Last reviewed September 15, 2026. This guide to kratom leaf alkaloids is educational content for adults 21+. It 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: kratom leaf alkaloids form a chemically diverse mixture, not a one-chemical material. Researchers have identified dozens of structurally related alkaloids in Mitragyna speciosa, but the exact count and measured amounts depend on the plant, season, postharvest handling, sample preparation and analytical method. Mitragynine is generally the dominant alkaloid in leaf. Speciogynine, paynantheine and speciociliatine are among the other commonly studied constituents. 7-OH can occur at trace levels in some processed leaf samples and can also be formed from mitragynine during metabolism. Those facts do not make dried leaf equivalent to an isolated or concentrated 7-OH product.
This guide maps the evidence without turning a cell experiment into a human claim or a single laboratory result into a universal leaf specification. For label units and certificate-of-analysis interpretation, use Kiody’s separate guide to reading kratom alkaloid results.
First, define the material
“Kratom” can refer to a living tree, fresh leaves, dried leaf powder, tea, a broad-spectrum extract, an enhanced product or an isolated compound. Those are not interchangeable research materials. The accepted botanical name is Mitragyna speciosa (Korth.) Havil., a member of the coffee family, Rubiaceae, according to Kew’s Plants of the World Online.
| Material | What it contains | What evidence from it can establish | What it cannot establish by itself |
|---|---|---|---|
| Fresh or dried botanical leaf | A variable plant matrix containing many alkaloids and non-alkaloid constituents | Composition of the specific sampled leaf under the stated method | Composition of every leaf lot or every commercial product |
| Leaf tea | Compounds transferred from leaf into water under defined preparation conditions | What was extracted and measured in that preparation | Equivalence to swallowed powder, a resin or a concentrated liquid |
| Broad-spectrum extract | A preparation that concentrates or selectively transfers compounds | Composition and behavior of that characterized extract | Behavior of ordinary leaf or another extract |
| Isolated alkaloid | One purified compound, such as mitragynine or 7-OH | The compound’s activity in the tested assay, species and route | The net effects or safety profile of the whole leaf matrix |
| Enhanced or manufactured product | Added, enriched, converted or synthesized constituents | Only what testing establishes for that specific formulation | What naturally occurs in unaltered leaf |
This distinction is especially important for 7-OH, mitragynine pseudoindoxyl, MGM-15 and MGM-16. A finding about one cannot be silently transferred to another. Kiody’s botanical leaf versus concentrated 7-OH guide covers that boundary in more detail.
How many kratom alkaloids are there?
There is no single permanent count. A 2021 review described approximately 45 identified alkaloids at that time. A 2026 cell-pharmacology paper referred to more than 50 indole and oxindole alkaloids. The number changes as researchers isolate new compounds, resolve stereochemistry, distinguish true plant constituents from processing products and improve analytical methods. Hanapi and colleagues’ 2021 review and Hemby and colleagues’ 2026 study therefore describe evolving research inventories, not a guarantee that every leaf contains every listed compound.
A useful example is the 2020 chemistry study by Flores-Bocanegra and colleagues. The researchers used two commercial kratom products to isolate and characterize 19 indole and oxindole alkaloids with nuclear magnetic resonance, high-resolution mass spectrometry and related structure-elucidation methods. That work strengthened reference identification; it was not a survey of alkaloid prevalence in all kratom leaf. The study reported NIH support and did not report a commercial conflict. Read the original study.
