Cannabis is famous for THC and CBD, but these are only a small part of the plant’s chemistry.
Scientists have now found a rare group of natural compounds in cannabis leaves, suggesting that parts of the plant often treated as waste may deserve much more attention.
The discovery was made by analytical chemists at Stellenbosch University in South Africa. Their study was published in 2025 in the Journal of Chromatography A and examined the chemical makeup of three commercially grown cannabis varieties from South Africa.
The researchers focused on natural plant chemicals known as phenolic compounds. Plants make these substances for many reasons, including protection from environmental stress, insects and disease.
Some phenolic compounds have attracted medical interest because laboratory research suggests they may have antioxidant or anti-inflammatory effects. However, finding such chemicals in a plant does not automatically mean that eating or using that plant will provide a medical benefit.
In the new study, the researchers identified 79 phenolic compounds in the cannabis samples. Twenty-five had not previously been reported in cannabis, showing that the plant’s chemistry may be considerably more complicated than scientists once thought.
The biggest surprise was a group of 16 compounds that the researchers tentatively identified as flavoalkaloids. These unusual molecules combine chemical features associated with flavonoids and alkaloids and are considered rare in nature.
According to first author Dr. Magriet Muller, flavonoids are widespread throughout the plant world, but flavoalkaloids are much less common. Finding possible examples of them in cannabis for the first time therefore stood out as an unexpected result.
The compounds were not spread evenly across all the cannabis samples. Instead, the suspected flavoalkaloids appeared mainly in the leaves of one of the three varieties, showing that different cannabis plants can have very different chemical profiles.
Detecting these substances was difficult because cannabis contains an extremely complicated mixture of chemicals. More than 750 substances produced through the plant’s normal biological processes have already been reported, making it challenging to separate rare compounds from much more common ones.
To solve this problem, Muller used advanced laboratory methods at Stellenbosch University’s Central Analytical Facility. The approach separates a complex sample in multiple stages and then measures the chemical features of individual substances with great precision.
This allowed the researchers to separate the rare flavoalkaloids from more abundant flavonoids that might otherwise have hidden them. Professor André de Villiers, who supervised the research, said the powerful separation method was an important reason the team was able to make the discovery.
The results also showed surprisingly large differences among the three cannabis varieties. This suggests that studying only a small number of strains may miss many chemicals that occur in other varieties or in different parts of the plant.
Most cannabis research has historically concentrated on cannabinoids such as THC and CBD because of their effects on the brain and their possible medical uses. Leaves and other plant material have received much less attention, particularly when they are left over after more commercially valuable parts are harvested.
The new findings suggest that this material could contain chemicals worth studying for future pharmaceutical or biomedical uses. But researchers will first need to confirm the exact identity of the newly detected compounds and determine what they actually do in cells, animals and eventually humans.
For now, the discovery does not show that cannabis leaves can treat disease. Instead, it reveals an overlooked area of cannabis chemistry and suggests that scientists may have only begun to understand the hundreds of substances hidden inside this unusually complex plant.
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