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  • Terpene Series: Limonene

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    Dr Ed
    Dr Ed

    What are Terpenes?

     Terpenes are a diverse class of organic hydrocarbon compounds that are often used as a means of defence by plants and insects that produce them due to their strong aroma and anti-bacterial effect. They are a major component of “essential oils”. Although sometimes used interchangeably with the word “terpenes”, terpenoids (or isoprenoids) are modified terpenes as they contain additional functional groups, usually oxygen-containing. For an overview of terpenes, go here.

    Terpenes are made up of linked, repeating isoprene molecules, making them quite volatile compounds and easily combustible. They have a range of attractive tastes and smells including that of fresh berries, citrus, mint, pine to name just a few.

    Terpenes were adapted by the cannabis plant, as with other plants that produce them, as both a deterrent to predators and as an attractor to pollinators. Terpene production can be influenced by not only the strain of hemp, but the climate, weather, age, maturation, soil type and fertilisers that the plant is exposed to during its growth.

    In the context of cannabis, terpenes are molecules secreted alongside cannabinoids like THC and CBD – they are not only aromatic but may also alter or enhance the function of other cannabinoids as well as providing physiological effects of their own when ingested. Unlike CBD and THC which are abundant, terpenes like limonene are secreted in much smaller quantity. This is one of the reasons we isolate terpenes from multiple species of plants and add increased quantities to our broad-spectrum CBD oils.

      

    What is Limonene?

    Limonene is a colourless hydrocarbon classified as a cyclic monoterpene (a terpene consisting of two isoprene units); it is a terpene with a basic and simple structure as picture below.

    Terpene Limonene

    The name ‘limonene’ is rather fitting at the compound is a major component in the oil of citrus fruit peels, particularly orange and, you guessed it, lemon. Limonene is a major component of the aromatic scents and resins characteristic for numerous coniferous and broadleaved trees: red and silver maple, cottonwoods, aspens and spruce to name just a few.

     

    The Science

    Research into limonene and terpenes in general is not as prevalent as cannabinoids such as THC and CBD although greater research effort is now being spent on investigating certain terpenes. However, unlike some terpenes such as linalool and b-caryophyllene (which we will discuss in later posts), the cellular targets of limonene remain unclear – we’re not even sure if it works in the brain or mainly in the periphery. Despite this some interesting preliminary research surrounding the potential therapeutic use of limonene does exist.

    Most research has looked at the potential anti-tumour effects of limonene. Bear in mind that all of these studies are PRE-CLINICAL being either conducted using rodent models, cancer cell lines or other means of pre-clinical assessment.

    In rodent studies, limonene inhibited the growth of both skin and mammary tumours. The mechanism is thought to be down to modulation of inflammation, oxidative stress and specific cell signalling pathways linked to growth. These studies were closely followed by phase 1 clinical trials to access toxicity and a limited phase 2 trial involving breast cancer patients. Limonene was well tolerated by patients and ‘somewhat effective’. The study authors stated that its relative lack of toxicity and potential therapeutic benefit make limonene worthy of continued exploration.

    Other lab studies (cell lines and rodent models) further suggest that limonene may be potentially useful in the treatment of certain cancers as it appears to have an apoptotic effect i.e. it can induce controlled cellular death. These studies looked at both lung and brain cancer cells.

     

    The science is certainly interesting and could lead to more solid conclusions in the future but as of right now – no one should be claiming that terpenes (and cannabinoids for that matter) ‘cure’ cancer in humans. The data is simply not strong enough to support that conclusion.

    As alluded to previously, it remains unclear how limonene achieves its therapeutic effects and through what signalling systems it functions and which tissues it targets. One study showed that inhalation of limonene vapour increases the expression of both serotonin and dopamine (as well their turnover) in the hippocampus and prefrontal cortex; two areas associated with anxiety and depression. Interestingly, one of the ways in which CBD is thought to help anxiety and anxiety-like systems is through modulation of the serotonin system. This paper specifically talked about the ‘anti-stress’ effects of limonene and that rodents placed in 3 typical behavioural stress tests showed the least stress when receiving the limonene vapour.

    Early results do look promising but as always, we require more clinical evidence before firm conclusions can be drawn about the effects of limonene use in human health.

     

    Why we use Limonene

    In the context of cannabis, terpenes are molecules secreted alongside cannabinoids like THC and CBD – they are not only aromatic but may also alter or enhance the function of other cannabinoids as well as providing physiological effects of their own when ingested. Unlike CBD and THC which are abundant, terpenes like limonene are secreted in much smaller quantity. This is one of the reasons we isolate terpenes from multiple species of plants and add increased quantities to our broad-spectrum CBD oils.

    Limonene, in particular, is a useful terpene. Not only are there numerous reported/potential health benefits associated with its use (which research will continue to scrutinise), but limonene imparts a fresh citrus taste to our oils which our customers love.

    As always, if you are considering using CBD, gather as much information as you can before making a decision. Take a look at the peer-reviewed research about cannabinoids and terpenes, effects and side-effects on high-quality academic sites like PubMed. Another good source of information is our official Facebook group where you can ask CBD-specific questions and receive generous coupon codes.

    If you have any technical questions about our products please reach out to us directly on our website chat.

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