Last reviewed September 15, 2026. Educational content for adults 21+. This article is not medical advice and does not recommend a dose or use. Kiody does not sell concentrated 7-hydroxymitragynine (7-OH) products.
The short answer: mitragynine is a monoterpene indole alkaloid and is usually the predominant alkaloid measured in Mitragyna speciosa leaf. It is one constituent of a variable plant mixture, not a synonym for kratom. Cell studies show that purified mitragynine can partially activate the human mu-opioid receptor and interact with other receptor systems. The body also converts a portion of mitragynine into metabolites, including 7-OH. Early human studies describe how mitragynine from characterized leaf preparations enters and leaves the bloodstream, but they do not establish medical effectiveness, a universal safety threshold or a human lethal dose.
The most important rule for reading this research is to identify the material. A result from purified mitragynine does not automatically describe dried leaf, tea, a broad-spectrum extract, an enhanced product or a manufactured 7-OH product. For the wider compound map, start with Kiody’s guide to kratom leaf alkaloids.
Mitragynine is one alkaloid inside a complex leaf
The accepted botanical name for kratom is Mitragyna speciosa (Korth.) Havil., according to Kew’s Plants of the World Online. Its leaves contain dozens of indole and oxindole alkaloids. Mitragynine often produces the largest quantitative signal, but the leaf also can contain speciogynine, paynantheine, speciociliatine, corynantheidine and many less-studied compounds.
“Major alkaloid” therefore means comparatively abundant in the tested plant material. It does not mean only active constituent, only possible source of effects or a fixed percentage in every leaf. For help comparing percent, milligrams per gram, parts per million and reporting limits, see Kiody’s kratom alkaloid-results guide.
| Material | What it represents | Evidence boundary |
|---|---|---|
| Fresh or dried leaf | A variable plant matrix with many alkaloids and non-alkaloid constituents | A measured lot cannot define every plant, season or product |
| Leaf tea | Compounds transferred into water under specific preparation conditions | Not automatically equivalent to swallowed powder or an extract |
| Broad-spectrum extract | A preparation that concentrates or selectively transfers constituents | Its exposure cannot be assumed from an equal weight of leaf |
| Purified mitragynine | One isolated molecule used in receptor, metabolism or animal experiments | Does not reproduce the whole-leaf mixture |
| 7-OH metabolite | 7-OH formed from mitragynine inside the body | Not equivalent to swallowing a high-7-OH product |
| Concentrated or manufactured derivative | A formulation enriched with 7-OH or containing another converted or synthesized compound | Findings cannot be attributed to ordinary botanical leaf |
How much mitragynine is in natural kratom leaf?
There is no universal percentage. Genetics, location, season, leaf maturity, light, fertility, withering, drying and storage can influence a measured result. Laboratory extraction, calibration and chromatography can add another layer of variation.
A 2022 field study measured mitragynine in leaves from naturally growing kratom populations across Thailand and reported a broad range in dry-leaf weight. The researchers also examined environmental variables. That design provides direct evidence of natural variation within the sampled population; it does not define every tree or commercial lot worldwide. Read Leksungnoen and colleagues’ original study.
A separate University of Florida study published in 2025 followed two cultivated kratom varieties through controlled withering, drying and seasonal conditions. Mitragynine changed with postharvest handling, and the pattern differed by cultivar and season. Because only two varieties and defined procedures were studied, the percentages should not be promoted as universal product specifications. The authors reported no commercial financial conflict; one disclosed an editorial-board role. Read Zhang et al., 2025.
The practical conclusion is modest: a lot-specific laboratory result is more informative than a strain name or an internet-wide “typical percentage.” A number also needs a denominator. Percent of dry leaf, percent of a total-alkaloid fraction and percent of an extract are not interchangeable.
Chemistry: why three-dimensional structure matters
Mitragynine belongs to a family of structurally related monoterpene indole alkaloids. Speciogynine, speciociliatine and mitraciliatine share the same molecular formula and basic connectivity but differ in spatial configuration. Chemists call them diastereomers. Those three-dimensional differences can change receptor fit, protein binding, distribution and metabolism.
This is why a mass-spectrometry signal alone may be insufficient when related alkaloids share the same transition. A validated quantitative method needs chromatographic separation and appropriate reference standards. Nuclear magnetic resonance and high-resolution mass spectrometry can help establish identity when researchers isolate a compound. In 2020, Flores-Bocanegra and colleagues used NMR, high-resolution MS and related tools to characterize 19 indole and oxindole alkaloids isolated from two commercial materials. That was a structure-identification study—not a prevalence survey of all leaf. The work was NIH-supported. Read the original chemistry study.
