Chemical Composition, Anti--Glucosidase Activity, and Molecular Modelling Studies of Cleistocalyx operculatus Essential Oil

In this study, chemical components, alpha-glucosidase inhibitory activities, and molecular modelling studies of the essential oil extracted from the Cleistocalyx operculatus leaves were investigated. In total, thirty compounds were identified using GC/MS, representing 98.3% of the oil. Of these, the two most dominant constituents of the essential oil were determined as (Z)-beta-ocimene (30.4%) and allo-ocimene (31.6%). The alpha-glucosidase inhibitory experiments indicated that the essential oil exhibited potent alpha-glucosidase inhibitory activities, with IC50 values of 61.82 +/- 3.91 mu g/mL. For further investigation into inhibitory mechanisms, molecular docking simulations were performed to investigate structural interactions between two dominant constituents and the alpha-glucosidase protein. The simulation revealed that allo-ocimene (31.6%) and (Z)-beta-ocimene (30.4%) have protein binding affinities of -5.358 and -5.330 kcal/mol, respectively. Moreover, molecular dynamic simulation indicated that the complexes of two compounds and the target protein were stable over 100 ns. Overall, these findings suggest that the essential oil of C. operculatus leaves could be a natural source of potential alpha-glucosidase inhibitors.