Semi-synthesis, α-amylase Inhibition, and Kinetic and Molecular Docking Studies of Arylidene-based Sesquiterpene Coumarins Isolated from Pomel Ex Batt

Despite all the significant progresses made to enhance the efficacy of the existing bank of drugs used to manage and cure type II diabetes mellitus, there is still a need to search and develop novel bioactive compounds with superior efficacy and minimal adverse effects. This study describes the valorization of the natural bioactive sesquiterpene coumarin the semi-synthesis of new analogs and the study of their α-amylase inhibition activity. The sesquiterpene coumarin named coladonin (1) was quantitatively isolated from the chloroform extract of endemic roots. Subsequently, the oxidation of 1 the Jones oxidation reaction, used as a key reaction, afforded precursor 2. The condensation of oxidized coladonin (2) with various aryl aldehydes provided a series of new arylidene-based sesquiterpene coumarin derivatives (3a-m), which were characterized by NMR and ESI-HRMS experiments. All derivatives evaluated for their α-amylase inhibitory potential showed interesting α-amylase inhibition with IC values ranging from 7.24 to 28.98 μM. Notably, compounds 3k and 3m exhibited lower IC values (7.24 μM and 8.38 μM, respectively) compared to the standard (acarbose: IC = 9.83 μM). In addition, the structure-activity relationship (SAR) for all the compounds was studied. The most active compounds were found to be mixed-type inhibitors, which was revealed by kinetic studies. Furthermore, molecular docking studies were established for all synthesized analogs with the binding site for the α-amylase enzyme.