Our team of growers want to research and grow cannabis with targeted properties. One of the things we ask is whether a certain characteristic is caused by genetics or the environment. We have researched flavonoids, which are important compounds but less well known than cannabinoids and terpenes. We wondered whether flavonoids, which are the therapeutic pigment compounds in cannabis, can be enhanced or increased. If so, this could become targeted medicines.
Flavonoids are abundant in cannabis and hemp but aren’t well studied or discussed, which is surprising in light of their potential. Cannabis flavonoids provide aroma, flavor, and pigment and are packed with health benefits. Flavonoids can be added to cannabis’ long list of extraordinary therapeutic compounds, and why you may want to ask for available flavonoid testing data whenever you’re selecting your next purchase at a dispensary.
What Are Flavonoids?
Flavonoids are phytonutrients found in all plant species, particularly fruits and vegetables. They account for approximately 10% of the components that are expressed in cannabis. Roughly 20 flavonoids have been discovered in cannabis compared to the 8,000 found in different plant species. These plant pigments and chemicals are not unique to cannabis, as various distinct flavonoids impact different plants in varying degrees. Common flavonoids include cannflavins (cannabis/hemp), carotenoids (carrots), and anthocyanins (blackberries).
Flavonoids in cannabis are non-psychoactive and work synergistically alongside terpenes and cannabinoids to elicit antioxidant, anti-inflammatory, and anti-carcinogenic properties in the human body. The antioxidant characteristics of flavonoids are largely attributable to their innate ability to scavenge free radicals — highly reactive molecules found in nature which can cause changes to our cells and tissues leading to health problems over time. Antioxidants can reduce these harmful effects by inhibiting free radicals.
Flavonoids are phytoprotectants. They act as a defense mechanism for the plant by preventing damage from environmental stressors such as harmful UV rays, pests, fungi, and diseases. The name for flavonoids is derived from Latin flavus, meaning “yellow,” and describes the function in plants as pigments.
There is a strategic reason for producing these colors in flower material — the color lures in pollinators for reproduction. It is most likely that a plant’s genetic background determines the potential for flavonoid expression across the various sub-classes. As such, understanding a plant’s genetics is a crucial first step to developing photogenically-oriented strains that can achieve targeted health benefits.
Flavonoid Subclasses
Chlorophyll, cannflavins, carotenoids, and anthocyanins are subclasses of flavonoids.
Chlorophyll A and B
The primary reasoning behind the lush green hues of cannabis is chlorophyll, a photoreceptor found in the thylakoid membranes in the chloroplasts of plant cells. Chlorophyll is an integral component of plant growth and survival. The word chlorophyll is a combination of the Greek words khlōros, “green” and phullon, “leaf.” There are six types of chlorophyll present within all photosystems of green plants. The two main types are chlorophyll A and chlorophyll B. The main difference is their role in photosynthesis.
Chlorophyll A is the principal pigment involved in the absorption of light and providing energy for oxygenic photosynthesis. It accounts for 75% of total chlorophyll found in all plants and serves as the primary electron donor in the electron transport chain of photosynthesis. Chlorophyll A reflects blue-green colors and absorbs violet-blue along with orange-red colors on the light spectrum at wavelengths that range from ~430 to 660 nanometers, respectively. Chlorophyll B is the accessory pigment, collecting the light energy to pass into chlorophyll A during photosynthesis. It accounts for 25% of total chlorophyll found in all plants. Chlorophyll B reflects a yellow-green color and absorbs violet and orange-red colors on the light spectrum at wavelengths between ~480 to 630 nanometers. However, green light is not absorbed but reflected, making the plant appear green.
Chlorophyll A and B are large, complex molecules that differ slightly in their structure in one area. In chlorophyll A, one carbon atom is attached to a methyl group (-CH3) and in chlorophyll B, one carbon atom is attached to an aldehyde group (-CHO) in the C7 position. This structural difference causes a significant change in the molecule’s absorption spectra. In a chlorophyll compound, small changes can make a big difference. For example, if the magnesium ion in the center of the chlorophyll molecule is replaced with a hydrogen atom, a vegetable’s color when cooked will change from bright green to a dull olive-green color.
