Kratom’s effects come from naturally occurring chemicals in its leaves called alkaloids. Researchers have identified more than 40 of them, but two dominate the conversation: mitragynine and 7-hydroxymitragynine (7-OH). Understanding the difference between them explains a lot — from why kratom behaves the way it does to why regulators treat 7-OH products differently from leaf.
What are alkaloids?
Alkaloids are nitrogen-containing compounds that many plants produce, often as a defense against insects and animals. Familiar examples include caffeine in coffee, nicotine in tobacco and morphine in the opium poppy. Kratom belongs to the same plant family as coffee, and like many plants in that family, it produces a range of alkaloids with effects on the nervous system.
Mitragynine
Mitragynine is the most abundant alkaloid in kratom leaf and makes up the majority of its total alkaloid content. It is considered the main driver of kratom’s effects.
- Opioid receptors: Mitragynine acts as a partial agonist at mu-opioid receptors, meaning it activates them, but less fully than drugs like morphine.
- Other systems: Researchers believe it may also interact with adrenergic, serotonin and dopamine receptors, which may help explain the stimulant-like effects some people report.
- Metabolism: The liver converts some mitragynine into 7-OH, which researchers think contributes to kratom’s overall effects.
7-hydroxymitragynine (7-OH)
7-OH is present only in trace amounts in dried kratom leaf. It is much more potent than mitragynine at mu-opioid receptors, which is why it gets so much attention.
Because natural leaf contains so little, products built around 7-OH are typically made by converting mitragynine chemically or concentrating extracts. These products can deliver many times more 7-OH than kratom leaf, and they are now the main focus of federal and state regulation. Read more in Kratom vs. 7-OH.
Other kratom alkaloids
Kratom contains many minor alkaloids that are still being studied. Some you may see mentioned:
- Speciogynine, speciociliatine and paynantheine — structurally related to mitragynine and present in smaller amounts. Their individual effects are less well understood.
- Corynantheidine — a minor alkaloid with activity at opioid and adrenergic receptors in lab studies.
- Mitraphylline — an oxindole alkaloid more often discussed in relation to other plants in the same family.
The proportions of these compounds vary with growing conditions, leaf age, harvest timing and processing. That variation is one reason two kratom products can feel different even when labeled the same — see Kratom Strains Explained.
Synthetic derivatives now under federal control
In August 2026, the DEA temporarily placed three manufactured compounds related to 7-OH into Schedule I through August 2028:
- Mitragynine pseudoindoxyl (MP) — a chemical rearrangement product of 7-OH.
- MGM-15 — a synthetic derivative of 7-OH.
- MGM-16 — a fluorinated derivative of 7-OH.
Federal health officials have noted that these compounds do not occur naturally in the plant in meaningful amounts. Their scheduling does not cover botanical kratom leaf.
Why alkaloid content matters to consumers
Because kratom is not regulated as a drug, there is no federal standard for how much mitragynine a product should contain. Content varies between vendors and batches, and products may be “enhanced” with added alkaloids or synthetic compounds without clear labeling. Laws based on the Kratom Consumer Protection Act try to address this by requiring alkaloid labeling and limits on 7-OH. A third-party lab report is the best way to know what a product actually contains — see How to Read a Kratom Label.
Frequently asked questions
What is the main active ingredient in kratom?
Mitragynine. It is the most abundant alkaloid in the leaf and is considered the primary contributor to kratom’s effects.
How much 7-OH is in natural kratom?
Only trace amounts. Federal and state rules generally treat products with 7-OH above a small threshold as concentrated or enhanced, not natural leaf.
Are kratom alkaloids the same as opioids?
They are not chemically the same as drugs like morphine or oxycodone, but mitragynine and 7-OH act on the same opioid receptors, which is why kratom can cause opioid-like effects and dependence.
Sources
- National Institute on Drug Abuse: Kratom
- FDA: 7-Hydroxymitragynine (7-OH): An Assessment of the Scientific Data
- DEA: DEA to Temporarily Schedule 7-OH and Related Substances (July 1, 2026)
- Federal Register: Temporary Placement of Mitragynine Pseudoindoxyl, MGM-15 and MGM-16 (2026-13581)
- HHS: HHS, FDA Commend DEA Action Against Enhanced 7-OH Products
Kratom Universe publishes independent educational information. Nothing on this site is medical or legal advice. Kratom is not approved by the FDA to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before using kratom, and check your state and local laws. If you or someone you know is struggling with substance use, call SAMHSA’s free, confidential National Helpline at 1-800-662-4357.