A scientific map of the best-supported kratom leaf alkaloids
| Alkaloid | Why researchers track it | Evidence boundary |
|---|---|---|
| Mitragynine | Usually the predominant measured leaf alkaloid; studied in analytical, metabolism, receptor, animal and early human pharmacokinetic research | Isolated-mitragynine findings do not automatically describe whole leaf |
| 7-hydroxymitragynine (7-OH) | A potent opioid-receptor-active compound in laboratory models and an active metabolite of mitragynine | Trace occurrence in some leaf analyses is not equivalent to enrichment or manufacture |
| Speciogynine | A mitragynine diastereomer measured in leaf products and human plasma research | Human exposure data remain limited to small, characterized-product studies |
| Speciociliatine | Another mitragynine diastereomer with distinct pharmacokinetic and receptor findings | Much mechanistic evidence is preclinical or in vitro |
| Mitraciliatine | A less abundant member of the mitragynine diastereomer set included in early human pharmacokinetic work | Far less human-outcome evidence than for the product mixture |
| Paynantheine | A commonly measured indole alkaloid with analytical, metabolism and early human pharmacokinetic data | Its independent contribution to whole-leaf effects is not established clinically |
| Isopaynantheine | A paynantheine diastereomer measured in the characterized product used in a six-participant human study | One small product-specific study does not define all leaf |
| Corynantheidine | A minor alkaloid included in receptor, enzyme and rat pharmacokinetic studies | Cell and rat results do not prove a human clinical effect |
| Speciofoline | Helped distinguish two chemical groupings in a 53-product analytical study | It showed no measurable binding at the three opioid receptors in that study’s assay; that does not mean biologically inactive everywhere |
| Speciophylline | A 2026 study reported positive allosteric modulation at the human mu-opioid receptor in cells | It is not speciofoline, and an in-vitro allosteric result is not a demonstrated human effect |
| Mitraphylline, corynoxines and ajmalicine | Identified in chemical studies and included in some multi-alkaloid analytical or rat studies | Composition and human pharmacology remain comparatively sparse |
Mitragynine: predominant does not mean solitary
Mitragynine receives the most attention because it is commonly the largest alkaloid signal in leaf and many commercial leaf products. It interacts with the human mu-opioid receptor in cell systems, but it also has reported activity at non-opioid targets. Target binding, functional signaling, animal behavior and human experience are different levels of evidence; none should be substituted for another.
In the 2020 Todd study, mitragynine acted as a partial agonist at the human mu-opioid receptor and favored G-protein signaling over measurable beta-arrestin-2 recruitment under the assay conditions. This is mechanistically interesting, but the experiment used receptor-expressing cells and an isolated compound. It did not measure breathing, impairment, dependence or long-term outcomes in people. The researchers profiled 53 commercial samples by untargeted liquid chromatography–mass spectrometry, then performed receptor and enzyme experiments on selected isolated alkaloids. They reported NIH support and no competing interests. Read Todd et al., 2020.
The National Institute on Drug Abuse summarizes the developing evidence by noting that mitragynine and 7-OH activate mu-opioid receptors but only partially resemble classical opioids, and that neither kratom leaf nor mitragynine appears to produce the characteristic respiratory depression of a life-threatening classical-opioid overdose in available research. NIDA also emphasizes product variability, reported adverse effects, interaction concerns and major evidence gaps. That is a qualified research summary—not proof that every leaf product is universally safe or that a fatal outcome is physically impossible. Review NIDA’s kratom research overview.
7-OH: trace constituent, metabolite and manufactured product are three different questions
7-OH is often discussed as though every mention describes the same exposure. It does not. Researchers may be measuring trace 7-OH in a leaf-derived sample, 7-OH formed from mitragynine during metabolism, purified 7-OH administered in an experiment, or a commercial product deliberately enriched with or manufactured to contain high 7-OH concentrations.
A University of Florida research page states that fresh leaf contains mitragynine while the presence of 7-OH in unprocessed leaf had not been confirmed in the evidence it reviewed. A later 2025 University of Florida plant study detected an average 0.02%–0.04% 7-OH in leaf alkaloid extracts, only in specific seasons and with differences by cultivar. The study tested two cultivars across defined withering, drying and seasonal conditions; it did not establish a universal percentage for all natural leaf. The authors reported no commercial or financial conflicts, while noting that one author was a journal editorial-board member. Read the UF research overview and Zhang et al., 2025.
Metabolism adds another layer. Human and laboratory research shows that CYP3A-mediated metabolism can convert some mitragynine to 7-OH. Formation rate, subsequent metabolism and overall exposure matter. It is therefore inaccurate both to erase 7-OH from the biology of leaf and to treat leaf as if it were a high-concentration 7-OH tablet. Kruegel and colleagues’ metabolism study explains why 7-OH can act as an active mitragynine metabolite.
