Terpene University: Part 8 – Limonene

You may remember from part 1, that myrcene is the most common terpene among cannabis strains. Coming in second place is the monoterpene limonene, which can be found in many popular sativa-dominant strains. Limonene is also one of, if not the highest occurring terpene in nature. Terpenes such as limonene, play an important role in the entourage effect by boosting the benefits offered by other cannabinoids and terpenes. If you were at a party, limonene would be the host who makes guests feel comfortable and entertained.

The origin of the word “limonene” may be surrounded by unspoken conflict. However, regardless of whether you’re of the mind that it is derived from the Italian “limone,” or the German “limonen,” it’s clear the terpene was named after the citrus fruit, lemon. In fact, limonene can be found in many citrus fruits as you’ll soon see!

What Is Limonene?

The hydrocarbon and monoterpene known as limonene was discovered in the 1870s by a chemist named Wagner. To be more specific, although the presence of limonene was conceptually recognized in the scientific community, it was Wagner that assembled the first, correct chemical formula for limonene. Then, in 1905, limonene was deliberately and strategically synthesized from pinene by means of pyrolysis (using heat) and from turpentine using chemical catalysts.

It may sound a bit complicated if you’re not a chemist, however, to this day, scientists commonly synthesized high-demand terpenes in a lab. Thankfully for tokers who want some limonene in their life, many cannabis strains biologically synthesize this terpene within its trichomes naturally.

Limonene is one of many natural compounds that cannabis plants synthesize to ward off pests and animals prior to mature seed and fruit development. Not only does the scent of limonene repel many plant-damaging bugs, it also compromises the exoskeletons of many insects, causing damage to their respiratory system. Limonene can also irritate the skin of many animals, including humans. As such, it’s recommended to tread cautiously when using health and skin products containing this natural solvent.

Like other compounds created within the glands of cannabis plants, d-limonene is a highly versatile. It is known as one of nature’s naturally occurring solvents, can be formulated into skincare products to reduce inflammation and acne, and demonstrates therapeutic effects on the body when ingested. Before we investigate d-limonene further, let’s take a quick look at its isomer, l-limonene and how to differentiate between the two.

Limonene Isomers

Many hydrocarbons have the same chemical formula, however, the elements represented in that formula are often arranged or bonded differently, even if slightly. Limonene having the chemical formula C10H16, has two isomers and each isomer has three popular names or synonyms. If you’re looking to source biomass for use in the manufacturing of a broad or full-spectrum cannabis oil that contains limonene, it could prove useful to become familiar with its six common names.

For your convenience, we’re going to break down the common isomers and names of limonene.

If you’ve been keeping up with our Terpene University, you may recall we discussed linalool in part 7. Since limonene has many of the same molecular characteristics as linalool, it might be worth refreshing yourself on the section discussing linalools isomers. That said, let’s jump into the difference between limonene’s chiral variations.

D-Limonene vs. L-Limonene

Both “D” and “L” limonene are considered enantiomeric isomers, in that they mirror each other. The slight shift in molecular layout offers the mirroring molecular architecture different properties and characteristics. When assigning the letter “D” or “L” to a limonene molecule, you are assigning the letter that corresponds to the rotational direction of polarized light when passing through the terpene. We don’t know about you, but we could use a visual about now, so let’s stop for a quick exercise using your free hand.

Plane-Polarized Light Explanation

First, take your hand (it doesn’t matter which) and hold it in front of you as if laying it flat on an imaginary table. Now, imagine your hand is polarized light, or in other words, particles of light traveling along a single, flat plane. Next, imagine there is a huge molecule of your favorite, citrusy terpene hovering directly in front of you. From here, you can discover if the imaginary molecule is d-limonene or l-limonene by moving your hand forward, through the limonene molecule.

If the molecule rotates your hand clockwise, then it was d-limonene. If it rotated your hand counter-clockwise, then it was l-limonene.

And there you have it. You can now identify the limonene isomer by shooting polarized light particles at the terpene and measuring which way the light waves rotate:

• d-Limonene, where the “d” stands for “dextrorotatory” because by definition, it rotates polarized light clockwise.
• l-Limonene, where the “l” stands for “levorotatory” because by definition, it rotates polarized light counterclockwise.

As an added bonus, we’ve identified two more limonene synonyms using the example above — the (+) and (-) limonene isomers. The plus sign is used as a universal, shorter symbol for molecules that are dextrorotatory. And as you’ve guessed, the minus sign is short for the levorotatory characteristic.

No, you’re not high. This stuff is simply trippy (for us anyway.) And if you were enjoying a preroll just now, then we hope you especially enjoyed turning your hand into polarized light.