What does mitragynine do at opioid receptors?
Purified mitragynine can bind to and activate the human mu-opioid receptor in cell systems. Multiple studies classify it as a partial agonist under their particular assay conditions: it produces less maximal signaling than the reference full agonist in that system. Its measured affinity, potency and efficacy vary with the cell line, receptor density, signaling readout and comparator.
In a foundational 2016 study, Kruegel and colleagues synthesized and tested mitragynine-family compounds in human opioid-receptor assays. Mitragynine showed partial mu-receptor agonism, while its delta- and kappa-receptor behavior differed from that of classical opioid agonists. The work also reported little measurable beta-arrestin-2 recruitment in its system. Read Kruegel et al., 2016.
A March 17, 2026 study used radioligand binding, cAMP, beta-arrestin-2 and GTP-gamma-S assays across human mu-, kappa- and delta-opioid receptors. In that platform, mitragynine had moderate mu-receptor affinity and functioned as a partial agonist; it also showed weaker kappa-receptor activity. The paper’s numerical values are assay-specific and should not be treated as a dose-response prediction for a person or a leaf product. The experiments used isolated compounds and receptor-expressing cells, not human participants. High Point University and NIH centers funded the work; the authors declared no commercial financial relationships, and one author disclosed a journal editorial-board role. Read Hemby et al., 2026.
Does “G-protein biased” mean “safe”?
No. Some assays show mitragynine favoring G-protein signaling over beta-arrestin-2 recruitment. That is a mechanistic description relative to the assay and comparator. It is not a safety certification.
Researchers continue to debate how much signaling bias, low intrinsic efficacy, metabolism and other targets each contribute to an opioid ligand’s effects. Later work with other opioids has shown that respiratory depression cannot be assigned to one signaling protein alone. Whole-body outcomes also depend on exposure at the receptor, active metabolites, brain circuitry and other substances. “Little beta-arrestin recruitment” should therefore generate hypotheses, not a claim that overdose is impossible.
Mitragynine also interacts with non-opioid systems
Mitragynine is not pharmacologically defined by one receptor. Cell and animal studies report interactions involving adrenergic and serotonergic systems, among others. These findings may help explain why people describe kratom effects that do not fit a simple classical-opioid model, but the human relevance of many targets remains uncertain.
Obeng and colleagues evaluated selected isolated kratom alkaloids for opioid and adrenergic binding, metabolic stability, protein binding and functional effects. That study linked mitragynine-family structure to multiple laboratory measurements; it did not administer leaf to people. Read Obeng et al., 2020.
León and colleagues later tested several isolated alkaloids at serotonin receptors and found that stereochemistry influenced receptor activity. Mitragynine was part of this multi-compound laboratory program, but a receptor interaction is not evidence that kratom treats a psychiatric condition. The study was preclinical and cannot establish a human benefit. Read León et al., 2021.
Metabolism: mitragynine does not remain unchanged
After exposure, enzymes transform mitragynine into multiple metabolites. One important pathway involves CYP3A-mediated oxidation to 7-OH. Kruegel and colleagues demonstrated this conversion in liver microsomes and animal experiments and found that the metabolite contributed strongly to antinociceptive effects in mice. The study supports 7-OH as an active metabolite; it does not prove that every human effect of leaf is caused by 7-OH. Read Kruegel et al., 2019.
The distinction between metabolite and product matters. A person’s body forming a limited amount of 7-OH over time after botanical-leaf exposure is not the same exposure as consuming a tablet, gummy, shot or powder deliberately concentrated or manufactured to contain high 7-OH. Kiody’s botanical kratom versus concentrated 7-OH guide explains that product boundary.
Other metabolic routes include oxidative transformations and conjugation. Their relative importance can differ between liver microsomes, recombinant enzymes, animals and people. Detecting a metabolite does not by itself show how much it contributes to a perceived effect or adverse event.
What early human pharmacokinetic studies show
Pharmacokinetics describes what the body does to a compound: absorption, distribution, metabolism and elimination. It does not by itself establish whether a product is effective or safe for a medical purpose.
In 2022, Tanna and colleagues administered one well-characterized dried-leaf product prepared as tea to six healthy adults. The researchers measured mitragynine and several related alkaloids in plasma and urine. Mitragynine reached its observed peak relatively early and had a longer terminal phase than several 3R diastereomers. Five participants completed the full urine collection. The study was carefully characterized but small, tested one product and one preparation, and was not designed to estimate rare risks. The authors declared no conflicts; NIH/NCCIH funded the work. Read Tanna et al., 2022.
