Affiliations 

  • 1 Advanced Medical & Dental Institute, Universiti Sains Malaysia, SAINS@BERTAM, Kepala Batas, Pulau Pinang, Malaysia
  • 2 Malaysian Institute of Pharmaceuticals & Nutraceuticals, National Institutes of Biotechnology Malaysia (NIBM), Ministry of Energy, Science, Technology, Environment and Climate Change (MESTECC), Georgetown, Pulau Pinang, Malaysia
  • 3 Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Georgetown, Pulau Pinang, Malaysia
  • 4 Atta-ur-Rahman Institute for Natural Product Discovery, Universiti Teknologi MARA (UiTM), Shah Alam, Selangor Darul Ehsan, Malaysia
  • 5 School of Biological Sciences, Universiti Sains Malaysia, Penang, Pulau Pinang, Malaysia
  • 6 Pharmaceutical Drug Simulation Laboratory (PhDS), School of Pharmaceutical Sciences, Universiti Sains Malaysia, Georgetown, Pulau Pinang, Malaysia
  • 7 Advanced Medical & Dental Institute, Universiti Sains Malaysia, SAINS@BERTAM, Kepala Batas, Pulau Pinang, Malaysia. tanml@usm.my
Naunyn Schmiedebergs Arch Pharmacol, 2019 04;392(4):481-496.
PMID: 30604191 DOI: 10.1007/s00210-018-01605-y

Abstract

Mitragynine is a major component isolated from Mitragyna speciosa Korth or kratom, a medicinal plant known for its opiate-like and euphoric properties. Multiple toxicity and fatal cases involving mitragynine or kratom have been reported but the underlying causes remain unclear. P-glycoprotein (P-gp) is a multidrug transporter which modulates the pharmacokinetics of xenobiotics and plays a key role in mediating drug-drug interactions. This study investigated the effects of mitragynine on P-gp transport activity, mRNA, and protein expression in Caco-2 cells using molecular docking, bidirectional assay, RT-qPCR, Western blot analysis, and immunocytochemistry techniques, respectively. Molecular docking simulation revealed that mitragynine interacts with important residues at the nucleotide binding domain (NBD) site of the P-gp structure but not with the residues from the substrate binding site. This was consistent with subsequent experimental work as mitragynine exhibited low permeability across the cell monolayer but inhibited digoxin transport at 10 μM, similar to quinidine. The reduction of P-gp activity in vitro was further contributed by the downregulation of mRNA and protein expression of P-gp. In summary, mitragynine is likely a P-gp inhibitor in vitro but not a substrate. Hence, concurrent administration of mitragynine-containing kratom products with psychoactive drugs which are P-gp substrates may lead to clinically significant toxicity. Further clinical study to prove this point is needed.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.