Scientists have discovered rare flavoalkaloids and dozens of previously unreported phenolic compounds in Cannabis leaves, suggesting that the plant material often discarded as waste may contain a rich source of potentially useful chemicals. The findings, published in the Journal of Chromatography A, were made by researchers at Stellenbosch University in South Africa, who analyzed commercially grown Cannabis samples. Flavoalkaloids are a rare subgroup of phenolic compounds, which are naturally produced by plants and include substances involved in pigmentation, defense, and protection from environmental stress. The researchers identified 79 phenolic compounds across three strains of Cannabis, with 25 of these compounds previously unreported in the plant. Sixteen of the compounds were tentatively identified as flavoalkaloids, providing the first evidence that this rare class of chemicals occurs in Cannabis leaves. Most of the flavoalkaloids were found primarily in just one of the three strains, highlighting the variability in the chemical composition of Cannabis. Dr. Magriet Muller, an analytical chemist at Stellenbosch University and first author on the paper, noted that studying plant phenolics is challenging due to their low concentrations and complex structures. The chemical complexity of Cannabis, which is known to contain more than 750 metabolites, made the results particularly surprising. The discovery was made using advanced analytical techniques developed by Muller, which combine comprehensive two-dimensional liquid chromatography with high-resolution mass spectrometry. These methods allowed the researchers to examine the phenolic chemistry of Cannabis in greater detail. Prof. André de Villiers, Muller's study leader, emphasized that the separation achieved using the technique was key to spotting the rare compounds. He noted that the excellent performance of two-dimensional liquid chromatography allowed the separation of the flavoalkaloids from the more abundant flavonoids, enabling the detection of these rare compounds for the first time in Cannabis. The findings highlight the importance of developing better separation methods to reveal substances that were present but difficult to distinguish using less powerful techniques. While much of the scientific attention on Cannabis has focused on cannabinoids, the new research suggests that there is much to be learned about the plant's non-cannabinoid chemistry. The leaves, in particular, may deserve closer scrutiny as they could contain phenolic compounds with properties relevant to biomedical research.