D-limonene is the second most widely distributed monoterpene in nature, and its pleasant citrus fruits-like scent makes it one of the most common and widespread terpenes in the fragrance market. It is biosynthesized in secretory cells of cannabis’ glandular trichomes on the surface of the female inflorescence through a reaction leading to cyclization of geranyl pyrophosphate, a precursor common to both cannabinoids and terpenes synthesis.
Cannabis strains that contain Limonene
D-limonene is an aromatic molecule responsible for the lemon-like scent characterizing some chemotypes of cannabis, it is abundant in strains with strong citrus aromas, particularly in “lemon” or “sour” and “Haze” strains, and according to a recent study on a data set of 494 cannabis samples of both “OG” and “kush” strains – plentiful in the ‘OG’ strains.
Limonene and its interaction with human metabolism
This aromatic compound is highly bioavailable and rapidly metabolized by the human body (oral administration of d-limonene is quickly and almost completely absorbed in the gastrointestinal tract, despite there are indications of accumulation and retention in adipose tissues such as the brain).
Furthermore, d-limonene is non-toxic (the estimated lethal dose is of 0.5–5 g·kg-1 in humans).
The medicinal properties of Limonene
From a medical point of view, results from studies on lemon and other citrus essential oils (EOs) in mice and humans, highlighted a powerful anxiolytic effect of D-limonene due to its ability to increase serotonin and dopamine levels by interacting with a subtype of serotonin receptor named “5-HT1A”.
Employed at high doses in breast cancer patients, limonene has also shown anti-tumor activity, by inducing the death of cancer cells. Furthermore, limonene has widely proved to treat gastro-oesophageal reflux, increase blood pressure and to have strong free radical scavenging properties.
D-limonene has also shown effective anti-bacterial and anti-fungal properties and the ability to rapidly penetrate into cell membranes thus promoting the absorption of other terpenes.
Medical properties summary:
- Powerful anxiolytic effect (Calming, anti-anxiety effects)
- Anti-tumor activity at high doses in breast cancer patients
- Proven treatment against Gastro-oesophageal Reflux Disease (GERD) and heartburn
- Increases blood pressure
- Reduces Free Radicals in human cells
- Effective anti-bacterial and anti-fungal properties
All these medical and pharmacological properties of limonene are enhanced by the combined action of this terpene with some cannabinoids, in particular CBD, CBG and THC, which have been demonstrated a powerful entourage effect with this aromatic compound (Table 1.)