What is Mitragynine?

What is Mitragynine? Composition, Structure, and Mechanism of Action

Mitragynine is the major indolic alkaloid found in the leaves of Mitragyna speciosa Korth. Havil. (Rubiaceae), commonly referred to as kratom. It serves as the reference compound for the characterization and standardization of the plant material of this species and is the most studied among the over 40 alkaloids identified in the plant. This article describes its chemical structure, documented mechanism of action, natural concentration in the leaf, and verified analytical data from the Edabea catalog. For historical, ethnobotanical context, and strains of kratom, you may refer to our comprehensive kratom guide. If you're interested in cultivating the plant, you can also check our article on how to cultivate kratom from seeds.

Chemical Classification and Molecular Structure

Mitragynine (C₂₃H₃₀N₂O₄) is a monoterpenoid indolic alkaloid — an indoloquinolizidine — with a complex structural core that includes a fused ring system containing two nitrogen atoms. It was first isolated by Field in 1921, and its chemical structure was established by Zacharias et al. in 1964 (Shellard, E.J. et al., 1978. Planta Medica, 34(3), 253–263).

It shares the indolic core with other alkaloids found in the plant — particularly with 7-hydroxymitragynine, paynantheine, and speciogynine — but the three-dimensional arrangement of its functional groups determines its differential affinity for opioid receptors. Its lipophilic nature facilitates crossing the blood-brain barrier following oral absorption.

Natural Concentration in Mitragyna speciosa Leaves

Mitragynine is the most abundant alkaloid in the dried leaves of Mitragyna speciosa, typically representing between 60% and 70% of the total alkaloid content in the mature leaf (Shellard, E.J. et al., 1978, op. cit.). Absolute concentrations usually range between 1% and 2% of the dry weight of the leaf, with documented variations depending on geographical origin, leaf age at harvest, climatic conditions, and drying processes.

As a reference for the analytical data used in the Edabea catalog, batch 22.885 (October 2025, expiration April 2028) recorded the following analytical values via UHPLC-DAD in an ISO 17025 accredited laboratory (ref. L440):

These data correspond to a specific batch and serve as a reference for the analytical standard applied, not as a uniform guarantee for all batches or varieties. Alkaloid composition varies between batches, origins, and varieties.

Main Alkaloids of Mitragyna speciosa

Mitragyna speciosa contains over 40 identified alkaloids. The four most studied and pharmacologically relevant are:

Mitragynine: the predominant alkaloid, comprising 60–70% of the total alkaloid content. Partial agonist of mu and kappa opioid receptors, with additional documented affinity for adrenergic and serotonergic receptors.

7-hydroxymitragynine: present in very low concentrations in fresh leaf (<0.01% in the analyzed batches), but with significantly higher affinity for mu opioid receptors than mitragynine. Its concentration may increase with processing and storage of the plant material (Matsumoto, K. et al., 2004. Life Sciences, 74(17), 2143–2155).

Paynantheine: second most abundant alkaloid in many varieties. Mu opioid receptor antagonist based on in vitro studies.

Speciogynine: third most abundant alkaloid in analyzed varieties. Mu opioid receptor antagonist based on in vitro studies, possibly having activity on serotonin receptors.

Documented Mechanism of Action

Mitragynine primarily acts as a partial agonist of mu (MOR) and kappa (KOR) opioid receptors in the central nervous system. Unlike classical opioids — morphine, oxycodone — which are full agonists at the mu receptor, mitragynine is a partial agonist, implying submaximal receptor activation even at saturating concentrations. This partial behavior is pharmacologically relevant because it is associated with profiles of effects and tolerance different from those of full agonists (Matsumoto, K. et al., 2004, op. cit.).

Experimental studies have also documented interaction with:

Alpha-2 adrenergic receptors: activation of these presynaptic receptors modulates the release of norepinephrine, which may contribute to the pharmacological profile of the plant.

Serotonergic receptors: activity has been documented on 5-HT2A and 5-HT7 receptors, although to a lesser extent than on opioids.