Many people incorporate chlorophylls into their diet by consuming nutrient-rich dark green vegetables and herbs such as kale, spinach, and broccoli. An abundance of studies have demonstrated overwhelming health benefits of consuming chlorophyll. For example, chlorophyll has been shown to bind to potential carcinogens and hinder their absorption in the gastrointestinal tract preventing carcinogens from being circulated throughout the body. Chlorophyll also aids in liver detoxification, resulting in possible harmful toxins being naturally expelled from the body. Chlorophyll is chemically similar to hemoglobin, a protein that is essential in red blood cells in transporting oxygen through the body, so it also exhibits blood-building properties. This is effective in treating hemoglobin deficiency disorders including anemia and thalassemia.
Although chlorophyll has a variety of promising health benefits, those in cannabis cultivation are divided about incorporating chlorophyll into their product due to its bitter taste and smell, which is similar to “grass and hay.” Fortunately, during the maturation process, cannabis begins to exhibits many color variations in leaves and buds, which may be attributed to the concurrent depletion of chlorophyll coupled with the increased expression of other subclasses of flavonoids, such as the carotenoids and anthocyanins (Figure 1). Additionally, after the plant curing process, bacteria will consume the chlorophyll, resulting in a more desirable aroma and taste for the consumer. Taken as a whole, cannabis should not only be considered as a plant-based medicine but as a super-food. As such, the notion of juicing immature cannabis plants for ingestion isn’t such a crazy idea.
Cannflavins A and B
Cannabis has its own exclusive flavonoids known as cannflavins A and B. A structure on these flavonoids, known as a prenyl group, helps them attach to cell membranes. Cannflavins A and B can help cells guard against certain toxins as well as provide antioxidant and anti-inflammatory properties. These cannflavins have stronger anti-inflammatory benefits that were up to 30 times more potent by weight than acetylsalicylic acid (aspirin). Their non-psychoactive properties and ability to target inflammation at its source make them ideal painkillers.
Studies have also demonstrated that the underlying basis for the cannflavins’ potent anti-inflammatory properties was their ability to inhibit the in vivo production of two pro-inflammatory mediators, prostaglandin E2 and the leukotriene naturally found in the human body. Unfortunately, cannflavins are not abundant, accounting for less than 0.1% of the fresh weight of the plant. As such, you would have to consume a huge amount of cannabis material to benefit from the pain-relieving activity of the cannflavins (this is not a challenge!). Cannflavins can be extracted and purified and turned into isolates, but the process is not economically feasible at the moment.
Although there is not an abundance of studies on where exactly cannflavins are derived from in the plant, the development of new techniques can aid in the identification of the cannabis genes that are responsible for producing cannflavins and potentially create a natural alternative treatment without the risk of addiction of pharmaceutical pain killers.
Carotenoids
The spectacular fall colors of cannabis crops, like the orange and yellow found in Orange Bud or Lemon Kush, are thanks to the carotenoids, another subclass of flavonoids. Carotenoids produce the yellow, orange, and red hues that are found in many plants as well as in vegetables including carrots and pumpkins. Throughout nature, more than 600 carotenoids have been discovered and some are prevalent in cannabis such as β-carotene (found in carrots), lutein, and zeaxanthin. Studies have shown that some carotenoids can be converted into vitamin A, which aids in supporting vision health, protecting against macular degeneration, and aiding in a healthy immune system. These natural pigments also demonstrate powerful antioxidant properties and are believed to have anti-cancer properties. Carotenoid-rich foods have many health benefits and is another reason why research should be focused on unlocking the full potential of cannabis-based flavonoids.
Anthocyanins
In addition to providing pigment to the plant, anthocyanins are incredibly potent antioxidant molecules. Anthocyanins are responsible for the vibrant red and blue colors found in berries that can also be found primarily in popular cannabis cultivars that everyone knows and loves such as Purple Haze and Blue Dream (Figure 2, CB Dosi), along with the rare red and pink colors found in strains like Pink Panther. The exact origin of anthocyanin-rich cannabis is unknown, however, genetic engineering and/or selective breeding could bring more anthocyanin-rich products to market.