A 2024 randomized, double-blind, placebo-controlled dose-escalation study analyzed mitragynine and 7-OH after single and repeated exposure to one encapsulated dried-leaf powder. The pharmacokinetic analysis included 49 participants who received the active product across four cohorts, with placebo participants in the broader trial. Mitragynine exposure increased with the tested levels, and repeated exposure produced accumulation before steady state. The authors attributed most measured 7-OH exposure to metabolism because the characterized powder contained less than 0.01% 7-OH.
This larger controlled dataset improves the human exposure map, but it has important conflicts and limits. Johnson Foods paid for the clinical study of its MitraLeaf product; all four authors were paid consultants to the company, one was employed by Della Terra Pharmaceuticals, and two disclosed consulting for the American Kratom Association. It remains a study of one sponsor’s standardized leaf powder in healthy volunteers—not proof about every commercial product, people with medical conditions or long-term use. Read Huestis et al., 2024.
| Study | Design and material | What it adds | Main limitation or conflict |
|---|---|---|---|
| Tanna et al., 2022 | Six healthy adults; one characterized dried-leaf product prepared as tea | Plasma and urine pharmacokinetics for mitragynine and several co-occurring alkaloids | Small sample, one product, one exposure; NIH/NCCIH-funded |
| Tanna et al., 2023 | Twelve healthy adults; characterized tea with probe drugs in a crossover assessment | Early clinical evidence of intestinal CYP3A interaction potential | Small sample, single preparation and short observation |
| Huestis et al., 2024 | Randomized, double-blind, placebo-controlled escalation; one encapsulated dried-leaf powder | Single- and repeated-exposure pharmacokinetics for mitragynine and 7-OH | One sponsor product; company-funded; author consulting and employment conflicts |
Interaction science: enzyme inhibition versus a clinical interaction
Purified mitragynine and kratom extracts can inhibit cytochrome P450 enzymes in laboratory systems. The strongest recurring concern involves CYP3A and CYP2D6, but in-vitro inhibition does not automatically mean a clinically important interaction. Intestinal concentration, free concentration, repeated exposure, product composition and the other drug’s therapeutic margin all matter.
In a 2023 crossover study, 12 healthy adults received a characterized kratom tea with the probe drugs midazolam and dextromethorphan. The tea modestly increased systemic exposure to oral midazolam, consistent with intestinal CYP3A inhibition, but did not produce the same pattern for dextromethorphan. That was an early signal, not a complete interaction map. It tested one leaf preparation and two probes in a small, selected sample. The study was NIH/NCCIH-funded, and the authors declared no conflict. Read Tanna et al., 2023.
The appropriate public-health message is not a list of “safe combinations.” People who use medications should discuss kratom with a qualified clinician or pharmacist, especially when a medication affects the central nervous system or has a narrow therapeutic range. Kiody’s interaction evidence guide separates clinical studies, case reports and mechanistic warnings.
Respiratory research: a real distinction with real limits
Available preclinical evidence supports a meaningful distinction between isolated mitragynine and classical full mu-opioid agonists. It does not establish zero risk or a human lethal threshold.
Hill and colleagues compared purified mitragynine and 7-OH in mice. Mitragynine’s respiratory effect reached a ceiling in the tested model, while 7-OH produced dose-dependent respiratory depression. Blocking CYP3A reduced mitragynine’s effects, supporting a role for metabolic conversion. Because these were mouse experiments with isolated compounds, the findings cannot be converted into an amount of leaf that would be “safe,” dangerous or fatal for a person. Read Hill et al., 2022.
Henningfield and colleagues compared oral purified mitragynine with oxycodone in rats. Oxycodone produced clear dose-related respiratory depression in that model; mitragynine did not produce the same dose-related pattern at the tested exposures, although sedative-like effects appeared at the highest tested level. The study was funded by the American Kratom Foundation, and several authors disclosed consulting or advocacy-related relationships. It evaluated an isolate in rats, not botanical leaf in people. Read Henningfield et al., 2022.
NIDA’s current research summary likewise states that neither kratom leaves nor mitragynine generally appear to produce the characteristic respiratory depression of a life-threatening classical-opioid overdose, while laboratory 7-OH can cause naloxone-reversible respiratory depression. NIDA also documents reported adverse effects, dependence, interaction concerns, product variability and unresolved questions. The strongest accurate conclusion is therefore comparative and qualified: mitragynine has shown lower respiratory-depressant liability than classical opioids in several preclinical models. That is not proof that ordinary leaf can never contribute to respiratory trouble or a serious outcome. Review NIDA’s kratom evidence overview.
