Identification of five mitragyna alkaloids in blood and tissues using liquid chromatography-quadrupole/time-of-flight mass spectrometry

Abstract

Kratom is a botanical drug with psychoactive properties that is increasingly being used recreationally and “therapeutically” in a non-medically supervised setting. Analytical methods for the detection of kratom use in biological matrices are limited in scope. Prevalence of these alkaloids and their metabolites in forensic specimens is not well understood. The purpose of this study was to develop and validate a procedure to identify five Mitragyna alkaloids in blood and tissues using liquid chromatography quadrupole time–of–flight mass spectrometry (LC–Q/TOF–MS). Mitragynine (MG), speciociliatine (SC), paynantheine (PY), speciogynine (SG) and 7-hydroxymitragynine (7-MG-OH) were identified in postmortem blood (n = 40) and liver specimens (n = 20). Mitragyna alkaloids were determined quantitatively using targeted acquisition and metabolites were identified qualitatively using full scan (untargeted) acquisition. The analytical procedure was validated in accordance with published recommendations. Limits of quantitation were 0.5–2 ng/mL for the five targeted alkaloids. Precision, bias, and matrix effects were all within acceptable thresholds. Concentrations of MG in central and peripheral blood were 1–422 ng/mL and 1–412 ng/mL. Liver concentrations of MG ranged from 1450 ng/g. Metabolites of MG (7-MG-OH, 9-O-demethylmitragynine and 16-carboxymitragynine) were also identified in postmortem blood with 7-MG-OH being identified in at least 95% of cases. Interestingly, SC concentrations were frequently identified in excess of MG concentrations. A validated LC–Q/TOF–MS method for the analysis of five Mitragyna alkaloids is described. In addition, minor Mitragyna alkaloids and metabolites can serve as biomarkers of kratom use in blood and tissues.