Identification of the Putative Binding Site of a Benzimidazole Opioid (Etazene) and Its Metabolites at µ-Opioid Receptor: A Human Liver Microsomal Assay and Systematic Computational Study

Krishna Chaturvedi; Isuru Hewamanna; Pankaj Pandey; Washim Khan; Yan-Hong Wang; Amar G. Chittiboyina; Robert J. Doerksen; Murrell Godfrey

doi:10.3390/molecules28041601

Molecules (Feb 2023)

Identification of the Putative Binding Site of a Benzimidazole Opioid (Etazene) and Its Metabolites at µ-Opioid Receptor: A Human Liver Microsomal Assay and Systematic Computational Study

Krishna Chaturvedi,
Isuru Hewamanna,
Pankaj Pandey,
Washim Khan,
Yan-Hong Wang,
Amar G. Chittiboyina,
Robert J. Doerksen,
Murrell Godfrey

Affiliations

Krishna Chaturvedi: Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA
Isuru Hewamanna: Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA
Pankaj Pandey: National Center for Natural Products Research, University of Mississippi, University, MS 38677, USA
Washim Khan: National Center for Natural Products Research, University of Mississippi, University, MS 38677, USA
Yan-Hong Wang: National Center for Natural Products Research, University of Mississippi, University, MS 38677, USA
Amar G. Chittiboyina: National Center for Natural Products Research, University of Mississippi, University, MS 38677, USA
Robert J. Doerksen: Division of Medicinal Chemistry, Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, USA
Murrell Godfrey: Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA

DOI: https://doi.org/10.3390/molecules28041601
Journal volume & issue: Vol. 28, no. 4
p. 1601

Abstract

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The synthetic benzimidazole opioid etazene (which has a 70-times higher analgesic activity than morphine), a recreational drug, has gained popularity as a novel psychoactive substance (NPS) on the illegal/darknet market; however, no experimental information is available at the molecular level on the binding mechanism and putative binding site of etazene and its metabolites at the µ-opioid receptor (MOR). In the present study, we investigated the metabolism of etazene in human liver microsomes using ultra-high-performance liquid chromatography–mass spectrometry (UHPLC–MS). We also explored the possibilities of MOR activation by etazene and its metabolites by studying their binding mechanisms and interaction profiles at an active-state MOR model via molecular docking, binding free energy calculations, and all-atom molecular dynamics (MD) simulations. The putative metabolites of etazene were also predicted using the ADMET Predictor 10.1. The molecular docking studies and free energy calculations showed that etazene and its metabolites (M1, M2, and M5–M7) exhibited strong predicted binding affinity at MOR and showed overlapped binding orientation with MOR-bound agonist BU72, which was co-crystallized in the MOR X-ray crystal structure (PDB ID: 5C1M). MD also confirmed the stability of the MOR–etazene and MOR–M6 complexes. These results suggest that etazene and its metabolites may act as strong MOR agonists, highlighting the necessity of experimental validation. The insights from this study, such as key interactions between etazene and its metabolites and the MOR, will allow authorities to predict potential analogs and clarify the target–protein interactions associated with this illicit substance, granting advanced or rapid reactions to confiscating or banning potential emerging drugs.

Published in Molecules

ISSN: 1420-3049 (Online)
Publisher: MDPI AG
Country of publisher: Switzerland
LCC subjects: Science: Chemistry: Organic chemistry
Website: http://www.mdpi.com/journal/molecules

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