5-Demethoxy-10'-ethoxyexotimarin F, a New Coumarin with MAO-B Inhibitory Potential from Murraya exotica L.

Rutaceae plants are known for being a rich source of coumarins. Preliminary molecular docking showed that there was no significant difference for coumarins in Clausena and Murraya , both of which had high scoring values and showed good potential inhibitory activity to the MAO-B enzyme. Overall, 32 coumarins were isolated from Murraya exotica L., including a new coumarin 5-demethoxy-10'-ethoxyexotimarin F ( 1 ). Their structures were elucidated on the basis of a comprehensive analysis of 1D and 2D NMR and HRMS spectroscopic data, and the absolute configurations were assigned via a comparison of the specific rotations and the ECD exciton coupling method. The potential of new coumarin ( 1 ) as a selective inhibitor of MAO-B was initially evaluated through molecular docking and pharmacophore studies. Compound ( 1 ) showed selectivity for the MAO-B isoenzyme and inhibitory activity in the sub-micromolar range with an IC 50 value of 153.25 ± 1.58 nM (MAO-B selectivity index > 172).