The combination of these mechanisms explains the complexity of the pharmacological profile of Mitragyna speciosa and why it cannot be simplified as equivalent to a classical opioid.

Documented Pharmacological Effects in Humans

The effects of Mitragyna speciosa in humans have been described both in ethnobotanical literature on traditional use as well as in survey studies and a limited number of clinical studies. The documented profile presents a characteristic that distinguishes it from classical opioids: dose dependency with qualitatively different effects depending on the amount administered. At low doses, users report stimulating effects — increased alertness, reduced fatigue — consistent with the documented alpha-2 adrenergic activity. At higher doses, sedating and analgesic effects predominate, consistent with mu opioid agonism (Veltri, C. & Grundmann, O., 2019. Substance Abuse and Rehabilitation, 10, 23–35).

The analgesic effects of mitragynine have been documented in animal models with nociceptive pain and are the most consistently referenced traditional use in ethnobotanical literature among agricultural workers in Southeast Asia (Matsumoto, K. et al., 2004, op. cit.). The antinociceptive activity is attributed mainly to mu agonism, modulated by the mu antagonism of paynantheine and speciogynine, contributing to a ceiling effect distinct from classical opioids.

Documented adverse effects in users include nausea, constipation, sweating, and, with prolonged use, physical dependence with mild-moderate withdrawal syndrome — similar to that of opioids but of lesser intensity in most reported cases. Psychological dependence is also documented. These risks are relevant for the complete evaluation of the pharmacological profile of the plant and are subject to ongoing regulatory debates regarding its legal status in different jurisdictions.

Relationship between Mitragynine and 7-Hydroxymitragynine

7-Hydroxymitragynine (7-OH) is the most pharmacologically interesting active metabolite of Mitragyna speciosa. Although present in very low concentrations in the leaf (<0.01% in the analyzed batches from the Edabea catalog), its affinity for mu opioid receptors is significantly higher than that of mitragynine. Some preclinical studies suggest that it may form in vivo as a metabolite of mitragynine, although this point remains under investigation.

The relationship between the two compounds is relevant for interpreting the full pharmacological profile of the plant: plant material with a higher concentration of mitragynine does not necessarily imply greater activity on mu receptors, as 7-OH — present in trace amounts — has a much higher relative potency per unit mass.

Concentration Differences Between Varieties and Veins

The various commercial classifications of kratom — by vein color (red, green, white, yellow) and geographical origin (Bali, Borneo, Sumatra, Thailand, Vietnam) — present documented alkaloid profiles with variations that are not precisely predictable among different batches (Veltri, C. & Grundmann, O., 2019. Substance Abuse and Rehabilitation, 10, 23–35).

All varieties in the Edabea catalog belong to the same botanical species — Mitragyna speciosa. The differences between veins are primarily due to the drying and curing post-harvest process, not from profound genetic variation between plants. For a detailed description of each vein and its subcategories, refer to the Edabea kratom catalog.

Analytical Methods for Quantifying Mitragynine

The most commonly used instrumental methods for the quantification and characterization of mitragynine are:

UHPLC-DAD (Ultra High-Performance Liquid Chromatography with Diode Array Detection): the standard method for quantifying the complete alkaloid profile — mitragynine, 7-OH, paynantheine, speciogynine — in the plant material. This method is used in the lot analyses of the Edabea catalog.

ICP-MS (Inductively Coupled Plasma Mass Spectrometry): for quantifying heavy metals (arsenic, cadmium, mercury, lead) in the plant material. Included in the analytical protocol of the Edabea catalog.

GC-MS/MS (Gas Chromatography with Tandem Mass Spectrometry): for detecting pesticide residues according to the standard EN 15662. Included in the analytical protocol of the Edabea catalog, performed in an ISO 17025 accredited laboratory (ref. L440).

Stability and Conservation

The stability of mitragynine in dried plant material is conditioned by the same factors affecting any indolic alkaloid: exposure to UV light, humidity, temperature, and oxidation from contact with air. The material should be stored in a sealed airtight container, protected from direct light and heat. Proper storage preserves the stability of the alkaloid profile throughout the lot validity period.

