Micromeria graeca L., essential Oils: In vitro and In silico evaluation

Abstract

The discovery of new natural molecules with therapeutic and/or cosmetic properties is a major concern of the pharmaceutical industry. In this sense, volatile compounds from plants have recently attracted significant interest as candidate natural substances. The aims of this research were to identify the volatile compounds of Micromeria graeca essential oil (MGEO) and to study its antimicrobial, antioxidant, and anti-enzymatic effects using in vitro and computational approaches, including molecular docking and molecular dynamics interaction studies. Gas chromatography coupled with mass spectrometry (GC-MS-MS) analysis revealed that MGEO contain 17 chemical compounds which were dominated by citral (29.3 %), neral (16.3 %), and caryophyllene oxide (10.4 %). The disc diffusion method and the broth microdilution techniques demonstrated that MGEO significantly inhibits the growth of Bacillus subtilis, Proteus mirabilis, Staphyloccocus aureus, and Candida albicans which the inhibition zone diameters ranged between 51 and 71 mm and MIC values ranged from 1.56 to superior to 50 mg/mL. The antioxidant effects indicate that MGEO exerts an important activity in 2,2′-diphenyl-1-picrylhydrazyl (DPPH), 2,2- azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric reducing antioxidant power (FRAP), cupric ion reducing activity (CUPRAC), ferrous chelating, and phosphomolybdenum models. Indeed, MGEO exerted significant antioxidant activity in several assays, demonstrating antioxidant powers with inhibitory values of 84.02 ± 3.25 mg TE/g of EO (Cuprac), 47.67 ± 0.22 mg TE/g of EO (ABTS), 45.45 ± 0.26 mg TE/g of EO (FRAP), 28.90 ± 1.19 mmol TE/g (Phosphomolybdenum), 22.41 ± 3.00 mg EDTAE/g of EO (Chelating), and 9.04 ± 0.67 mg TE/g of EO (DPPH). Remarkably, MGEO shows good potential to inhibit tyrosinase (41.05 mg KAE/g), butyrylcholinesterase and acetylcholinesterase (2.06 and 1.68 mg GALAE/g, respectively), and α-amylase (0.87 mmol ACAE/g) enzymes. Additionally, the molecular docking study demonstrated that each chemical interacted differently with the active regions of the five different enzymes. Collectively, our findings provides valuable information qualifying the studied plant as an interesting source of bioactive compounds.