Antioxidant effect of oregano (Lippia berlandieri v. Shauer) essential oil and mother liquors

The conventional steam distillation process for oregano (Lippia berlandieri v. Shauer) essential oil extraction produces large volumes of mother liquor. This residual liquid represents a potential value because the soluble antioxidants it contains. Essential oil and ethyl acetate mother liquor extracts (MLEs) were evaluated for antioxidant activity. Total phenolic content and antioxidant activities by the 2-2′-diphenyl-1-picrylhydrazyl (DPPH) method, by the deoxyribose degradation assay, and by oxidation of low density lipoproteins (LDL) with CuSO₄ were evaluated. Oil yield was 4.34%. Total phenolic content was 151 ± 2.00 and 150.5 ± 0.98 mg of GAE (gallic acid equivalents)/mL for the essential oil and MLEs, respectively. DPPH assay showed a low radical scavenging activity (RSA) for oregano essential oil. Meanwhile MLEs exhibited no significant RSA at low concentrations, but at higher concentrations (100 μg/mL), it was superior to those exhibited by the controls ascorbic acid and butylated hydroxytoluene (BHT). Deoxy-d-ribose assay results for both essential oil and MLEs showed a good hydroxyl radical RSA at the concentrations tested. Essential oil and MLEs delayed induction time effectively. Solubility problems, chemical constituents, and their hydrophilic–lipophilic distribution are key factors that explain samples behavior for an eventual use of these natural products.