For those looking for pain relief, relaxation, or energy, the alkaloids, mitragynine and 7-hydroxymitragynine, are usually the most important elements of the kratom leaf. Mitragynine is present in much higher concentrations than 7-OH-mitragynine – an average of 66% of total alkaloid content versus roughly 2%, respectively (Takayama, 2004). That said, the 7-hydroxy version is about 46 times stronger than mitragynine and up to 20 times more potent than morphine by weight (Matsumoto et al., 1996).
Here’s where it gets a little more complex – please pardon the increased scientific speak for a moment. If you remember anything from chemistry class, you may recall that polarity influences the ability of molecules to pass through lipids. The hydroxy group present in 7-OH-mitra makes it more polar than mitragynine. High polarity means greater difficulty in crossing the blood-brain barrier.
The blood-brain barrier is a natural protection mechanism built into the capillaries inside the brain and designed to keep things like toxins and pathogens out while allowing beneficial substances in, though its accuracy in judgment is not perfect. The lower relative polarity of mitragynine makes it able to cross the blood-brain barrier at a rate around 10 times higher than that of 7-hydroxymitragynine, which is compounded by the former’s superior uptake by the brain (Yusof et al., 2019).
All of a sudden it appears that the actual, real-world comparison between the two chemicals may not be as drastic as previously thought when it all plays out. Unfortunately, there is a major lack of empirical data available detailing in vivo studies involving kratom or its components. The attack on science, knowledge, and credible research launched by the FDA and other agencies has done a great deal to impede the discovery of kratom’s other potential benefits.
Basiliere, S., & Kerrigan, S. (2020). Temperature and pH-Dependent Stability of Mitragyna Alkaloids. Journal of Analytical Toxicology, 44(4), 314–324. https://doi.org/10.1093/jat/bkz103
Takayama, H. (2004). Chemistry and Pharmacology of Analgesic Indole Alkaloids from the Rubiaceous Plant, Mitragyna speciosa. CHEMICAL & PHARMACEUTICAL BULLETIN, 52(8), 916–928. https://doi.org/10.1248/cpb.52.916
Matsumoto, K., Takayama, H., Narita, M., Nakamura, A., Suzuki, M., Suzuki, T., Murayama, T., Wongseripipatana, S., Misawa, K., Kitajima, M., Tashima, K., & Horie, S. (2008). MGM-9 [(E)-methyl 2-(3-ethyl-7a,12a-(epoxyethanoxy)-9-fluoro-1,2,3,4,6,7,12,12b-octahydro-8-methoxyindolo[2,3-a]quinolizin-2-yl)-3-methoxyacrylate], a derivative of the indole alkaloid mitragynine: A novel dual-acting μ- and κ-opioid agonist with potent antinociceptive and weak rewarding effects in mice. Neuropharmacology, 55(2), 154–165. https://doi.org/10.1016/j.neuropharm.2008.05.003
Yusof, S. R., Mohd Uzid, M., Teh, E.-H., Hanapi, N. A., Mohideen, M., Mohamad Arshad, A. S., Mordi, M. N., Loryan, I., & Hammarlund-Udenaes, M. (2019). Rate and extent of mitragynine and 7-hydroxymitragynine blood-brain barrier transport and their intra-brain distribution: The missing link in pharmacodynamic studies: MG and 7-OHMG CNS exposure. Addiction Biology, 24(5), 935–945. https://doi.org/10.1111/adb.12661