Chemical composition, biological activities, and anti-corrosion performance of Moroccan essential oil Thymus vulgaris from the Oued Amlil region, Taza

Abstract

The study investigated the antibacterial, antioxidant, antidiabetic, ADMET (absorption-distribution-metabolism-excretion-toxicity) properties, and anticorrosion of essential oil extracted from Thymus vulgaris collected in the Oued Amlil region of Taza. The phytochemical profile of the Thymus vulgaris essential oil via gas chromatography-mass spectrometry (GC-MS) technique identified non-oxygenated monoterpenes (19.07 %), oxygenated monoterpenes (77.61 %), non-oxygenated sesquiterpenes (1.44 %), and oxygenated sesquiterpenes (1.88 %). The main constituents were carvacrol (59.70 %), thymol (16.5 %), and γ-terpinene (11.11 %). The in vitro microdilution antibacterial effect test showed significant activity against all tested bacteria, except for some Gram-negative bacteria (Pseudomonas, Pantoae spp.), which showed resistance. Thymus vulgaris oil also showed antioxidant activity, with IC₅₀ values of 5.94±0.22 µg/mL using 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay and 3.03±0.17 (µg/mL) using 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) assay. The tested oil revealed good inhibitory activity on α-amylase and α-glucosidase with IC₅₀ values of 0.92±0.02 mg/mL and 0.19±0.01 mg/mL, respectively. The ADME study of the identified phytoconstituents of Thymus vulgaris essential oil confirms their important pharmacokinetic and drug-like properties. Additionally, the inhibitory effect of Thymus vulgaris essential oil on carbon steel corrosion was evaluated using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. The surface morphology of the uninhibited and inhibited carbon steel coupons was analyzed using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). Electrochemical studies showed that Thymus vulgaris oil acts as a good mixed corrosion inhibitor for carbon steel substrate in one molar of hydrochloric acid (1 M HCl) since an inhibition efficiency of 94.4 % was reached with 400 ppm at 303 K.