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Dissecting the Cannabis Plant: Fan Leaves

Over the past decade, juicing fresh fruits and vegetables has moved past trend and become a staple in the diets of the wellness community. It's for good reason: juicing delivers large quantities worth of fresh nutrients in a quick and easy to drink glass – let's be real, no one wants to eat five salads a day. In recent years, juicing fresh Cannabis leaves has gained a reputation as a non-psychoactive preparation delivering potent anti-inflammatory effects, which many attribute to high levels of THCa – the acidic precursor to THC that is known to be anti-inflammatory.

However, according to a study published in 2017 by Dr. Ethan Russo and Dr. Jahan Marcu, fan leaves contain less than 0.05% cannabinoids (1). As home researchers we can visually observe this as truth, since cannabinoids are formed inside trichomes – the glistening figures we otherwise refer to as 'frost'. Volunteer fan leaves (the ones that can be removed with minimal damage to the plant), especially from a vegetative plant, are more than likely frostless, therefore making them cannabinoidless – which leads to the question: if THCa isn't responsible for the anti-inflammatory effects seen from juicing raw, what is?

According to the study, Cannabis leaves are primarily made up of susquiterpenes, flavanoids, and up to 0.02% Canniprene. Quick refresher: a defense mechanism in living plants, terpenes are basically a plant's essential oil, responsible for producing the aromas we associate them with. In speaking about Cannabis, terpenes affect the way cannabinoids (THC/CBD/etc) interact with our body, which is why no two Cannabis plants produce identical effects. Scientists describe this synergistic relationship between cannabinoids and terpenes as the “entourage effect”.


When we discuss terpenes in Cannabis, we often discuss monoterpenes like Mycrene, Pinene, Limonene or Linalool, as they're the ones found in highest concentration in buds, with susquiterpenes clocking in at lower ratios. On the contrary, Cannabis fan leaves contain higher levels of susquiterpenes in comparison to monoterpenes.

B-Caryophyllene is the most commonly found susquiterpene in Cannabis. If you've ever had the pleasure of chomping on a raw top (removing them during the vegetative phase encourages growth) the first thing you'll notice is its peppery taste – that's B-Caryophyllene, the primary terpene also found in Black Pepper, Cloves and Cinnamon. This is where it gets interesting: we've established that trichome-less fan leaves contain minimal cannabinoids, yet Cannabis advisors are consistently reporting cannabinoid-like effects from ingesting them. We're seeing these results because B-Caryophyllene acts like a cannabinoid – studies show that it is a selective, full agonist (stimulator) of CB2 receptors.

Second refresh: CB2 receptors are found in highest concentration in cells originating from the immune system – specifically they're on T and B lymphocytes, monocytes, NK cells, PMN and mast cell lines – as well as in the tissues of the uterus, lungs, and bones, to name a few. Their role in the human body is multifaceted, but studies show their most promising purpose is in regulatory control of inflammation. To further this point, a study found that known anti-inflammatory actions were negated when tested on rodent models whose CB2 receptors were blocked from being stimulated, therefore proving CB2 receptors involvement in inflammation control (1).


Flavanoids in living plants (not just Cannabis) contribute primarily to pigmentation, with the purpose of attracting pollinators. As a secondary function, they work in tandem with terpenes to provide the plant protection. Although originally derived from the latin word flavus, used to describe naturally-occurring shades of yellow, flavanoids known potential extends the rainbow.

As home cultivators and researchers, we can visually observe the concentration of flavanoids in fan leaves thanks to a group of them known as Anthocyanins. Anthocyanins are the flavanoids responsible for the dark hue of beloved purple strains, therefore purple fan leaves indicate a concentration of them.

In general, flavonoids work with cannabinoids and terpenes to contribute to the entourage effect, modulating the how THC interacts in the body and contributing to Cannabis' well know effects (such as being anti-inflammatory and killing cancer). I'm not going to dive into specifics, but for fellow rabbit-holers commonly found flavonoids in Cannabis include “ the O-glycoside versions of the aglycones apigenin, luteolin, kaempferol and quercetin”.

One group of flavonoids identified, aptly named Cannaflavin, is specific to the Cannabis plant. Of the group, Cannaflavin A has been shown to have strong anti-inflammatory properties akin to that of an aspirin – however researchers have struggled to isolate it from Cannaflavin B in leaves. Recently, Cannabis seed sprouts have been noted to be a higher source of Cannaflavin A.

Flavonoids account for approximately 1% of Cannabis leaves plant mass.


Although there is little study into the mechanisms of Canniprene, researchers have determined that this unique-to-Cannabis compound that is present in concentrations up to .2% in Cannabis leaves is not only anti-inflammatory, but it actually prohibits the creation of pro-inflammatory responses.

Deepen the Rabbit Hole

I'm choosing to climb out of the rabbit hole here, and sit with my plants instead. Originally I took my research past this, looking further into cannabinoid accumulation throughout a plant's life cycle – specifically trying to find the cross over point from CBG to THCa. I'm linking the studies I've come across here for those who want to dig in deeper...just be warned, it's a bottomless hole.

The main research paper I referenced is Cannabis Pharmacology: The Usual Suspects and a Few Promising Leads by Ethan B. Russo and Jahan Marcu. Dr. Russo is basically that dude in Cannabis research, and you should pay close attention to the work his company PHYTECS is doing. I highly suggest checking out:

Russo, Ethan & Marcu, Jahan. (2017). Cannabis Pharmacology: The Usual Suspects and a Few Promising Leads. Advances in Pharmacology. (the paper itself, which discusses cannabinoids, terpenes, and flavanoids in depth, as well as pharmacological prospects concerning roots and seeds.)

Presentation on Cannabis Pharmacology

PHYTECs Interactive Tour of the Endoncannabinoid System

As for the rabbit hole I dug but am choosing not to fall into, if you're interested in reading about cannabinoid accumulation in all parts of the Cannabis plant I suggest checking out:

Andre, Christelle M., Jean-Francois Hausman, and Gea Guerriero. “Cannabis Sativa: The Plant of the Thousand and One Molecules.” Frontiers in Plant Science 7 (2016)

Pacifico, D., Miselli, F., Carboni, A., Moschella, A., & Mandolino, G. (2007). Time course of cannabinoid accumulation and chemotype development during the growth of Cannabis sativa L. Euphytica, 160, 231-240.

Isvett Josefina Flores-Sanchez, Robert Verpoorte; PKS Activities and Biosynthesis of Cannabinoids and Flavonoids in Cannabis sativa L. Plants, Plant and Cell Physiology, Volume 49, Issue 12, 1 December 2008, Pages 1767–1782,

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