Dependence and abuse-related evidence
Mitragynine’s partial mu-receptor activity makes dependence an important research question. Animal findings are mixed and depend on the procedure. For example, mitragynine did not maintain self-administration like heroin in one rat model and reduced heroin intake after substitution, while other designs show conditioned or withdrawal-related effects under specific conditions. Purified mitragynine, 7-OH and whole-leaf products should not be collapsed into a single result.
Human observational studies show that some people who use kratom regularly report tolerance, withdrawal and symptoms consistent with a use disorder. Those studies generally cannot assign the outcome to mitragynine alone because participants use multi-constituent products of variable composition. Frequency of use, product type, previous substance exposure and co-use all need consideration.
What a laboratory can measure
Targeted liquid chromatography–tandem mass spectrometry is widely used to quantify mitragynine in leaf products and biological specimens. A defensible result should identify the sample matrix, extraction procedure, reference standard, calibration range, quality controls, reporting unit and measurement limits. Closely related diastereomers must be chromatographically separated when they share mass transitions.
A result labeled “total alkaloids” is not a mitragynine result unless the report defines the measurement. Likewise, “not detected” means below that method’s detection boundary in the tested sample, not that zero molecules exist. For a broader testing checklist, see Kiody’s full-panel kratom COA guide.
Claim check: what the evidence supports
| Claim | Best available evidence | What the evidence does not establish |
|---|---|---|
| “Mitragynine is kratom.” | Mitragynine is usually the predominant alkaloid measured in a chemically diverse leaf. | An isolate does not reproduce botanical leaf. |
| “All natural leaf has the same mitragynine percentage.” | Plant, season, postharvest and analytical studies document variability. | No single percentage defines every lot. |
| “Mitragynine and 7-OH are the same chemical.” | They are distinct compounds; the body can metabolically convert some mitragynine to 7-OH. | Metabolic formation is not equivalent to consuming concentrated 7-OH. |
| “Partial agonist means harmless.” | Partial agonism describes maximal response in a defined receptor assay. | It does not rule out dependence, interactions, impairment or serious adverse effects. |
| “The respiratory studies prove leaf overdose is impossible.” | Several animal studies show lower or ceiling-limited respiratory effects for isolated mitragynine compared with classical opioids. | They do not establish a universal human safety boundary or lethal dose for natural leaf. |
| “Postmortem mitragynine proves natural leaf caused a death.” | Detection establishes that mitragynine was present above the method’s reporting threshold. | It cannot identify the exact product, formulation, timing, impairment or cause without the full case record. |
Why no human lethal amount appears in this guide
There is no validated human lethal dose for ordinary botanical kratom leaf. Converting a rodent dose into kilograms of leaf for a person is not scientifically defensible. Species, route, formulation, absorption, metabolism, alkaloid profile, co-exposures and individual health all change the question. Publishing a guessed “impossible overdose” number would turn uncertain animal data into potentially dangerous human instructions.
The evidence also does not justify the opposite shortcut. A case record that detects mitragynine may involve fentanyl, other opioids, benzodiazepines, alcohol, stimulants, prescription medicines, contaminants, an extract, manufactured 7-OH or an unidentified product. Detection alone does not prove botanical leaf caused the outcome. But incomplete product identification cannot prove that unaltered leaf has zero risk. Careful scientific writing keeps both limits visible.
Research gaps that matter next
- Larger independent human studies using multiple fully characterized botanical-leaf lots.
- Direct comparisons among fresh leaf, dried powder, tea and extracts with matched mitragynine exposure.
- Better measurement of how genetics, season and processing change mitragynine and metabolite exposure.
- Human studies that test interaction signals beyond a small number of probe drugs.
- Respiratory and impairment research in people designed around well-characterized leaf rather than unidentified commercial products.
- Studies of how minor alkaloids modify mitragynine’s receptor activity and metabolism at realistic leaf ratios.
- Transparent replication that reports funding, conflicts, raw data, reference standards and complete product chemistry.
Frequently asked questions
Is mitragynine natural?
Yes. Mitragynine is a naturally occurring alkaloid in Mitragyna speciosa leaf. Purified or synthesized mitragynine used in a laboratory is chemically defined material, not the same research material as a whole leaf.
Is mitragynine the same as 7-hydroxymitragynine?
No. They are distinct compounds. Enzymes can convert some mitragynine into 7-OH after exposure, but that does not make botanical leaf equivalent to a concentrated or manufactured 7-OH product.
Is mitragynine an opioid?
It is often described as an atypical opioid-receptor ligand because purified mitragynine partially activates the mu-opioid receptor and has a signaling profile that differs from classical full agonists. The word does not mean it is identical to morphine, oxycodone or fentanyl.