R-Limonene vs. S-Limonene

Our last set of naming synonyms continue the theme of “clockwise or counterclockwise” much like above. However instead of measuring the direction polarized light rotates, the Cahn Ingold Prelog rule uses a system that assigns a number to each “branch” of the atom by its atomic number, the forth being the lowest. By tracing an imaginary (and very poorly drawn) circle following the substituent numbers in “one, two, three” order.

If the tracing of your imaginary circle follows a clockwise path, then the isomer is designated with an “r,” for “right”. If the tracing follows a counterclockwise path, then the isomer is identified with an “s,” for left. And if you’re wondering how that works, the Latin word for left is “sinister.” The isomer uses the first letter of the Latin word. And if you’re left-handed, you’re still OK in our book.

You Probably Want D-Limonene

Commercially, you will almost always source d-limonene, which also happens to be the isomer found in huge quantities throughout nature and certainly within the world of cannabis cultivation, processing, and manufacturing. L-limonene is often attributed to a more pine and turpentine aroma and is synthesized by plants in significantly lower quantities than its more popular counterpart.

Referencing the image above, cannabis strains containing d-limonene (also (+), (R)) are great sources for flower intended for products formulated to provide customers with a calming, euphoric high.

Where Can You Find Limonene?

By and large, this cyclic monoterpene contributes to both the smell of gasoline in strains such as Lemon Deisel, as well as its citrus flavor. As such, it is frequently found in cannabis trichomes — and in material concentrations. Although citrus fruits and cannabis plants contain the highest quantities of limonene, it can be found in a host of other plants and herbs such as:

• Chamomile
• Mint
• Red Pepper
• Turmeric
• Bay Leaves
• Rosemary

We should at least mention and address the lemony-fresh elephant in the room. As the legend goes (aka, we were unable to secure satisfactory sources), a study in Australia claimed that the two isomers of limonene were responsible for the aromatic differences between lemons and oranges, with the “d” isomer giving oranges their scent, and the “l” isomer smelling of lemon. This is not your run-of-the-mill myth, as it has been re-reported, cited, and quoted widely across reliable and scholarly sources.

In short, new studies claim this is not the case, and claim that d-limonene is also the dominant terpene in lemons. And they claim the other surrounding terpenes and flavonoids result in what we know and love as the lemon scent. We’re not going to lose sleep over it. However, if you’re interested the American Chemistry Association released a paper that can be used to springboard your fact-checking journey.

When you go to enjoy a blood orange, a perfectly ripened grapefruit, or a splash of lemon juice in your water, remember that the same refreshing, uplifting, and even euphoric feelings you experience are shared in many of your favorite cannabis strains — limonene is acting alongside or in solidarity with your body to cultivate these sensations.

What Are the Benefits of Limonene?

Who knew that each time we held an orange or juiced a lemon, we were holding one of the most prominent, organic hydrocarbons in the palm of our hands. And now, this monoterpene is also at our fingertips in the form of a preroll or concentrate cartridge. As you can see, d-limonene has made its way into natural medicine, commercial business ventures, and even the foodservice industry.

Therapeutic Applications

Although limonene has found its way into countless home and industrial applications, the potential for this monoterpene to provide natural, medicinal relief through the use of cannabis flower or concentrate is substantial. It has been used to help alleviate:

• Acid reflux and gastroesophageal reflux disease (GERD)
• Gallstones
• Acne and skin inflammation
• Stress and anxiety

As with all terpenes, limonene is a star player in a strain’s full entourage effect, working with other terpenes and cannabinoids to increase their effectiveness and efficacy. Cannabis is very much in the limonene game, and the benefits to adult use and medicinal customers have only begun to be recognized.

Commercial Applications

Given this terpene exists in high concentrations as the main constituent of an orange’s essential oil, it will come as no surprise that limonene is frequently used as a degreasing solvent and cleaning agent. You may have seen make-it-yourself cleansers that use orange rinds and lemon peels. And you’ve almost certainly seen countless cleaning products leveraging the fruit in their marketing and branding. The reason these products are often effective is because their formulas leverage limonene’s ability to help dissolve grease and residuals composed of fats and oils. Other commercial applications include:

• Automotive – It is used for degreasing engines and cleaning off parts and electronic components.
• Residential – d-Limonene is used as an additive or by itself as a safer alternative to many cleaning products that contain toxic ingredients.
• Fragrance additive – This terpene is frequently added to hygiene and bath products such as soap and shampoo.
• Insect repellant, pesticide – Limonene can kill scale bugs and repel others. Even so, it is not recommended to apply the terpene to plants as it can be damaging to many species, including cannabis sativa L. In fact, limonene has been used to destroy or control cannabis plants.