Current Research Status

Research on mitragynine is currently in preclinical and experimental phases. There are no approved therapeutic indications for human use. Available studies are primarily in vitro and in animal models, with a limited number of studies involving humans. The published literature mainly covers partial agonism at opioid receptors, adrenergic and serotonergic neurotransmission, and comparative analysis between mitragynine and 7-hydroxymitragynine regarding their affinity and relative potency on mu receptors.

Legal Status

The legal status of Mitragyna speciosa and its alkaloids varies by jurisdiction. It is the buyer's responsibility to verify applicable laws in their place of residence before placing an order. This product is marketed solely as botanical collection material and for ethnobotanical research.

Frequently Asked Questions About Mitragynine

Is mitragynine an opioid?

Mitragynine acts on mu and kappa opioid receptors, much like classical opioids, but as a partial agonist — not a complete agonist. This difference is pharmacologically relevant: a partial agonist produces submaximal receptor activation even at saturating concentrations, which is associated with distinct profiles of effects compared to full agonists like morphine. Its chemical structure is also completely different from that of opioids derived from the opium poppy (Papaver somniferum).

Do all kratom varieties contain mitragynine?

Yes — mitragynine is the predominant alkaloid in all commercial varieties of Mitragyna speciosa, regardless of vein color or geographical origin. Concentrations vary among batches and varieties — data from batch 22.885 show 1.37% in Green Maeng Da and 1.22% in White Bali — but mitragynine is always the predominant alkaloid. Differences between veins are mainly due to the drying process, not the absence or presence of mitragynine.

What is the difference between mitragynine and 7-hydroxymitragynine?

They are structurally related compounds — 7-OH is a hydroxylated derivative of mitragynine — but with distinct pharmacological profiles. Mitragynine is present at concentrations of 1–2% of the dry weight of the leaf and acts as a partial agonist at mu and kappa opioid receptors. 7-OH is present at very low concentrations (<0.01% in the analyzed batches) but has a significantly higher affinity for mu receptors than mitragynine. 7-OH may also form as a metabolite of mitragynine in vivo, although this point is still under investigation.

Why does the concentration of mitragynine vary between batches?

Due to multiple agronomic and processing factors: the age of the leaf at harvest, the geographical origin of the plant, climatic conditions during cultivation, and the drying and post-harvest storage process. The vein — red, green, white, yellow — mainly influences through the drying process, which can modify the relative proportions of alkaloids. To ensure consistency in the alkaloid profile, Edabea subjects new batches to laboratory analyses before adding them to the catalog.

What is the purpose of UHPLC-DAD analysis in kratom control?

Ultra High-Performance Liquid Chromatography with Diode Array Detection (UHPLC-DAD) allows for precise quantification of each individual alkaloid — mitragynine, 7-OH, paynantheine, speciogynine — in the analyzed plant material. It is the industry standard method for characterizing the alkaloid profile of kratom because it can separate and identify compounds with similar molecular structures that other, less resolutive methods do not distinguish as accurately.

About This Content

Article prepared by the specialized team at Edabea Natura, with over 15 years of experience in the selection and marketing of ethnobotanical materials. The phytochemical and pharmacological information is based on the cited bibliographic sources. The analytical data from batch 22.885 correspond to analyses conducted using UHPLC-DAD in an ISO 17025 accredited laboratory (ref. L440). Last updated: April 2026.

Bibliographic References

• Matsumoto, K. et al. (2004). Central antinociceptive effects of mitragynine in mice: contribution of descending noradrenergic and serotonergic systems. Life Sciences, 74(17), 2143–2155.
• Shellard, E.J. et al. (1978). The Mitragyna species of Asia. Planta Medica, 34(3), 253–263.
• Veltri, C. & Grundmann, O. (2019). Current perspectives on the impact of Kratom use. Substance Abuse and Rehabilitation, 10, 23–35.