Deploying the drug repurposing approach for the identification of selective monoamine oxidase-B inhibitors against neurological disabilities: an in Silico and in vitro approach

Monoamine oxidase-B (MAO-B) plays a regulatory role in controlling the activity of monoamine neurotransmitters, especially dopamine. Its overexpression leads to a decreased concentration of dopamine in the brain, converts MPTP to MPP + (a potential toxin for dopaminergic neurons), and increases hydrogen peroxide and ROS levels in gliosis, leading to neurodegeneration. Thus, MAO-B becomes a key target enzyme for neurological disabilities such as PD and AD. In this study, we used drug repurposing to explore the pool of USFDA-approved and Pharmacopeial drugs (3619 drugs) and performed HTVS (high-throughput virtual screening) using both ADME parameters with emphasis on their ability to cross the BBB and considering the prerequisites of a generated pharmacophore model for MAO-B. The fetched 656 ligands were subjected to SP and XP dockings, MMGBSA, and dynamics analysis to identify the top 10 leads with maximum plausibility to interact with MAO-B. The analysis presented Bazedoxifene and Epicatechin as lead compounds with a higher affinity towards MAO-B than MAO-A. The in-silico work was further validated using in vitro biological analysis that includes MAO inhibitory activity, reversibility studies, and intracellular ROS inhibition studies. Epicatechin and bazedoxifene displayed moderate MAO-B inhibitory activities with IC₅₀ values of 11.14 ± 0.53 µM and 13.11 ± 0.21 µM, with more than sixfold and fourfold selectivity over MAO-A, respectively. Thus, this study can open the avenue to the development of Bazedoxifene and Epicatechin as potential pharmacophores for the design and development of selective and reversible MAO-B inhibitors with higher efficacy for the management of neurological disabilities.