The Kratom-Derived Alkaloid Mitragynine Enhances Cortisol Secretion from a Human Adrenocortical Cell Line.

Kratom is a tropical evergreen tree indigenous to Southeast Asia whose leaves and decoctions have long been used in traditional folk medicine for the relief of pain and enhancement of vitality. In recent years kratom use has increased in the United States, where an estimated 10-15 million people use the herb for the self-management of pain and opioid withdrawal. Kratom leaves contain over 40 active alkaloids, with the most important being mitragynine, 7-hydroxymitragynine and paynantheine. To further explore the possible anti-inflammatory actions of these kratom alkaloids, we examined their effects on cortisol secretion in a human adrenocortical cell line. HAC15 cells were exposed to vehicle or mitragynine, 7-hydroxymitragynine, and paynantheine (10 μM). After 24, 48, 72, and 96 h, cortisol secretion was examined. Basal cortisol secretion was significantly increased by mitragynine at all timepoints, with maximal effect at 96 h (in ng/mL: vehicle, 8.9±1.1; 10 μM mitragynine, 47.3±0.7; n=4). Alternatively, 7-hydroxymitragynine only significantly increased basal cortisol levels at the 96 h timepoint (in ng/mL: vehicle, 8.9±1.1; 10 μM 7-hydroxymitragynine, 17.4±1.2; n=4), while paynantheine only significantly increased basal cortisol levels at the 24 h timepoint (in ng/mL: vehicle, 23.4±1.0; 10 μM paynantheine, 32.8±2.2; n=4). Additional studies are currently being done to characterize effects on cellular viability and concentration responses for each of these kratom alkaloids on cortisol secretion. These data indicate that mitragynine can enhance cortisol secretion in vitro and suggest that such a mechanism may contribute to the possible analgesic actions of kratom in vivo.