Diastereomers: same formula, different three-dimensional arrangement
Mitragynine, speciogynine, speciociliatine and mitraciliatine are diastereomers: they share a molecular formula and connectivity pattern but differ in three-dimensional configuration. Paynantheine and isopaynantheine form another related pair. These structural differences can affect absorption, distribution, metabolism and receptor activity.
The first comprehensive human pharmacokinetic study of multiple kratom alkaloids administered one characterized leaf product as tea to six healthy adults. It found different concentration-time behavior between the study’s 3S alkaloids—mitragynine, speciogynine and paynantheine—and 3R alkaloids including speciociliatine, mitraciliatine and isopaynantheine. Five participants completed the full urine collection. This was a carefully characterized early study, not a population safety trial, not a study of concentrated 7-OH and not proof that every commercial product behaves the same way. The authors declared no conflicts, and NIH/NCCIH supported the work. Read Tanna et al., 2022.
What the newer receptor research adds
A March 17, 2026 study expanded cell-based testing across human mu-, kappa- and delta-opioid receptors. It integrated radioligand binding, cAMP, beta-arrestin-2, GTP-gamma-S and molecular-docking approaches. The researchers reported diverse profiles among isolated indole and oxindole alkaloids, including partial agonism, mixed agonist–antagonist behavior and, for speciophylline, positive allosteric modulation at the human mu-opioid receptor without direct orthosteric binding in that system.
The appropriate conclusion is narrow: the alkaloids are pharmacologically diverse in the tested human-receptor cell models. The study had no human participants and did not administer leaf. It cannot establish a clinical benefit, a human risk threshold or the net effect of a whole-leaf mixture. Funding came from High Point University and NIH centers; the authors declared no commercial financial conflicts, and one author disclosed an editorial-board role. Read Hemby et al., 2026.
Receptor activity is only one part of the system
A receptor-binding result answers whether a compound associates with a receptor under defined experimental conditions. A functional assay asks whether it changes a signaling readout. Neither alone tells us how much compound reaches the brain after a particular leaf product, what metabolites form, how long exposure lasts, how other alkaloids interact or what a person will experience.
That is why phrases such as “binds to,” “activates,” “partially activates,” “antagonizes” and “allosterically modulates” should not be collapsed into the generic claim “does the same thing as an opioid.” Even within the opioid-receptor family, activity can differ by receptor subtype, signaling pathway, species and experimental system.
Metabolism and pharmacokinetics: the body changes the exposure
Researchers have reported phase I and phase II metabolites for mitragynine, speciogynine, paynantheine, speciociliatine, mitraciliatine and isopaynantheine. The 2021 Hanapi review explains that the metabolic map remains incomplete and draws from human urine, rat studies, liver microsomes and recombinant enzymes. Those sources answer different questions. A metabolite detected in urine does not by itself establish its contribution to an effect. Read the review’s metabolism section.
A separate rat study compared the pharmacokinetics of 11 alkaloids after oral administration of a lyophilized traditional tea and a commercial liquid product. Mitragynine, 7-OH, speciociliatine and corynantheidine remained detectable longer than several other measured alkaloids, and normalized exposures differed by formulation. Its value is comparative and mechanistic. Its limitation is equally important: rats are not humans, and the two characterized preparations do not represent every tea, powder or extract. Read Kamble et al., 2021.
Drug-metabolizing enzymes and interaction evidence
Several kratom alkaloids inhibit cytochrome P450 enzymes in vitro. These experiments help researchers decide which interactions deserve clinical testing, but a high-concentration microsomal result is not automatically a clinically important interaction. The relevant questions include intestinal versus hepatic exposure, free concentration, repeated use, product composition and the other drug’s therapeutic margin.
The safest reader-facing conclusion is that interaction risk cannot be ruled out, especially with medications or substances that affect the central nervous system or depend on CYP pathways. Do not use a compound chart to self-manage a medication combination. Kiody’s kratom interactions guide explains the difference between mechanistic signals, small human studies and case reports.
