A preliminary assessment of heavy metal (Pb, Cd, and As) contamination in the leaves and cultivation area of Mitragyna speciosa (Korth.) originating from Thailand

Abstract

Kratom (Mitragyna speciosa (Korth.)) is a plant with various therapeutic applications, treating such ailments as chronic pain and diabetes. Its primary alkaloid, mitragynine, exhibits opioid-like effects without respiratory depression; thus, kratom may be used to treat opioid addiction. However, heavy metal contamination can compromise kratom’s safety and quality. This study examined heavy metal contamination (from arsenic [As], cadmium [Cd], and lead [Pb]) in Thai kratom cultivation areas and dried leaves using inductively coupled plasma mass spectrometry (ICP-MS). Mitragynine concentrations in green Thai kratom (GTK) and red Thai kratom (RTK) were also quantified. The analysis revealed that the As, Pb, and Cr levels in kratom leaves were below the safety thresholds, but soil samples showed significantly high As contamination (177.94±1.30 mg/kg). Mitragynine concentrations were higher in GTK (52.68 mg/g _{(Ethanol extract)}) compared with RTK (39.77 mg/g _{(Ethanol extract)}). The findings provide essential information on heavy metal contamination and mitragynine content in kratom leaves and cultivation areas. While safe levels of heavy metals were found in leaves, elevated As concentrations in soil samples raise concerns about long-term contamination risks. The mitragynine content variability between GTK and RTK warrants further investigation to understand its pharmacological and therapeutic implications. This study emphasizes the need for continued kratom research to ensure kratom’s safe and effective use in traditional and modern medicine.