Kratom marketing tends to reduce the plant to a single number: percent mitragynine. But Mitragyna speciosa leaf actually contains more than 40 distinct alkaloids, each with its own receptor activity, natural abundance, and role in the plant’s overall effect. Mitragynine makes up roughly two-thirds of that alkaloid content, but a minor compound called 7-hydroxymitragynine — present at under 2% — punches well above its weight at mu-opioid receptors. [3] Smaller players like speciociliatine, paynantheine, and corynantheidine round out the picture and help explain why whole-leaf kratom doesn’t behave like a simple mitragynine solution. [1]
Knowing the fuller alkaloid picture matters for two reasons. First, it explains why kratom’s effects can’t be predicted from a mitragynine percentage alone. Second, it highlights safety considerations — particularly drug interactions — that anyone using kratom regularly should understand.
What alkaloids are and why kratom has so many
Alkaloids are nitrogen-containing compounds plants produce as secondary metabolites, typically for defense or competitive advantage in their environment. Caffeine, morphine, quinine, and nicotine are all familiar examples from other plants.
Kratom’s alkaloids concentrate in the leaf and mostly belong to the monoterpenoid indole alkaloid family — a chemical class shared with other medically significant plants in the Rubiaceae and Apocynaceae families. [2] The two best-studied kratom alkaloids, mitragynine and 7-hydroxymitragynine, act on opioid and adrenergic receptors, which is largely responsible for kratom’s dose-dependent effects — stimulating at low doses, more sedating and analgesic at higher ones. [1]
Mitragynine: the dominant alkaloid
Mitragynine (C₂₃H₃₀N₂O₄) is by far the most abundant alkaloid in kratom leaf, usually accounting for 60–70% of total alkaloid content, though the exact figure shifts with strain and processing. [1]
It acts as a partial agonist at mu-opioid receptors — the same receptor family targeted by morphine and codeine, though it behaves differently in important ways. [4] Research from Kruegel and colleagues found that mitragynine shows “biased agonism”: it activates G-protein signaling but recruits beta-arrestin-2 much less than classical opioids do. That distinction is associated with a potentially lower risk of respiratory depression compared to full mu-opioid agonists. [1] Mitragynine also engages delta-opioid, adrenergic, and serotonin receptors, which likely accounts for the stimulant-like effects reported at lower doses. [4] A 2022 study by Obeng and colleagues, published in the Journal of Pharmacology and Experimental Therapeutics, compared mitragynine’s mu-opioid and alpha-2 adrenergic activity in rats and found distinct interactive profiles between the two systems — a plausible mechanism behind why low doses of kratom feel stimulating while high doses feel more opioid-like. [10]
The liver metabolizes mitragynine mainly through the CYP3A4 enzyme, and it has a plasma half-life of about 9 hours in humans. [5] That metabolic pathway isn’t just a pharmacokinetic detail — CYP3A4 also processes many prescription drugs, and mitragynine inhibits this enzyme, creating real potential for drug interactions. [6]
Key facts about mitragynine:
- Partial mu-opioid receptor agonist with a biased signaling profile (limited beta-arrestin-2 recruitment) [1]
- Also active at delta-opioid, alpha-2 adrenergic, and 5-HT₂A receptors [4]
- Converted in the body to 7-hydroxymitragynine via hepatic CYP3A4 [3]
- Roughly 9-hour plasma half-life; cleared mainly by the liver [5]
- Inhibits CYP3A4 and CYP2D6, raising drug interaction risk [6]
7-Hydroxymitragynine: small quantity, outsized effect
A note on natural vs. synthetic 7-OH: This section discusses 7-hydroxymitragynine as it naturally occurs in kratom leaf — at under 0.02% by weight — and as the metabolite the liver produces from mitragynine via CYP3A4. It does not cover the separate category of synthetic or semi-synthetic 7-OH concentrate products (tablets, gummies, vapes, infused leaf) that began appearing in the U.S. market around 2023 and are currently facing FDA enforcement action. Those products are chemically and legally distinct from the naturally occurring compound discussed here.
7-Hydroxymitragynine (7-HMG) is an oxygenated form of mitragynine, naturally present in kratom leaf at under 2% of total alkaloid content. Its abundance is small, but its pharmacological importance isn’t. [3]
Kruegel and colleagues showed in 2019 that the liver’s CYP3A4 enzyme generates 7-HMG from mitragynine, and that it may be a key driver of kratom’s pain-relieving effects. [3] In animal studies, 7-HMG showed roughly 13 times the potency of morphine at mu-opioid receptors and crossed the blood-brain barrier more efficiently than mitragynine itself. [1]
This parent-to-metabolite relationship has some practical implications:
- CYP3A4 activity varies from person to person based on genetics, other medications, and liver health — so the amount of 7-HMG someone generates from the same dose of kratom can differ.
