Food contains various nutraceutical compounds that have been shown to exert a wide range of biological activities. These dietary components include vitamins, phytochemicals, fatty acids, polyphenols, and others. Their bioactivity has been significantly associated with antioxidant properties, which provide protection against oxidative damage connected with many diseases. Among the nutraceutical compounds, vitamin E complex exhibits the highest antioxidant activity. This group include α, β, γ and δ-tocopherols, analogous tocotrienols and plastochromanol-8, also named as tocochromanols. Because of their antioxidant function, tocochromanols play a major role in protecting membrane lipids from oxidation. Therefore, they are abundantly found in plant-derived food products, but seed oils are considered to be the best source of these compounds for nutrition. Their content and composition varies between species. Additionally, as a result of their structural differences, vitamin E homologues possess different biological activity, including antioxidant action.In the present study, a comparative analysis of the antioxidant potential measured as the inhibition of lipid peroxidation by a variety of vitamin E homologues has been performed. As model systems, we have used liposomes prepared from a mixture of natural chloroplast lipids. To initiate lipid peroxidation outside and inside lipid membranes, we have used both hydrophobic (AMVN), and hydrophilic (AIPH) azo-initiator. The antioxidant potential during lipid peroxidation was measured as the inhibition of lipid peroxides formation and simultaneous tocochromanol content decay using the HPLC technique.
The obtained results showed that vitamin E homologues effectively inhibited the lipid peroxidation generated in liposome membranes. When lipid peroxidation was generated in the lipid phase, the highest efficiency of inhibition was observed for δ-Toc, δ-Tt and PC-8 whereas α-Toc and α-Tt showed the least inhibitory effect. During the progress of peroxidation, a decrease in the content of tocochromanols was also observed. In the case of oxidative stress generated outside the membrane, efficiency in inhibition of lipid peroxidation was similar for all the compounds examined, except of α-homologues which showed the lowest efficiency.Summarizing, vitamin E homologues have showed different antioxidant effect in the liposome membrane model. Their action differs between homologues and depends on the type of lipid peroxidation initiator used. Our results indicate that the total antioxidant potential of different plant-derived products (i.e. plant oils) highly depends on the
qualitative composition of antioxidants, including one of the most active lipid-soluble members of vitamin E complex.
Audience Take Away:
• Vitamin E homologues effectively inhibit the lipid peroxidation generated in liposome membranes
• Their action differs between homologues and depends on the type of lipid peroxidation initiator used
• The total antioxidant potential of different plant-derived products highly depends on the qualitative composition of antioxidants, including members of vitamin E complex