Limonene (D-Limonene)

Aroma: Citrus

Found in: the rinds and pulps of lemon, oranges, limes, and grapefruits; juniper; cosmetics and cleaning products

Limonene (D-Limonene)-dominant strains: Strawberry Banana, Banana Kush, White Widow, and more. While strains with “Lemon” in their title naturally have some limonene, its content is not necessarily high, in fact, it’s often just the opposite. Don’t expect a limonene-dominant strain to instantly fill the air with citrus aromas, either, as cannabis is always akin to a complex perfume, with a myriad of ingredients making up its aroma.

Boiling Point: 176 ^o C (349 ^o F)

Effects

In the spirit of its invigorating, fresh citrus smell, limonene is most famous for uplifting the mood and alleviating anxiety.

Disclaimer: Bear in mind, however, that the mechanisms of these effects, as well as the ones we’ll get into, remain fairly unknown to scientists. Furthermore, all but one of the studies that have explored this terpene’s potential did so on rodents, and all of them used very large quantities of limonene, especially as they relate to human size and the amounts of limonene that are present in cannabis strains.

Antioxidant

This property should come as no surprise, being that citrus fruits are some of the richest sources of antioxidants. Limonene displayed antioxidant activity on hamster cells in a study from 2015.

Anticancer

In a study from 2018, limonene showed some potential in the treatment of lung cancer, as it “inhibited the growth of lung cancer cells and suppressed the growth of transplanted tumors in nude mice” by stimulating the expression of autophagy-genes, which are the body’s natural defense mechanisms against cancerous cells that lead to their death, or apoptosis.

But again, it’s important to stress on the fact that we’re talking about tiny mice being administered huge amounts of limonene directly, as opposed to large humans taking in trace amounts of limonene that’s present in cannabis.

With that being said, there has been one Phase I human clinical trial on patients with advanced breast cancer, which mainly sought to determine whether limonene was well tolerated at doses that may have some clinical activity. It turned out it was well tolerated and somewhat effective, however, these findings can only serve as a starting point for future research.

Antibacterial

A body of research backs up limonene’s antibacterial properties, which makes perfect sense, being that the terpene is somewhat of a staple of cleaning products. Limonene is effective against Listeria, food-borne bacteria like E.coli, staph, and more.

Anxiolytic

As mentioned above, this is perhaps limonene’s most signature effect, although the exact science behind it remains mostly a mystery. We do know that lemon oil vapor causes an increase in dopamine and serotonin in the brain regions, responsible for anxiety, OCD, and depression. Limonene has also been found to produce “anxiolytic-like effects of (+)-limonene in an elevated maze model of anxiety in mice,” which suggests the terpene can play a viable role in aromatherapy.

Cardiovascular Health

Limonene has also shown some promise in the realm of cardiovascular health, reducing heart rate and blood pressure and mitigating irregular heartbeats in rats.