Study: Researchers Discover Rare Flavoalkaloids in Cannabis Leaves
The findings, published in the Journal of Chromatography A, could open new doors for medicinal research beyond the well-known cannabinoids like THC and CBD. The research team, made up of analytical chemists from the university’s Central Analytical Facility, examined three commercially grown Cannabis strains using an advanced two-dimensional liquid chromatography method coupled with high-resolution mass spectrometry. This approach allowed them to separate and identify compounds that would normally be difficult to detect due to their low concentrations and complex structures.
In total, 79 phenolic compounds were found across the three strains. Of these, 25 had never before been reported in Cannabis, and 16 were tentatively classified as flavoalkaloids—a relatively rare type of plant metabolite that combines a flavonoid backbone with a nitrogen-containing alkaloid group. These compounds were found almost exclusively in the leaves of just one of the strains studied.
Phenolic compounds, especially flavonoids, are valued for their antioxidant, anti-inflammatory, and potential anti-cancer properties. While Cannabis has been known to contain more than 750 metabolites, research has focused primarily on cannabinoids and terpenes. This study underscores that the plant’s lesser-known chemical components could also play an important role in its therapeutic potential.
Dr. Magriet Muller, one of the study’s researchers, said that analyzing plant phenolics is inherently challenging because of their low abundance and structural diversity. She had previously developed analytical methods to study phenolic-rich plants such as rooibos tea and grapes and decided to apply these techniques to Cannabis. Professor André de Villiers, the study leader, credited the precision of two-dimensional chromatography for enabling the separation of flavoalkaloids from more abundant compounds, making their detection possible for the first time.
Flavoalkaloids are uncommon in nature and have been reported to possess various biological activities, but their presence in Cannabis had gone unnoticed until now. The discovery adds to growing evidence that the plant’s medicinal potential extends far beyond cannabinoids, and that plant parts often regarded as waste—like leaves—may be valuable sources of bioactive compounds.
The researchers note that while they were able to tentatively identify these flavoalkaloids, their exact chemical structures remain to be confirmed. Future studies will aim to clarify their composition, determine their prevalence in other Cannabis varieties, and explore possible health benefits. Given the rarity of flavoalkaloids and their potential pharmacological uses, this could represent a new frontier in Cannabis-based medicine.
Researchers conclude the study by stating:
The high variability of Cannabis metabolites, coupled with contemporary interest in the product, has elicited extensive research into the constituents of the plant. However, compared to cannabinoids and terpenes, the phenolic secondary metabolites of Cannabis have received relatively little attention. In this contribution, the potential of on-line HILIC × RP-LC-UV-HR-MS for the detailed analysis of polar phenolic compounds in inflorescence and leaf samples of three commercial Cannabis strains was demonstrated. The optimized analytical method reported here provided excellent separation performance (a practical peak capacity above 3000) and high orthogonality (75 %) for different classes of phenolics, including flavone, flavonol and phenolic acid derivatives as well as a notable new class of Cannabis phenolics, the flavoalkaloids. UV contour plots were found to allow for fast visual comparison of samples, while coupling to HR-MS enabled the tentative identification of 79 compounds. The analytical methodology allows us to report the tentative identification of 25 phenolic compounds in Cannabis for the first time.
The three strains analyzed showed clear differences in their phenolic profiles, with one characterized by higher levels of the C-glycosylated flavones orientin, vitexin, cytisoside and their glycosidic derivatives in both inflorescence and leaf extracts, and the other two containing significantly higher levels of acacetin di-glycoside derivatives.
Of particular interest is the discovery of a large number of flavoalkaloids in the leaves of one of the strains. This is the first report of this compound class in Cannabis, made possible by the improved separation provided by HILIC × RP-LC, since the flavoalkaloids co-elute with other phenolic constituents in RP-LC. While the alkaloid moieties of these compounds could not be assigned based on the available HR-MS data, 16 flavone derivatives belonging to four classes of flavoalkaloids were tentatively identified. In light of their relative rarity and reported biological activity, further research aimed at their structural elucidation and assessing their prevalence Cannabis is certainly warranted.
The complexity of the contour plots, and the large differences in phenolic profiles observed for just three strains in the present work, highlights the importance of studying the phenolic composition of Cannabis using high-resolution analytical methods.