Antioxidant activity of vitamin E homologues in model systems
Abstract The effect of tocopherols, tocotrienols and plastochromanol-8 in the inhibition of lipid peroxidation of liposomes prepared from natural chloroplast lipids, initiated by both water-soluble and lipid soluble azo-compounds, has been studied. In the case of tocopherols, α-tocopherol showed nearly no effect in the inhibition of lipid peroxidation, while β-, γ- and δ-tocopherols inhibited the reaction completely when it was initiated by lipid-soluble AMVN. Similar effects were observed for tocotrienol homologues. In the investigated reaction plastochromanol-8 was as effective as β-, γ- and δ-tocochromanols. When peroxidation was initiated by water-soluble AIPH in liposomes, the order and extent of inhibition was similar to those of AMVN initiator. However, in this case, α-tocopherol and α-tocotrienol showed more pronounced inhibition. When the prenyllipids were investigated in DPPH test, when incorporated into soy lipid liposomes, mixed micelles and micelles, DPPH oxidation was most pronounced in liposomes, followed by mixed micelles and micellar system. When the reaction of α-tocopherol, α-tocotrienol, plastochromanol-8 and α-tocopherol phosphate was examined in niosomes, the oxidation was most pronounced for α-tocopherol and plastochromanol-8, followed by α-tocotrienol. α-tocopherol phosphate showed no activity in this respect. The obtained results were discussed in light of the prenyllipid structures and their localization in the investigated lipid systems.