- Products deliberately spiked with extra 7-HMG (documented in cases of adulteration) are substantially more potent and carry a higher risk of dependence. [1]
- A lab report showing 7-HMG levels well above the natural baseline (~0.02%) is a warning sign of possible adulteration.
What the minor alkaloids contribute
Beyond mitragynine and 7-HMG, kratom leaf contains roughly 40 other alkaloids, each typically under 1% of total content. [1] Human research on most of these is limited, but their receptor activity has been partially mapped:
Speciociliatine (around 1% of total alkaloids) is a structural mirror-image variant of mitragynine with weaker mu-opioid activity. It may affect gut motility through peripheral opioid receptors, possibly contributing to the constipation some users report at higher doses. [2] A 2022 study by Kamble and colleagues in the AAPS Journal mapped speciociliatine’s metabolic pathways in detail, confirming it’s not the pharmacologically inactive compound it’s sometimes assumed to be. [9]
Paynantheine acts as a smooth muscle relaxant with some adrenergic receptor activity. Its exact role in human effects isn’t well established, but it may contribute to the muscle relaxation some users notice at moderate doses. [2]
Speciogynine is structurally close to speciociliatine and shares similarly weak opioid activity. It likely acts more peripherally, without much central nervous system involvement. [2]
Corynantheidine stands out because some lab studies show it acting as an opioid receptor antagonist — meaning it may partially counteract the agonist effects of mitragynine and 7-HMG rather than add to them. This could help explain why kratom’s subjective effects differ from classical opioids even at comparable receptor occupancy. [1] [7]
Mitraphylline, an oxindole alkaloid also found in cat’s claw (Uncaria tomentosa), has shown immune-modulating and blood-vessel-dilating activity in lab studies, though its role in kratom’s overall effects in humans remains unclear.
Rhynchophylline is unique among kratom alkaloids for its NMDA receptor antagonist activity in lab studies, along with anti-arrhythmic effects seen in animal research. At the trace levels found in kratom, though, its practical contribution is uncertain. [2]
The takeaway: two products with the exact same mitragynine percentage can still feel different, because it’s the entire alkaloid profile — not mitragynine alone — that shapes the overall experience.
Kratom alkaloid reference table
| Alkaloid | Typical Abundance | Primary Receptor Target(s) | Key Notes |
|---|---|---|---|
| Mitragynine | 60–70% | MOR partial agonist; alpha-2 adrenergic; 5-HT₂A; delta-opioid | Biased agonism; converts to 7-HMG via CYP3A4 |
| 7-Hydroxymitragynine | <2% naturally | Full MOR agonist (~13× morphine potency in animal models) | Key analgesic mediator; produced in vivo from mitragynine |
| Speciociliatine | ~1% | Weak MOR agonist; peripheral GI opioid receptors | May contribute to constipation; structural variant of mitragynine |
| Paynantheine | <1% | Smooth muscle relaxant; possible adrenergic activity | May contribute to muscle relaxation |
| Speciogynine | <1% | Weak opioid receptor activity | Related to speciociliatine; mainly peripheral |
| Corynantheidine | <1% | Opioid receptor antagonist (in some models) | May counteract mitragynine/7-HMG agonism |
| Mitraphylline | <1% | Immunomodulatory; vasodilatory | Also found in cat’s claw |
| Rhynchophylline | Trace | NMDA receptor antagonist; anti-arrhythmic (in vitro) | Only kratom alkaloid with known NMDA activity |
Sources: Kruegel & Grundmann 2018 [1]; Hanapi et al. 2021 [2]; Kruegel et al. 2019 [3]. Abundance figures reflect typical HPLC results; individual products vary.