Why alkaloid percentages vary
Variation can begin before a sample reaches a laboratory. Genetics, season, leaf age, growing conditions, withering, drying and storage can change the measured profile. Extraction solvent, particle size, calibration standards, chromatography and data-processing rules can then change what the laboratory detects and quantifies.
The 2025 UF study directly demonstrated effects of cultivar, season and postharvest treatment in its two-cultivar design. The 53-product Todd study found two chemical groupings distinguished partly by speciofoline. Together they show why “green,” “red,” “white” or a geographic marketing name should not be treated as a standardized pharmacological fingerprint. A current lot-specific result is more informative than a strain stereotype.
How to read an alkaloid result without overclaiming
- Match the lot. A report for another batch does not characterize the package in hand.
- Identify the matrix. Leaf powder, tea, extract and finished enhanced products are different.
- Check the method. Targeted LC-MS/MS, untargeted metabolomics and quantitative NMR answer different questions.
- Check the unit. Percent, milligrams per gram and alkaloid-fraction percentages cannot be compared without correct conversion and denominator.
- Find LOD and LOQ. “Not detected” means below a method’s detection boundary, not absolute zero.
- Look for named reference standards. Closely related diastereomers can share mass transitions and require chromatographic separation.
- Separate measurement from meaning. A concentration is not an effect, safety or medical-efficacy claim.
Five claims the evidence does not support
| Claim | Best available correction | What remains unknown |
|---|---|---|
| “Kratom leaf contains only one active chemical.” | Dozens of indole and oxindole alkaloids have been identified; several show distinct activity in laboratory assays. | The contribution of each minor alkaloid to whole-leaf human effects. |
| “7-OH is either absent from all leaf or present at one fixed percentage.” | Fresh unprocessed leaf evidence and processed leaf analyses are not identical; a 2025 study found trace 7-OH only in specific seasons and cultivars. | A universal natural-leaf range across origins and processing conditions. |
| “An opioid-receptor result proves the leaf acts just like fentanyl or oxycodone.” | Kratom alkaloids show distinct affinity, efficacy and signaling profiles, and the whole-leaf mixture differs from an isolated pharmaceutical or illicit opioid. | How all constituents combine across real-world leaf products and people. |
| “A favorable animal or cell result proves natural leaf cannot cause serious harm.” | Preclinical findings can support hypotheses, including potentially lower respiratory-depressant liability for mitragynine than classical opioids, but they do not prove universal human safety. | Individual susceptibility, interactions, product identity and long-term outcomes. |
| “A rodent dose can be converted into the amount a person would need for a fatal overdose.” | Species, route, formulation, metabolism and endpoint differences make such a conversion scientifically invalid and potentially dangerous. | There is no validated human lethal-dose threshold for ordinary botanical leaf. |
What lower respiratory-depressant findings do—and do not—mean
Some preclinical studies and NIDA’s current research summary support a meaningful distinction between mitragynine or ordinary leaf and classical full mu-opioid agonists. That evidence is relevant to responsible-access discussions. It does not establish that natural leaf can never contribute to respiratory problems, impairment or a serious outcome. It also cannot be transferred to concentrated 7-OH or other manufactured derivatives.
No responsible scientific article should publish a guessed human lethal amount or a rodent-to-human fatal-dose conversion. Human outcomes depend on formulation, alkaloid content, co-exposures, health conditions, metabolism and product identity. When case reports or surveillance records do not chemically verify an unaltered leaf product, they cannot answer a leaf-specific causation question. The reverse is also true: incomplete case identification cannot prove zero risk.
Research gaps that matter most
- Larger human pharmacokinetic studies using multiple independently characterized leaf lots.
- Direct comparisons of fresh leaf, dried powder and traditional tea under documented preparation conditions.
- Validated methods that separate closely related diastereomers and report measurement uncertainty.
- Human interaction studies that connect in-vitro enzyme findings to clinically meaningful outcomes.
- Studies of how minor alkaloids modify mitragynine and 7-OH activity in realistic leaf ratios.
