Lipid Peroxidation (LPO) Assay
Lipid peroxidation is a well-known example of oxidative damage in cell membranes, lipoproteins, and other lipid-containing structures. Peroxidative modification of unsaturated phospholipids, glycolipids, and cholesterol can occur in reactions triggered by i) free radical species such as oxyl radicals, peroxyl radicals, and hydroxyl radicals derived from iron-mediated reduction of hydrogen peroxide or ii) non-radical species such as singlet oxygen, ozone, and peroxynitrite generated by the reaction of superoxide with nitric oxide.
Malondialdehyde (MDA) and 4-hydroxyalkenals are important toxic byproducts of lipid peroxidation. The measurement of the amounts of such aldehydes has been widely used as an index of lipid peroxidation in vitro and in vivo.
4-Hydroxynonenal (4-HNE) is produced as a major product of the peroxidative decomposition of ω-6 polyunsaturated fatty acids (PUFA) and possesses cytotoxic, hepatotoxic, mutagenic, and genotoxic properties. Increased levels of HNE were found in plasma and various organs under oxidative stress conditions.
MDA is in many instances the most abundant individual aldehyde resulting from lipid peroxidation. In vitro MDA can alter proteins, DNA, RNA, and many other biomolecules.
G-Biosciences’ LPO assay kit measures MDA and HNE concentrations as an index of lipid peroxidation. Reactions between indoles and aldehydes (MDA and HNE) are initiated by acid-catalyzed attack at the 3-position of the indole ring to give a diindolylalkane (chromophore) with maximum absorbance in the region of 580-620 nm.
In our assay an indol (Reagent A) reacts quickly with MDA and HNE in acidic medium, yielding a chromophore (C) with a high molar extinction coefficient at its maximal absorption wavelength of 586 nm.
Reagent A + MDA → C (λmax = 586 nm)
Reagent A + HNE → C (λmax = 586 nm)