2.9. Measurement of MDA for Lipid Peroxidation

Malondialdehyde (MDA), an end product of the lipid peroxidation, was used as an oxidative stress marker, and its concentration was measured using a thiobarbituric acid reactive substance (TBARS) assay kit obtained from the Cayman Chemical Company. The HepG-2 cells were treated with AAP in the presence and absence of sage essential oils, the supernatant of cells lysate or the standard sodium dodecyl sulfate, and the color reagent was added, heated to 100 °C for 1 h, and immediately cooled in an ice bath and centrifuged. The absorbance of the product was measured at a wavelength of 540 nm on a microplate reader, SpectraMax M II (Molecular Devices, LLC. San Jose, CA, USA). The extent of lipid peroxidation was quantified by estimating the MDA concentration. The results are expressed as micromoles of MDA equivalents formed per liter.