Simultaneous quantification of seventeen kratom alkaloids and metabolites in human plasma and its application to clinical pharmacokinetic sample analysis

CONTEXT: Korth, commonly known as kratom, has been used traditionally in Southeast Asia by chewing fresh leaves and brewing decoctions (tea) for its stimulant and sedative-like properties. Despite its widespread use, controlled clinical trials are limited and have monitored mitragynine only or a few other major alkaloids and metabolites. OBJECTIVE: The objective of the study was to develop and validate an ultra performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method for the simultaneous quantification of 12 kratom alkaloids along with 5 metabolites of mitragynine in human plasma. MATERIALS AND METHODS: A sensitive UPLC-MS/MS based bioanalytical method for the simultaneous quantification of kratom alkaloids, including mitragynine, speciogynine, speciociliatine, mitraciliatine, paynantheine, isopaynantheine, corynantheidine, corynoxine-A, corynoxine-B, mitraphylline, speciofoline, and ajmalicine, along with five metabolites of mitragynine, 7-hydroxymitragynine, 9-hydroxycorynantheidine, mitragynine 16-carboxylic acid, mitragynine pseudoindoxyl, and 3-dehydromitragynine in human plasma was developed and validated following FDA guidelines. Chemically unstable metabolites, 7-hydroxymitragynine and 9-hydroxycorynantheidine, were stabilized in human plasma. The bioanalytical method was further used for the analysis of plasma samples collected during a clinical trial involving four regular kratom users. RESULTS: The method was linear over the concentration range of 1-250 ng/mL. A simple protein precipitation method was used to extract analytes. Upon oral administration of kratom products, most of the alkaloids were absorbed quickly and showed peak plasma concentrations within 1-2 h post-dose. DISCUSSION AND CONCLUSIONS: Mitragynine, speciociliatine, mitraciliatine, isopaynantheine, and paynantheine are major circulating alkaloids, with mitragynine 16-carboxylic acid and 9-hydroxycorynantheidine being the major circulating metabolites of mitragynine in plasma upon kratom oral administration.