Molecular interactions and behavior of kratom alkaloids-mitragynine, 7-hydroxymitragynine, and mitragynine pseudoindoxylin DPPC lipid bilayers: a molecular dynamics simulation study.

Kratom (Mitragyna speciosa), a tropical plant native to Southeast Asia, has gained global attention for its potential therapeutic effects, particularly as an alternative to classical opioids for pain management and opioid withdrawal. Its primary alkaloids—mitragynine, 7-hydroxymitragynine, and mitragynine pseudoindoxyl— exhibit analgesic properties through partial agonism at u- opioid receptors, with a lower risk of respiratory depression compared to traditional opioids. However, despite its widespread use, kratom remains controversial due to limited clinical data and regulatory concerns which hindered its acceptance in mainstream medicine. To address this gap, we employed molecular dynamics (MD) simulations to investigate the interactions of kratom alkaloids with DPPC lipid bilayers, a model system for biological membranes. The simulations reveal that all three alkaloids exhibit amphiphilic behavior, able to rapidly diffuse into the hydrophobic core and localize near the lipid phosphate groups. The preference position allows the alkaloids for the hydrogen bonding with both lipid headgroups and water molecules at the interface. Mitragynine demonstrates the fastest diffusion into the bilayer, followed by 7-hydroxymitragynine and mitragynine pseudoindoxyl. However, at higher concentrations, molecular aggregation in the aqueous environment delays or prevents penetration of the alkaloids into the bilayer, particularly for 7-hydroxymitragynine. These findings highlight the critical role of molecular assembly in modulating membrane interactions and provide insights into the factors influencing the bioavailability and pharmacological efficacy of kratom alkaloids. This study represents a significant step toward understanding the membrane interactions of kratom alkaloids, offering a foundation for future experimental validation and rational drug design. By elucidating the mechanisms underlying their behavior in lipid bilayers, this study contributes to the growing body of knowledge on kratom's therapeutic potential and safety profile. These insights could inform the development of safer and more effective opioid analogs, addressing the ongoing need for alternatives to classical opioids in pain management and addiction treatment.