How kratom alkaloids affect drug-metabolizing enzymes
One of the more clinically important findings in kratom research involves cytochrome P450 (CYP) enzymes — the liver’s main system for breaking down drugs. Kong and colleagues (2011) found that kratom alkaloid extract significantly inhibited CYP3A4, CYP2D6, and CYP1A2 in lab assays. [6] Hanapi and colleagues (2021) later confirmed that mitragynine and related alkaloids interact directly with CYP3A4, CYP2D6, CYP2C9, and CYP1A2. [2]
When kratom alkaloids inhibit these enzymes, they can slow the clearance of other drugs a person is taking, raising blood levels and potentially increasing effects or toxicity. Drugs processed through these same pathways include:
- CYP3A4: benzodiazepines, many SSRIs, statins, macrolide antibiotics, immunosuppressants
- CYP2D6: opioid painkillers (codeine, tramadol, oxycodone), many antidepressants, beta-blockers
- CYP1A2: caffeine, theophylline, clozapine, certain antidepressants
This is why anyone taking prescription medication should tell their doctor about kratom use before combining the two. [2]
Why alkaloid profiles differ between products
Alkaloid content isn’t fixed for the species — it shifts based on several factors, which is why the same vendor’s products can vary from batch to batch: [1]
- Harvest maturity. Leaf alkaloid content changes as the plant ages. Vein color (white to green to red) partly tracks this — mature red-vein leaf tends to have higher alkaloid density and a different balance of mitragynine to minor alkaloids than young white-vein leaf. HPLC data confirms real variation across these categories.
- Drying and processing. Sun-drying, indoor fermentation, and blending methods all shift the final alkaloid mix. UV exposure degrades some alkaloids, while fermentation may increase certain oxidized forms. [1]
- Growing conditions. Soil composition, humidity, rainfall, and tree genetics all affect alkaloid yield across Indonesia’s growing regions — Kalimantan, Sumatra, Sulawesi.
- Blending. Many commercial products mix material from multiple sources to smooth out variation. That improves consistency but hides strain-specific data.
This is precisely why batch-specific lab results matter more than strain names. A Certificate of Analysis tied to a specific lot is the only reliable way to know what’s actually in a given product.
Reading a kratom lab report
Reputable vendors provide a Certificate of Analysis (COA) per batch, produced by an independent, accredited lab. Alkaloid content typically appears in two formats — percent by weight and milligrams per gram:
| COA Field | What It Means | Typical Range (Quality Powder) |
|---|---|---|
| Mitragynine % | Mitragynine as % of total powder weight | 1.2–1.8% |
| Mitragynine mg/g | Milligrams of mitragynine per gram of powder | 12–18 mg/g |
| 7-HMG % | 7-hydroxymitragynine as % of powder weight | <0.02% (flag if notably higher) |
| Total Alkaloids % | Combined measurable alkaloid content | 1.5–2.5% |
| Heavy Metals | Lead, arsenic, mercury, cadmium — should meet USP limits | Pass/fail notation |
A mitragynine reading of 1.2–1.8% suggests good-quality plain leaf powder. Anything below 0.8% may point to diluted or lower-potency material. If 7-HMG shows up well above 0.02% in plain-leaf powder, treat it as a red flag — naturally dried leaf rarely exceeds that threshold. [3] A 2026 Phytochemistry study by Avula and colleagues measured 7-HMG levels across a range of commercial kratom products and examined how the compound holds up under storage and physiological conditions. It’s currently the best available benchmark for what natural 7-HMG values should look like — and it supports the guidance above about flagging elevated readings. [11]
Closing thoughts
Kratom’s effects come from an interplay of dozens of alkaloids, not from mitragynine acting alone. Understanding that fuller picture — how mitragynine converts to 7-HMG, what the minor alkaloids do, and how CYP enzyme inhibition creates drug interaction risk — gives a much clearer sense of what a given product is actually delivering. Because alkaloid content shifts with harvest, processing, and blending, a batch-specific lab report remains the most reliable way to know what’s really in the powder in front of you.
References
- Kruegel AC, Grundmann O. The medicinal chemistry and neuropharmacology of kratom. Neuropharmacology. 2018.
- Hanapi NA, et al. Kratom alkaloids: Interactions with enzymes, receptors, and cellular barriers. Front Pharmacol. 2021.
- Kruegel AC, et al. 7-Hydroxymitragynine is an active metabolite of mitragynine and a key mediator of its analgesic effects. ACS Cent Sci. 2019.
- Suhaimi FW, et al. Neurobiology of kratom and its main alkaloid mitragynine. Brain Res Bull. 2016.
- Trakulsrichai S, et al. Pharmacokinetics of mitragynine in man. Drug Des Devel Ther. 2015.
- Kong WM, et al. Evaluation of the effects of Mitragyna speciosa alkaloid extract on cytochrome P450 enzymes. Molecules. 2011.
- Prozialeck WC, Avery BA, Boyer EW, et al. Kratom policy: The challenge of balancing therapeutic potential with public safety. Int J Drug Policy. 2019.
