|Jmol-3D images||Image 1|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
In spite of the fact that mitragynine has sometimes been touted and used as a “legal opioid,” few scientific studies have addressed the psychoactive properties of mitragynine.  Most of the available information is based on anecdotal reports and patient experiences. The general subjective effects of mitragynine have been summarized in various reviews and include improved mood and analgesia, with some subjects experiencing relaxation and others stimulation (paradoxical effects).
Mitragynine itself acts primarily via μ-opioid receptors, though its oxidation product mitragynine pseudoindoxyl, acts as an even more potent and selective μ-opioid agonist but with less affinity for δ or κ receptors. Another alkaloid with a major contribution to the μ-opioid activity of the kratom plant is the related compound 7-hydroxymitragynine, which, while present in the plant in much smaller quantities than mitragynine, is a much more potent μ-opioid agonist. The extent to which this minor but more potent mu agonist constituent of the plant contributes to the subjective effects of Kratom consumption is still unclear. 
Mitragynine was isolated in 1907 by D. Hooper, a process repeated in 1921 by E. Field who gave the alkaloid its name. Its structure was first fully determined in 1964 by D. Zacharias, R. Rosenstein and E. Jeffrey.
Dry kratom leaf contains roughly 1-6% mitragynine. A typical dose ranges from 15 mg to 65 mg. A notable distinction between mitragynine and traditional opioids is that mitragynine does not cause hypoventilation (respiratory depression) and therefore does not carry the primary safety risk associated with traditional opioids.
Physically the freebase is a white, amorphous powder. It is soluble in alcohol, chloroform and acetic acid.
- Jansen KL, Prast CJ (1988). "Ethnopharmacology of kratom and the Mitragyna alkaloids". J Ethnopharmacol 23 (1): 115–9. doi:10.1016/0378-8741(88)90121-3. PMID 3419199.
- Raffa RB, Beckett JR, Brahmbhatt VN, et al. Orally active opioid compounds from a non-poppy source. J Med Chem. 2013;56(12):4840-8.
- Jansen KL, Prast CJ. Ethnopharmacology of kratom and the Mitragyna alkaloids. J Ethnopharmacol. 1988;23(1)115-119.
- Suwanlert S. A study of kratom eaters in Thailand. Bull Narc. 1975;27(3):21-27
- Jansen KL, Prast CJ. Psychoactive properties of mitragynine (kratom). J Psychoactive Drugs. 1988;20(4):455-457.
- Shellard EJ. Ethnopharmacology of kratom and the Mitragyna alkaloids. J Ethnopharmacol. 1989;25(1):123-124.
- Adkins JE, Boyer EW, McCurdy CR. Mitragyna speciosa, a psychoactive tree from Southeast Asia with opioid activity. Curr Top Med Chem. 2011;11(9):1165-1175.
- Takayama H, Ishikawa H, Kurihara M, Kitajima M, Aimi N, Ponglux D, Koyama F, Matsumoto K, Moriyama T, Yamamoto LT, Watanabe K, Murayama T, Horie S (April 2002). "Studies on the synthesis and opioid agonistic activities of mitragynine-related indole alkaloids: discovery of opioid agonists structurally different from other opioid ligands". J. Med. Chem. 45 (9): 1949–56. doi:10.1021/jm010576e. PMID 11960505.
- Yamamoto, L. T.; Horie, S.; Takayama, H.; Aimi, N.; Sakai, S.; Yano, S.; Shan, J.; Pang, P. K.; Ponglux, D.; Watanabe, K. (1999). "Opioid receptor agonistic characteristics of mitragynine pseudoindoxyl in comparison with mitragynine derived from Thai medicinal plant Mitragyna speciosa". General pharmacology 33 (1): 73–81. doi:10.1016/S0306-3623(98)00265-1. PMID 10428019.
- Takayama H (August 2004). "Chemistry and pharmacology of analgesic indole alkaloids from the rubiaceous plant, Mitragyna speciosa". Chem. Pharm. Bull. 52 (8): 916–28. doi:10.1248/cpb.52.916. PMID 15304982.
- Kratom (in English), 2014, retrieved 21 April 2014
- Kikura-Hanaji, Ruri; Kawamura, Maiko; Maruyama,Takuro;Kitajima, Mariko; Takayama, Hiromitsu; Goda,Yukihiro (1 July 2009). "Simultaneous analysis of mitragynine, 7-hydroxymitragynine, and other alkaloids in the psychotropic plant "kratom" (Mitragyna speciosa) by LC-ESI-MS". Forensic Toxicology 27 (2): 67–74. doi:10.1007/s11419-009-0070-5. Retrieved 23 June 2013.
- Takayama H.; Maeda M.; Ohbayashi S.; Kitajima M.; Sakai S.-i.; Aimi N. (1995). "The First Total Synthesis of (-)-Mitragynine, An Analgesic Indole Alkaloid in Mitragyna speciosa". Tetrahedron Letters 36 (51): 9337–9340. doi:10.1016/0040-4039(95)02022-H.
- The Malaysian Journal of Analytical Sciences, Vol 15 No 1: A simple and cost effective isolation and purification protocol of mitragynine from Mitragyna speciosa korth (ketum) leaves.