Chemical variability, pharmacological potential, multivariate and molecular docking analyses of essential oils obtained from four medicinal plants

Essential oils (EOs) hold tremendous medicinal attributes and are greatly exploited industrially worldwide. In the present study, the chemical composition of five EOs prepared from four aromatic plants were revealed together with their inhibitory activities against five key clinical enzymes (alpha-amylase, alpha-glucosidase, tyrosinase, acetyl- and butyryl-cholinesterase). Limonene (84.3%) and sabinene (38.1%) were the most dominant constituents present in Citrus aurantium fruit peel and leaf EOs respectively. Turmerone (31.4%), ar-turmerone (16.1%), and turmerol (14.6%) were the principal components identified in Curcuma longa rhizome EO. Additionally, Morinda citrifolia fruit EO was abundant in octanoic acid (78.9%), while carvacrol (17.9%), delta-3-carene (15.2%), and camphor (12.9%) were predominant in Plectranthus amboinicus EO. The investigated EOs were all active inhibitors of acetylcholinesterase, amylase, and tyrosinase. Morinda citrifolia and P. amboinicus EOs inhibited butyrylcholinesterase exclusively, while M. citrifolia and C. aurantium fruit peel EOs displayed inhibition against glucosidase as well. Due to strong interactions with their active sites, molecular docking showed turmerone followed by carvacrol to have the highest binding affinities with target enzymes. Moderate to strong antioxidant potential was also demonstrated by all EOs. However, P. amboinicus EO presented the most potent antioxidant capacity and contained the highest amount of phenolics, while M. citrifolia EO was the weakest among all. Besides, a strong positive correlation was noted between EOs' antioxidant capacities and total phenolic content. With the exception of C. aurantium leaf and C. longa EOs which showed similar bio-activities and were grouped together, the other EOs were subdivided into distinct groups by principal component analysis. Altogether, this study highlighted interesting pharmacological properties of the investigated EOs that could serve as sources of bioactive ingredients with potential industrial applications.