actions can be correlated to Alzheimers pathology and a multitude of other conditions like IBD, chronic pain and arthritis.
Additionally, 𝛽-caryophyllene is thus far the only terpene we know to directly interact with the endocannabinoid system, the potential of which has yet to be tapped into.
Pinene is another terpene regularly encountered in nature, it is thought to have anti-inflammatory and antibacterial effects and therefore is commonly seen is cleaning products.
Outside hygiene, pinene is recognised for its capacity to affect memory and cognition by inhibiting the breakdown of the neurotransmitter acetylcholine which is involved in stress, memory and learning processes. Preclinical research is still limited here, but researchers believe pinene could help reduce impacts on short term memory and some other intoxicating effects elicited by THC. Similarly to 𝛽-caryophyllene there is potential for pinene in neurological presentations.
The possibility for using terpenes as therapeutic agents to relieve symptomology or stimulate the endocannabinoid system, with or without the use of medicinal cannabinoids or synthetic agonists has vast potential.
Discerning how terpenes and cannabinoids act on disease processes, together and individually, will ultimately provide physicians with a better understanding of how to incorporate terpene knowledge into practical prescriptions
Whilst researchers continue to focus their efforts into new ways of combating COVID-19, a number of researchers are looking into whether cannabis or cannabis derived CBD (cannabidiol) or THC (tetrahydrocannabinol) might offer support for those suffering from severe forms of this infection.