Essential oils of Origanum compactum Benth: Chemical characterization, in vitro, in silico, antioxidant, and antibacterial activities

Abstract

This study was performed to investigate the phytochemical profile, and the, in vitro, and, in silico, antioxidant and antibacterial properties of the essential oil (EO) extracted from Origanum compactum. EO phytochemical screening was examined by gas chromatography coupled to mass spectrometry. The antioxidant potential, in vitro, was assessed using reducing power(FRAP), free 2,2 diphenylpicrylhydrazyl (DPPH) radical scavenging and total antioxidant capacity tests. Antibacterial properties against two Gram (-) and two Gram (+) bacteria were assessed using the minimal inhibitory concentration (MIC) and the disc diffusion methods. By use of molecular docking, antioxidant and antibacterial activities of oregano EO were also tested. Thymol (75.53%) was the major compound among the nine compounds identified in the EO of Origanum compactum, followed by carvacrol (18.26%). Oregano EO showed an important antioxidant capacity, as tested by FRAP and DPPH assays, with EC50 and IC50 values of 13.300 ± 0.200 and 0.690 ± 0.062 mg/mL, respectively. The same EO has a total antioxidant capacity of 173.900 ± 7.231 mg AAE/g EO. The antibacterial results showed significant activity of Origanum compactum EO against all tested bacteria, especially against S. aureus (MIC = 0.25 mg/mL) and B. subtilis (MIC = 0.06 mg/mL). In silico, carvacrol was the most active molecule against nicotinamide adenine dinucleotide phosphate oxidase (2CDU) and S. aureus nucleoside diphosphate kinase (3Q8U) with a glide score of -6.082, and -6.039 kcal/mol, respectively. Regarding the inhibition of E. coli beta-ketoacyl-[acyl carrier protein] synthase (1FJ4), piperitenone was the most active molecule with a glide score of -7.112 kcal/mol. In light of the results obtained, the EO of Origanum compactum Moroccan species can be used as promising natural food conservatives and an agent to fight antibiotic-resistant nosocomial microbes.