Thymus vulgaris extract: A green approach to antioxidant efficacy, antibacterial action, and corrosion inhibition

Abstract

This study evaluates the multifunctional properties of phenolic fractions from Thymus vulgaris , focusing on antioxidant, antibacterial, and corrosion inhibition activities. Extracts were prepared using organic solvents, and the total polyphenol and flavonoid contents were quantified by the Folin-Ciocalteu and FeCl 3 spectrophotometric methods, respectively. Antioxidant capacity was assessed using the FRAP assay, β-carotene-linoleate bleaching test, and an enzymatic method. Antibacterial activity was tested via the disc diffusion method, and corrosion inhibition was analyzed using electrochemical impedance spectroscopy (EIS) and Tafel polarization techniques on X48 carbon steel in 1 M HCl. The methanolic extract (MetE) displayed the highest polyphenol (270.90 ± 1.19 µg GAE/mg) and flavonoid (21.92 ± 1.14 µg QE/mg) contents, with superior antioxidant activity, achieving 92.52% inhibition in the β-carotene-linoleate test, 3941.35 ± 137.08 µg/mL in the FRAP assay, and IC 50 = 0.296 ± 0.038 mg/mL for XO inhibition. Antibacterial assays revealed significant activity against Gram-positive and Gram-negative bacteria, while MetE achieved 94.97% corrosion inhibition efficiency at 12.5 mg/mL. These findings highlight T. vulgaris as a rich source of bioactive compounds with applications in health, pharmaceuticals, and industry. This study demonstrates the potential of T. vulgaris as a sustainable, eco-friendly alternative for combating oxidative stress, bacterial infections, and corrosion. • Thymus vulgaris extracts demonstrate significant antioxidant, antibacterial, and anti-corrosion activities. • Superior antioxidant activity of MetE is attributed to its high phenolic and flavonoid content. • Bioactivity of the extracts correlates with phenolic concentration: MetE > EAE > ChE > BolE. • MetE exhibited the highest multifunctional efficacy with 94.97% inhibition, outperforming EAE (94.58%), ChE (92.23%), and BolE (90.55%). • MetE is identified as a potent, eco-friendly corrosion inhibitor for X48 steel in acidic media.