Kratom (Mitragyna speciosa) is a plant known for a complex mix of natural chemicals, especially alkaloids. In plant science research, two alkaloids are discussed most often because they help explain many of kratom’s reported effects: mitragynine and 7-hydroxymitragynine, often shortened to 7-OH. These two compounds are related, but they are not the same in how common they are in the leaf or how strongly they act in the body. WHO
Mitragynine is usually described as the main alkaloid in kratom leaf. Scientific reviews commonly report that mitragynine can make up a large share of the total alkaloid content in natural leaf material, sometimes up to about two-thirds. This is one reason mitragynine is often treated as the “primary” compound when researchers measure kratom chemistry and compare products. WHO
7-hydroxymitragynine is typically a minor constituent in natural kratom leaves. A 2025 FDA scientific assessment notes that 7-OH is naturally occurring in kratom, but it is only a small fraction of total alkaloids in natural leaves, described as less than 2% of total alkaloid content. Other scientific work also describes 7-OH as present in very low amounts in raw leaf by mass, which is important because it means the natural leaf usually contains far more mitragynine than 7-OH. FDA , NIH/PMC
Where the difference becomes more serious is potency at opioid receptors. Research summaries and experimental studies report that 7-OH shows much stronger mu-opioid receptor activity than mitragynine, even though it is present in much smaller amounts in natural leaf. This is one reason why scientists and regulators pay close attention to products that are “enhanced” or concentrated for 7-OH, because changing the chemistry can change risk. FDA
Mitragynine and 7-OH are also discussed in research because their signaling is not identical to traditional opioids. Some studies describe these alkaloids as partial agonists at the mu-opioid receptor and report signaling patterns that can be more functionally selective toward G-protein pathways compared to beta-arrestin pathways in lab testing. This does not mean kratom is “safe,” but it is part of why researchers treat kratom alkaloids as a unique area of opioid receptor science. Nature Scientific Reports
Another key point is metabolism. Evidence in the scientific literature indicates that mitragynine can be metabolized into 7-hydroxymitragynine, and reviews discuss CYP3A4 as playing a major role in this conversion based on in vitro human liver systems. This matters because the effects a person feels are not only about what is in the leaf, but also about how their body converts and clears these compounds. NIH/PMC
Drug interaction risk is also part of the chemistry story. Laboratory studies have shown mitragynine can inhibit certain CYP enzymes in vitro, including CYP2D6 and CYP3A4, which are important for metabolizing many medications. This does not prove the exact size of the risk for every person, but it supports why clinicians and researchers warn about mixing kratom with other drugs without medical guidance. NIH/PMC
Putting it all together, mitragynine is usually the dominant alkaloid in natural kratom leaf, while 7-OH is usually present at very low natural levels but can be far more potent at the mu-opioid receptor. Metabolism can also convert mitragynine into 7-OH, and that conversion may differ person to person. From a plant science and consumer safety perspective, the biggest chemistry concern today is not just raw leaf, but products that raise 7-OH levels far above what is typical in nature. FDA
All information presented is for educational purposes only and focuses on plant science research and emerging studies. This content does not replace professional medical advice. Always consult licensed healthcare providers or trained professionals in plant-based science and natural health disciplines. All information provided is thought to be put to date with modern research and you should still do your own research and consult with professionals.
