Isolation and Analysis of Mitragynine in Kratom Leaves by Chromatography Techniques

Abstract

Mitragynine is the principal active alkaloid in Kratom leaves. In the past, kratom leaves were widely used by Thai people, folk healers and traditional Thai doctors. Later, kratom was classified as a narcotic, causing its development and use to be stagnant. However, kratom has been removed from the list of controlled narcotics under the Narcotics Act in 2021, allowing it to be used more widely. At present, in the process of quality control of kratom leaves and kratom leaf products to meet international standards, it is necessary to use mitragynine as a standard substance, which is expensive and still has to be imported. Therefore, this research aimed to develop an isolation procedure of mitragynine from kratom leaves to replace the import of mitragynine. The extract of kratom leaves was prepared by extracting finely ground kratom leaves with 40% ethanol. The extract was subjected for mitragynine isolation by column chromatography using silica gel (grade 9385) as a stationary phase and chloroform and methanol (with 0.1 N sodium hydroxide) at the ratio of 95:5 as a mobile phase. The collecting fractions from column chromatography were examined for the presence of mitragynine by thin layer chromatography. The fractions containing mitragynine as the major component were combined and mitragynine was further purified by turning it into mitragynine picrate. By using high performance thin layer chromatography (HPTLC) technique, the isolated mitragynine had R_f value that matched with that of the standard mitragynine. In addition, the characterization of mitragynine picrate was also performed by ¹H-NMR spectroscopy, Fourier-transform infrared spectroscopy (FITR) and MALDI-TOF mass spectrometry which provided the physical identity data of mitragynine picrate that have never been reported.