- Longitudinal human research separating ordinary leaf from extracts and manufactured high-7-OH products.
- Transparent reporting of source material, funding, conflicts and complete chemical characterization.
Frequently asked questions
Is mitragynine the only alkaloid in kratom leaf?
No. It is generally the predominant measured leaf alkaloid, but dozens of indole and oxindole alkaloids have been identified.
Is 7-OH naturally present in kratom leaf?
The answer depends on how “leaf” and “present” are defined. University of Florida’s research overview says 7-OH had not been confirmed in fresh unprocessed leaf. A 2025 controlled plant study detected trace 7-OH in leaf alkaloid extracts only under certain seasonal and cultivar conditions. Neither finding makes ordinary leaf equivalent to a concentrated or manufactured 7-OH product.
Does the body convert mitragynine into 7-OH?
Yes, laboratory and human evidence supports 7-OH as an active metabolite of mitragynine. Formation and subsequent metabolism are only part of total exposure and should not be equated with ingesting isolated 7-OH.
Are speciogynine and speciociliatine the same as mitragynine?
They are closely related diastereomers, not the same molecule. Their three-dimensional configurations differ, and early research shows differences in pharmacokinetics and receptor behavior.
Do all kratom alkaloids activate opioid receptors?
No. The tested alkaloids show diverse profiles. For example, speciofoline showed no measurable binding at mu-, delta- or kappa-opioid receptors in the 2020 Todd study’s assay, while other compounds showed agonist, antagonist or allosteric behavior in later cell research.
Does G-protein-biased signaling prove an alkaloid is safe?
No. It is a mechanistic finding from specific assays. Signaling bias can guide research, but it does not by itself establish respiratory, dependence or overall safety in humans.
Can a COA predict how a kratom product will affect someone?
No. A COA can report what was measured in a sampled lot under a stated method. It cannot predict an individual response or rule out every contaminant, interaction or health risk.
Can rat toxicology establish a human lethal amount of natural leaf?
No. Direct rodent-to-human lethal-dose conversions ignore species, route, formulation and metabolic differences. This guide does not provide overdose instructions or an unsupported human lethal threshold.
Primary research and review trail
- Flores-Bocanegra L, et al. The Chemistry of Kratom. Journal of Natural Products. July 2020. Chemistry and structure-characterization study using two commercial products; 19 alkaloids characterized; NIH-supported.
- Todd DA, et al. Chemical composition and biological effects of kratom. Scientific Reports. November 2020. Fifty-three commercial products profiled; selected isolated alkaloids tested in human-receptor and enzyme systems; NIH-supported; no competing interests declared.
- Hanapi NA, et al. Kratom Alkaloids: Interactions With Enzymes, Receptors, and Cellular Barriers. Frontiers in Pharmacology. November 2021. Review that clearly separates metabolic, receptor, enzyme and barrier evidence.
- Kamble SH, et al. Pharmacokinetics of Eleven Kratom Alkaloids. Journal of Natural Products. 2021. Oral rat comparison of a traditional tea preparation and commercial liquid product; NIH-supported.
- Tanna RS, et al. Clinical Pharmacokinetic Assessment of Kratom. Pharmaceutics. March 2022. Six healthy adults, one characterized leaf product prepared as tea; NIH/NCCIH-supported; no conflicts declared.
- Zhang M, et al. Alkaloid biosynthesis in medicinal crop kratom varies with postharvest, genetic, and seasonal factors. Frontiers in Plant Science. September 2025. Two cultivars, controlled withering and drying, two seasons; no commercial conflicts declared.
- Hemby SE, et al. Multifaceted modulation of human opioid receptors by kratom alkaloids. Frontiers in Pharmacology. March 17, 2026. Isolated-compound human-receptor cell assays; High Point University and NIH support; no commercial conflicts declared.
- National Institute on Drug Abuse. Kratom research overview. Official research summary reviewed for this article on September 15, 2026.
Editorial boundary: this article describes evidence, not medical effectiveness or a recommendation to use kratom. If you take medications, 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.