Origanum vulgare Ethanol Extract Modulates the Activity of Antioxidant Enzymes

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Plant-based preparations with antioxidant and antimicrobial influences can be effectively applied for both the prevention and adjuvant therapy of various diseases. The presented study investigates the antioxidant and pro-oxidant properties of ethanol extract from Origanum vulgare (OVEE) collected in Armenia, focusing on its radical scavenging activity, phenolic and flavonoid content, lipid peroxidation inhibition, nitric oxide (NO) modulation, antioxidant enzyme activity, and gene expression in Escherichia coli NM111 cells. The DPPH assay revealed significant radical scavenging activity (IC50 = 19.97 ± 0.51 μg/mL), in case of catechin (IC50 = 13.08 ± 0.04 μg/mL). OVEE exhibited a high total phenolic (555.08 ± 5.60 μg GAE/mg) and flavonoid contents (31.39 ± 1.16 μg QE/mg), correlating with its antioxidant activity. Lipid peroxidation, assessed via TBARS assay, was significantly inhibited by OVEE (20.72 ± 2.47%) (in case of the positive control -(α-tocopherol) 91.1 ± 1.9%). Unexpectedly, OVEE increased NO levels in E. coli cells, suggesting potential pro-oxidant activity influenced by phenolic compound structure, pH, and metal ion interactions. Enzymatic antioxidant defense was enhanced, with SOD and catalase activities increasing by approximately 40 and 35%, respectively, under the OVEE treatment. Additionally, OVEE induced the expression of the katG::lacZ gene fusion by 1.41-fold, p < 0.001, with further induction observed under oxidative stress. These findings highlight dual antioxidant-prooxidant nature of OVEE, emphasizing its potential antibacterial mechanisms and broader biological significance for therapeutic applications.