Elevated 7-Hydroxymitragynine Levels Found in Products Misbranded as Kratom.

Background: The leaves of Mitragyna speciosa, commonly called kratom, have been consumed for centuries for their energizing and analgesic properties. Kratom has gained popularity in North America with an estimated 16 million American consumers. Recently, a new product has emerged, labelled "kratom extract" but purportedly comprised of high concentrations of 7-hydroxymitragynine, an oxidation product of mitragynine, the primary alkaloid found in kratom.

Objective: 7-hydroxymitragynine, a potent mu-agonist, may pose a serious public health risk. Commercial products labelled as containing 7-hydroxymitragynine were evaluated to determine whether the constituent was present and in what concentration.

Method: The concentrations of 7-hydroxymitragynine and mitragynine were determined by a previously validated HPLC-DAD method, AOAC 2017.14. The chromatographic profiles of products were also compared to authentic kratom leaf.

Results: All products were described on their label as containing "kratom extracts." The concentration of mitragynine ranged from 2.0-6.0 mg/g dry weight, substantially lower than typically found in kratom leaves or extracts. 7-hydroxymitragynine was determined at 22-75 mg/g dry weight, 5-28% higher than label claim. The chromatographic profiles of all products were inconsistent with kratom leaf, having exceptional levels of 7-hydroxymitragynine, lacking the other major naturally occurring alkaloids, and exhibiting peaks not observed in leaf.

Conclusions: The products were verified to contain very high levels of 7-hydroxymitragynine, achievable only by synthetic means. These products differ significantly from authentic native kratom leaf and are not kratom extracts, as labelled, but rather synthetic derivatives that constitute unapproved new drugs being unlawfully marketed. There is an urgent need to differentiate kratom, which has been safely consumed for centuries, from 7-hydroxymitragynine that may pose a significant risk to public health.

Highlights: Traditional kratom leaf is distinguished from products found to contain high concentrations of 7-hydroxymitragynine, only achievable by synthetic means. These unapproved new drugs contained other unidentified constituents, also not present in the native kratom leaf. The presence of concentrated 7-hydroxymitragynine products in the market masquerading as kratom is misleading, unlawful, and potentially dangerous to the public.