Foodservice Applications

Next time you’re at a bar or restaurant ordering a few drinks with friends or family, take extra notice if anyone’s beverage is accompanied by a slice of orange or lemon. The reason citrus slices are often added to alcoholic beverages is as scientific as much as it is traditional. As we’ve discussed, the essential oil within citrus peels consists mostly of limonene. This helps to mask the scent of ethanol while adding a citrus aroma to the cocktails.

As a bonus, the citric acid helps buffer the burning sensation often accompanied by a stiff drink or a shot. Whether you’re celebrating with a night on the town or your customers are sitting back to enjoy an evening with an elevated, uplifting strain, limonene will almost certainly be present to keep the levity going. And speaking of sitting back for an elevated, calming, and therapeutic experience, let’s take a look at some cannabis strains that have limonene as a key player in their profile.

Cannabis Strains Containing Limonene

As one of the most commonly occurring terpenes, d-limonene is frequently found in sativa (uplifting) strains. However, it can also be found in the oils of indica strains. Here are some great examples of limonene-rich cannabis strains:

• Lemon Diesel – This strain is often categorized as a hybrid that is indica-dominant. However, terpenes such as limonene and pinene lend themselves to the euphoric, uplifting effects. With genetics from both California Sour and Lost Coast OG, this strain of cannabis is a favorite when treating anxiety or just sitting back to your mind’s meanderings.
• Sour Diesel – The aroma of lemonade and gasoline may not appeal to everyone, but the potent high is sure to light up any customer looking for pain relief or an energetic high to boost mood and creativity. Sour Diesel’s terpene profile may be about as dank as they come, however limonene helps contribute notes of citrus flavor. Limonene pairs nicely with pinene and myrcene to create a widely popular and balanced experience.
• Jack the Ripper (JTR) – Although many will recognize the name of this strain for its terrifying associations, science fiction fans may find Jack the Ripper’s botanical heritage to be just as fear-inducing — Romulan. That’s right, JTR’s great grandfather strain was creatively named, “Romulan.” Crossing the Romulan strain with Cinderella-99 and then again with Jack’s Cleaner, the strain JTR was born. Those looking to employ the services of Jack the Ripper usually do so in the mornings, taking advantage of this strong, sativa’s energetic effects. This can allow patients to enjoy a productive day with reduced pain, inflammation, and anxiety. Limonene teams up with terpinolene to ensure you keep your head up and body off the couch.
• Jack Herer – Ah, good old Jack Herer, we meet again. This highly popular strain can stand toe to toe with even Jack the Ripper when it comes to endowing a patient with uplifting, positive vibes. Although JTR is more likely to warp your mind to unique and sometimes bizarre places, Jack Herer makes for a good toke before a creative session of writing, music, or simply an energized meditation. Limonene doesn’t take front seat among its hydrocarbon comrades, however, it greatly contributes to the entourage effect that popularized Jack Herer’s full-spectrum profile.

If we’ve listed one of your customer’s fan-favorite buds above, then manufacturing cannabis products containing limonene may be a popular piece to your branding puzzle. Products such as gummies or oils that are branded around “sativa”, “euphoric”, or “uplifting” will frequently contain pinene, caryophyllene, and of course, limonene.

A Closing Look at Limonene

Let’s take a last look at the high points of this terpene. Feel free to bookmark this page for a quick, future reference:

Aroma	Citrus (D), dill or turpentine (L) – depending on the isomer and accompanying compounds
Products Containing Limonene	Commonly used as an additive in various foods, juices, candy, cleaning products, perfumes, and cleansers
Natural Occurrences	Lemon and orange peels, grapefruit, and other citrus fruits
Common Benefits	Anti-inflammatory, antioxidant, anxiety relief, improves and elevates mood, stomach protectant
Popular Cannabis Strains	Lemon Diesel, Sour Diesel, Jack the Ripper, Jack Herer

Limonene is one of the most common and abundant terpenes synthesized by cannabis strains. Its highly potent aroma can often overpower other prominent terpenes, making it nearly impossible to identify a strains compound-configuration by scent alone. To fully understand and leverage your (or any) strain’s chemical profile, you need to send a sample to a lab for testing and analysis.

The age-old trope of stoners couch-locked in a hazy room may slowly fade as our knowledge on how terpenes interact and influence our biological and neurological systems evolve. Specific combinations of cannabinoids and terpenes can be grown, synthesized, and customized to allow for the manufacturing of a wider range of products tailored to meet the needs of a wider customer base. To ensure you are offering a variety of products, from wake-and-bake gummies to euphoric, pain-relieving prerolls, be sure to check out flower and cannabis oils containing limonene.

And if you’d like to learn more about other terpenes commonly found in cannabis, check out another article in our Terpene University series below!