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Understanding the Properties of α-humulene to Guide Future Research

Published: 03/05/2024

At Curaleaf Clinic, we’re dedicated to advancing medical knowledge on natural compounds from the cannabis plant. Terpenes and terpenoids are a vast and diverse group of compounds found extensively in the plant world. Our latest research paper dives into the research on α-humulene, a sesquiterpene found in essential oils of various plants such as Humulus lupulus (hops) and Cannabis species. This compound has drawn scientific interest due to its reported effects. Our recent study aimed to separate fact from fiction by performing a scoping literature review.

What is α-humulene?

α-Humulene, also known as α-caryophyllene, is a natural compound found in the essential oils of various plants, including hops and cannabis. It is known for its distinctive aroma which is characteristic of hops.

Its potential properties and abundance in various plant sources make α-humulene a subject of interest for medical applications. However, despite promising preclinical evidence, there remain barriers to its clinical translation.

For example, while some plant species are known to be rich sources of α-humulene, there is a lack of consensus on a named plant species that consistently yields high concentrations of the compound. Furthermore, much of the research to date has utilised a combination of organic compounds contained within the plant essential oil, rather than assessing the properties of α-humulene in isolation. It is therefore important to evaluate studies that specifically report the properties of α-humulene.

A recent scoping review, conducted by researchers from Curaleaf Clinic and Curaleaf International, alongside the Imperial College Medical Cannabis Research Group aimed all research on the biomedical effects of α-humulene in one resource.

Results of the Review

A scoping review was conducted of EMBASE, MEDLINE and PubMed databases up to 14th July 2023. All studies describing original research on α-humulene extraction, and preclinical and clinical research were included for review.

A total of 340 articles were included for qualitative synthesis: 307 studies reported the extraction yields of α-humulene; 32 studies evaluated the preclinical properties of α-humulene (including 20 in vitro, 6 in vivo, and 6 combined in vitro and in vivo studies). However, no studies assessed the clinical properties of α-humulene.

Preclinical Properties of α-humulene

Research highlighted in the scoping review conducted up to July 2023 has demonstrated that α-humulene exhibits anti-inflammatory activity. For instance, studies have shown that α-humulene can reduce inflammation markers in paw oedema in rodents and is effective in reducing airway inflammation in asthma models.

Studies also evaluated the effects of α-humulene on cancer models showing some potential promise. With cancer in particular it is important to be mindful of the potential differences between effects seen in a laboratory on cells and animals and the potential effects that it may have in humans.

These preclinical studies also demonstrated varied antimicrobial potential spanning antibacterial, antiparasitic, and antifungal effects. This includes disrupting biofilm formation, which is associated with antibiotic resistance.

Studies on cells and in animals showed that α-humulene exerts some of its effects through interaction with the CB1 receptor. In one study its effects at the CB1 receptor were shown to be synergistic with the cannabinoid agonist WIN55,212-2

Challenges in Clinical Translation

Despite these promising results, the clinical application of α-humulene faces several challenges. One significant barrier is the variability of α-humulene yields across different plant species, which complicates the standardization of extraction processes for medical use.

Moreover, no studies in humans have examined the effects of isolated α-humulene, with many researchers using a combination of organic compounds from essential oils, thus clouding the specific efficacy of α-humulene.

This means that whilst there is promising preclinical data on the effects of α-humulene it would be premature to conclude that these effects would also be seen in humans. The pathway to clinical translation for many medications is littered with many compounds which have failed to show the same effects they initially showed in laboratory studies. Therefore in-human studies are needed to determine whether α-humulene has any medicinal effects.

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