- Hemby SE, McIntosh S, Leon F, et al. Abuse liability and therapeutic potential of the Mitragyna speciosa (kratom) alkaloids mitragynine and 7-hydroxymitragynine. Addiction Biology. 2019;24(5):874-885.
- Kamble SH, et al. Metabolism of speciociliatine, an overlooked kratom alkaloid for its potential pharmacological effects. AAPS J. 2022.
- Obeng S, et al. Interactive effects of µ-opioid and adrenergic-α(2) receptor agonists in rats: pharmacological investigation of the primary kratom alkaloid mitragynine and its metabolite 7-hydroxymitragynine. J Pharmacol Exp Ther. 2022.
- Avula B, et al. Quantitative analysis of 7-hydroxymitragynine in commercial kratom products and its stability under chemical and physiological conditions. Phytochemistry. 2026.
Frequently Asked Questions
How many alkaloids does kratom contain?
Mitragyna speciosa leaf contains more than 40 naturally occurring alkaloids, most from the monoterpenoid indole alkaloid family. The two most studied are mitragynine (roughly two-thirds of total alkaloids) and 7-hydroxymitragynine (under 2%). The rest — including speciociliatine, paynantheine, speciogynine, corynantheidine, mitraphylline, and rhynchophylline — occur in smaller amounts but still shape the plant’s overall pharmacology. [1]
Is mitragynine the same as 7-hydroxymitragynine?
No. Mitragynine is the parent compound and the most abundant alkaloid in the leaf. 7-Hydroxymitragynine (7-HMG) forms when liver enzymes (CYP3A4) convert mitragynine metabolically. Despite making up less than 2% of the leaf’s alkaloid content, 7-HMG is estimated to be about 13 times more potent than morphine at mu-opioid receptors in animal studies, making it a major contributor to kratom’s pain-relieving effects. [3]
What is the “entourage effect” in kratom?
This is the idea that the plant’s many alkaloids work together — sometimes reinforcing, sometimes offsetting each other — to produce effects different from any single compound alone. Evidence pointing this way includes corynantheidine’s possible antagonism of mitragynine’s agonist activity, minor alkaloids contributing muscle-relaxant or calming effects, and reports that isolated mitragynine feels different from whole-leaf kratom at an equivalent dose. It remains a working hypothesis, not an established mechanism. [1]
Does a higher mitragynine percentage mean stronger kratom?
Not necessarily. Mitragynine percentage is only one factor. The full alkaloid profile — including minor alkaloids and the ratio of mitragynine to 7-HMG — shapes the overall effect. Two products with identical mitragynine content but different minor alkaloid mixes can feel quite different. Individual differences in CYP3A4 activity also mean people convert different amounts of mitragynine to 7-HMG from the same dose. [3]
Why does 7-HMG content matter on a COA?
Naturally dried kratom leaf rarely has more than 0.02% 7-HMG by weight. Researchers have documented commercial products with levels far above that — a sign of deliberate adulteration, since higher 7-HMG content sharply increases potency and dependence risk. [8] Any COA showing 7-HMG above roughly 0.1% in a plain-leaf product deserves closer scrutiny. [3]
Can kratom alkaloids interact with medications?
Yes, and this matters clinically. Several kratom alkaloids inhibit CYP3A4, CYP2D6, CYP2C9, and CYP1A2 — enzymes responsible for metabolizing a wide range of prescription drugs. [2] [6] That inhibition can raise blood levels of co-administered medications, increasing their effects or toxicity. Anyone on prescription medication should tell their doctor about kratom use before combining the two.
Do different kratom strains really have different alkaloid profiles?
Yes, though with caveats. Vein color reflects harvest maturity and correlates loosely with alkaloid composition — white vein (younger leaf) tends toward higher mitragynine relative to total alkaloids, while red vein (more mature leaf) usually has greater overall alkaloid density. HPLC data backs up real differences across strain categories. But growing region, soil, drying method, and blending all add further variability, so strain names alone are imprecise predictors. Batch-specific lab data is more reliable. [1]
Which alkaloids cause kratom’s stimulant effects at low doses?
At low doses, the stimulant-like effects come mainly from mitragynine’s activity at alpha-2 adrenergic and 5-HT₂A receptors, not from opioid receptor activation, which becomes more dominant at higher doses. [4] That’s why low-dose kratom can feel like a stimulant — more energy, alertness, focus — while higher doses shift toward sedation and pain relief as opioid activity takes over.
