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Understanding Limonene

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Understanding Limonene

Terpenes are the aromatic molecules that contribute to the fragrance of cannabis. More than 20,000 plant species produce more than 40,000 aromatic terpenes throughout nature. This free training article from Higher Learning LV explores the terpene limonene, one of the most common terpenes in the world and one that is common in marijuana and hep.

A collection of bergamot oranges.
Bergamot oranges make limonene.

A variety of plants produce limonene, including bergamot oranges, all citrus species, juniper, and hemp, produce the aromatic terpene limonene that is technically categorized as a monoterpene. This fragrant molecule features a boiling point of 349° F (176° C), of note to those who vaporize hemp products containing it. Similar to other terpenes, limonene is commonly employed in beauty products, cleaners, food (as a flavor agent), perfume, and medicine.


According to California-based SC Labs, limonene is a major (primary) terpene that "aids in the absorption of other terpenes through the skin and mucous membranes and has been used to treat anxiety and depression." Limonene is also considered a Super Class terpene.


Understanding Limonene: Medicinal Efficacy

Understanding Limonene. Like its sibling terpenes, limonene (also called d-limonene) has been shown to provide a wide range of wellness and health benefits. These include mental health improvements such as reductions in anxiety and general elevations of mood, including the easing of depression.

Molecular structure of limonene.
Limonene molecules.

The molecule's physical benefits include antibacterial and antifungal properties. This special terpene may also help relieve gastrointestinal conditions, including gastric reflux and heartburn. Researchers also believe that it may be an effective treatment for bronchial conditions such as asthma and a variety of allergies.


"Limonene acts as an amplifier or expeditor for other terpenes. It accomplishes this by improving and increasing the absorption of other molecules via topical application to the skin..."

Interestingly, limonene is unique in that it acts as an amplifier or expeditor for other terpenes and chemical compounds. It accomplishes this by improving and increasing the absorption of other molecules via topical application to the skin, sublingual absorption, or ingestion within the digestive tract.


Limonene Research Studies

Understanding Limonene. A variety of peer-reviewed research studies have identified and explored the wellness characteristics of the terpene limonene.


A 2018 study entitled "D-limonene Exhibits Antitumor Activity by Inducing Autophagy and Apoptosis in Lung Cancer" that was published in the journal OncoTargets and Therapy investigated the "antiproliferative and proapoptotic effects on cancer cells" delivered by limonene.

A large bunch of limes.
Limes make lots of limonene.

The study's authors concluded that limonene "may have a therapeutic effect on lung cancer as it can induce apoptosis of lung cancer cells by promoting autophagy." Apoptosis is a genetically pre-programmed process by which cancer cells basically commit suicide after being triggered by outside chemicals such as the terpenes and cannabinoids produced by hemp. This can result in reductions in tumor size.


A 2017 study entitled "D-limonene Exhibits Anti-inflammatory and Antioxidant Properties in Ulcerative Colitis" that was published in the journal Molecular Medicine Reports explored the anti-inflammatory properties of limonene.


The study defined ulcerative colitis (UC) as "a type of inflammatory bowel disease" and hypothesized that the pathogenesis of the disease "involves the activation of the immune system by various microbial antigens based on genetic material and environmental factors."


Reported the study's researchers, "D-limonene has been demonstrated to have important immunomodulatory properties, including antitumor effects, and may alleviate asthma and allergies. In the present study, the anti‑inflammatory effects of D‑limonene were investigated."


The study concluded that limonene delivers "potential antioxidant and anti-inflammatory properties..."

The study concluded that limonene delivers "potential antioxidant and anti-inflammatory properties" and that the compound "may be a novel potential target for the therapeutic effects of UC."


A 2007 study entitled "D-Limonene: Safety and Clinical Applications" that was published in the journal Alternative Medicine Review explored the ability of limonene to treat gallstones, heartburn, and acid reflux.


The study's authors reported that "D-limonene is one of the most common terpenes in nature. It is a major constituent in several citrus oils (orange, lemon, mandarin, lime, and grapefruit)." The study reported that limonene features low toxicity and an acceptable overall safety profile. The research revealed that limonene also acts as "a solvent of cholesterol," giving it clinical applications due to its ability to "dissolve cholesterol-containing gallstones."


"Limonene's 'gastric acid neutralizing effect and its support of normal peristalsis' makes it a valuable therapeutic agent for 'relief of heartburn and gastroesophageal reflux.'"

The research also found that this terpene's "gastric acid neutralizing effect and its support of normal peristalsis" makes it a valuable therapeutic agent for "relief of heartburn and gastroesophageal reflux." In addition, the study reported "the chemopreventive activity" of limonene against "many types of cancer."

A scientists adjusts test tubes in a laboratory.
Studies show potential of limonene.

A 2004 study entitled "Role of D-Limonene in Autophagy Induced by Bergamot Essential Oil in SH-SY5Y Neuroblastoma Cells" that was published in the journal PLOS ONE explored the anti-cancer efficacy of limonene.


This study revealed various cellular chemical mechanisms by which limonene improves the condition of cancer sufferers. The study's authors gained insight into the dosing requirements for improvement efficacy, reporting that their findings "are consistent with results obtained by other research groups showing that relatively high concentrations of limonene are required to affect proliferation of diverse cancer cell lines."

The study found limonene to convey multiple positive health effects beyond its anti-cancer properties, including reductions in systemic inflammation. "These mechanisms might be involved in its biological effects, including ant-inflammatory and chemopreventive activities, reported in preclinical animal models," reported the study, adding that limonene might "play a role in chemoprevention" via its ability to "act as a tumor suppressor in the early phases of tumorigenesis."


The study concluded that limonene produces "pronounced chemotherapeutic activity and minimal toxicity."

The study concluded that limonene produces "pronounced chemotherapeutic activity and minimal toxicity."


A 1998 human clinical trial study entitled "Phase I and Pharmacokinetic Study of Limonene in Patients with Advanced Cancer" that was published in the journal Cancer Chemotherapy and Pharmacology involved 42 patients featuring refractory solid tumors.


The study's authors concluded that "Limonene is well tolerated in cancer patients at doses which may have clinical activity" and that its favorable toxicity profile supports further research, including clinical investigation.

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