U.S. flag

An official website of the United States government, Department of Justice.

Temperature and pH-Dependent Stability of Mitragyna Alkaloids

NCJ Number
Journal of Analytical Toxicology Volume: 44 Issue: 4 Dated: 2020 Pages: 314-324
Date Published
11 pages

This study examined the stability of MG, 7-hydroxymitragynine (MG-OH), speciociliatine (SC), speciogynine (SG) and paynantheine (PY).


Mitragynine (MG) is the principal psychoactive alkaloid in kratom. The drug produces a variety of dose-dependent effects that appeal to recreational drug users and individuals seeking therapeutic benefits in the absence of medical supervision. Because of documented intoxications, hospitalizations, and fatalities, MG and other alkaloids from Mitragyna speciosa are of increasing importance to the forensic toxicology community; however, the chemical stability of these compounds has not been thoroughly described. In the current study, the short-term stability of the Mitragyna alkaloids was determined over a range of pH (2–10) and temperature (4–80°C) over 8 hours. Liquid chromatography--quadrupole/time-of-flight mass spectrometry was used to estimate half-lives and identify degradation products where possible. The stability of MG and other alkaloids was highly dependent on pH and temperature. All of the Mitragyna alkaloids studied were acid labile. Under alkaline conditions, MG undergoes chemical hydrolysis of the methyl ester to produce 16-carboxymitragynine. MG-OH was the most unstable alkaloid studied, with significant drug loss at 8 hours experienced at temperatures of 40°C and above. No significant drug losses were observed for MG in aqueous solution (pH 2–10) at 4, 20 or 40°C. Diastereoisomers of MG (SC and SG) demonstrated even greater stability. These findings are discussed within the context of the identification of Mitragyna alkaloids in toxicological specimens. (publisher abstract modified)

Date Published: January 1, 2020