Genetic and Environmental Factors Drive Anthocyanin Content
Anthocyanins have an anthocyanidin core structure bound to various 3- and 5-linked glycosides (sugars). Anthocyanins have been reported to exhibit antioxidant properties. In a recently published study of ours, we evaluated the effect of varying lighting regimens on phytochemical expression in Group III cannabis cultivars (Hildenbrand et al., 2022). We detected numerous anthocyanins glycosides; however, only six prominent compounds, comprised of four different anthocyanidins, were quantifiable.
These included cyanidin-rutinoside, a predominantly reddish-purple pigment, which has been shown to be a potent sirtuin 6 (SIRT6) activator, as well as being involved in telomere maintenance and multiple molecular pathways related to aging.
Peonidin-rutinoside was also detected, which is purplish-red, and has been shown to be an inhibitor of human metastatic breast cancer cells. Two different delphinidin-rutinoside isomers were detected. Delphinidin is a pH-sensitive antioxidant that is blue in acidic pH and red in basic pH. Lastly, two different pelargonidins were detected (diglucoside and rutinoside), which are orange pigments with antioxidant activity.
The highest total anthocyanin concentrations were found in the Gatorade Purple Punch and Blackstar Sherbet cultivars, with cyanidin-rutinoside and peonidin-rutinoside being the most abundant compounds (Figure 3). Conversely, substantially lower concentrations were found in the hemp cultivars CBG127 and White Tahoe Cookies crossed with Purple Punch (Figure 3). Remarkably, CBG127 was devoid of detectable delphinidin-rutinoside 1, delphinidin-rutinoside 2, and pelargonidin-diglucoside under all of the different lighting conditions utilized in the study. However, the dramatic differences in anthocyanin expression amongst the four different Group III cannabis cultivars, particularly between Blackstar Sherbet and CBG127, appears to suggest that anthocyanin expression is primarily driven by genetic factors as opposed to environmental factors.
With that being said, our latest research also suggests that polyhybrid cultivars of Group III cannabis are highly responsive to different lighting regimens and that phytochemical content can be affected by the modulation of light intensity and different red-light frequencies, although additional research is required. These data suggest that Group III cannabis cultivars allocate finite amounts of cellular resources to the production of flower material (yield) and/or the various classes of phytochemicals. This allocation may represent a balance between the major phytochemical classes. For example, we found that Blackstar Sherbet produces relatively higher amounts of anthocyanins but notably lower amounts of cannabinoids, compared to the other three cultivars in our study. This interplay is likely influenced by genetic factors; however, the cellular allocation of resources toward different sub-classes of phytochemical compounds has also now been shown to be altered by lighting intensity and spectrum.
Conclusion
Further research in this field is ongoing and will likely lead to the optimization of breeding strain-specific synergistic ratios of flavonoids along with other compounds for disease-targeted treatments. The hope is that we can control these characteristics while also keeping or enhancing the desirable color variations. Our bodies use plant-derived flavonoids for health, and we believe that we can harness the therapeutic values of the full spectrum of natural phytochemicals found in cannabis.
The key takeaway is that flavonoids work synergistically with cannabinoids, terpenes, and other compounds found in cannabis to produce the wide array of health benefits, aroma, flavor, pigments, and versatile strain characteristics we are only now beginning to understand (Figure 4). In addition to contributing to beautiful vibrant colors found in fruits and vegetables, there is accumulating evidence that various flavonoids found in cannabis exhibit antioxidant, anti-inflammatory, and neuroprotective properties. We are looking forward to learning more about what these compounds can do in the new frontier of medicine.
Hannia Mendoza is a graduate student studying at the University of Texas at El Paso, under the supervision of Zacariah Hildenbrand, a research professor in the Department of Chemistry. Zac is also chief scientific officer and director of Curtis Mathes Corporation. Adam Jacques is a master grower and technical consultant for AgSense in Eugene, Oregon.