Does mitragynine affect only opioid receptors?
No. Preclinical studies report adrenergic, serotonergic and other interactions. The human importance of many non-opioid targets is not yet clear.
How long does mitragynine stay in the body?
Human studies show a multi-phase concentration pattern and substantial variability. The measured terminal phase depends on the product, analytical sensitivity, exposure pattern and person. A population estimate is not a personal drug-testing window.
Can mitragynine interact with medications?
Yes, interaction potential cannot be ruled out. Laboratory evidence implicates CYP pathways, and a 12-person study found a modest interaction signal with oral midazolam. That small study does not define every medication combination.
Does mitragynine cause less respiratory depression than classical opioids?
Several animal studies support lower or ceiling-limited respiratory-depressant effects for isolated mitragynine compared with classical full mu-opioid agonists. This is supportive comparative evidence, not proof of universal human safety and not evidence about concentrated 7-OH.
Can an animal study tell us how much natural leaf would be fatal to a person?
No. A rodent-to-human lethal-dose conversion ignores species, route, formulation, metabolism and product-composition differences. There is no validated human lethal amount for ordinary botanical leaf.
Primary evidence trail
- Kruegel AC, et al. Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids. Journal of the American Chemical Society. 2016. Isolated-compound human opioid-receptor assays; no human administration.
- Kruegel AC, et al. 7-Hydroxymitragynine Is an Active Metabolite of Mitragynine. ACS Central Science. 2019. Microsomal and mouse experiments supporting CYP3A-mediated formation and active-metabolite effects.
- Obeng S, et al. Investigation of the Adrenergic and Opioid Binding Affinities, Metabolic Stability, Plasma Protein Binding Properties, and Functional Effects of Selected Indole-Based Kratom Alkaloids. Journal of Medicinal Chemistry. 2020. Isolated-alkaloid receptor, metabolic-stability and protein-binding work.
- Todd DA, et al. Chemical Composition and Biological Effects of Kratom. Scientific Reports. 2020. Fifty-three commercial products plus selected isolated-compound receptor and enzyme assays; NIH-supported; no competing interests declared.
- León F, et al. Activity of Kratom Alkaloids at Serotonin Receptors. Journal of Medicinal Chemistry. 2021. Preclinical receptor pharmacology; not evidence of psychiatric treatment.
- Tanna RS, et al. Clinical Pharmacokinetic Assessment of Kratom. Pharmaceutics. March 2022. Six healthy adults, one characterized leaf product as tea; NIH/NCCIH-funded; no conflicts declared.
- Hill R, et al. Respiratory Effects of Mitragynine Are Limited by Conversion to 7-OH. British Journal of Pharmacology. 2022. Isolated compounds in mice; no human participants.
- Henningfield JE, et al. Respiratory Effects of Oral Mitragynine and Oxycodone. Psychopharmacology. October 2022. Oral isolate comparison in rats; American Kratom Foundation-funded with disclosed consulting and advocacy relationships.
- Leksungnoen N, et al. Variations in Mitragynine Content in Naturally Growing Kratom. Frontiers in Plant Science. October 2022. Field-sampled Thai leaves; composition and environmental associations, not human pharmacology.
- Tanna RS, et al. Clinical Assessment of Kratom Drug-Interaction Potential. Clinical Pharmacology & Therapeutics. 2023. Twelve healthy adults; characterized tea and two probe drugs; NIH/NCCIH-funded; no conflict declared.
- Huestis MA, et al. Human Mitragynine and 7-OH Pharmacokinetics. Molecules. February 23, 2024. Controlled single and repeated exposure to one encapsulated dried-leaf product; industry-funded with author consulting and employment conflicts.
- Zhang M, et al. Kratom Alkaloid Biosynthesis Varies With Postharvest, Genetic and Seasonal Factors. Frontiers in Plant Science. 2025. Two cultivars under controlled postharvest and seasonal conditions.
- Hemby SE, et al. Multifaceted Modulation of Human Opioid Receptors by Kratom Alkaloids. Frontiers in Pharmacology. March 17, 2026. Human-receptor cell assays using purified alkaloids; university and NIH support; no commercial financial conflicts declared.
- National Institute on Drug Abuse. Kratom research overview. Official research summary reviewed September 15, 2026.
Editorial boundary: this guide explains evidence; it does not claim that kratom or mitragynine treats, cures or prevents any condition. It does not provide dosing or overdose instructions. If you take medication, have a health condition, are pregnant or breastfeeding, or experience concerning symptoms, consult a qualified health professional. Do not drive or operate heavy machinery while impaired.