Formation of α-tocopherol hydroperoxide and α-tocopheroxyl radical: relevance for photooxidative stress in Arabidopsis

Abstract

Tocopherols, lipid-soluble antioxidants play a crucial role in the antioxidant defense system in higher plants. The antioxidant function of α-tocopherol has been widely studied; however, experimental data on the formation of its oxidation products is missing. In this study, we attempt to provide spectroscopic evidence on the detection of oxidation products of α-tocopherol formed by its interaction with singlet oxygen and lipid peroxyl radical. Singlet oxygen was formed using photosensitizer rose bengal and thylakoid membranes isolated from Arabidopsis thaliana. Singlet oxygen reacts with polyunsaturated fatty acid forming lipid hydroperoxide which is oxidized by ferric iron to lipid peroxyl radical. The addition of singlet oxygen to double bond carbon on the chromanol head of α-tocopherol forms α-tocopherol hydroperoxide detected using fluorescent probe swallow-tailed perylene derivative. The decomposition of α-tocopherol hydroperoxide forms α-tocopherol quinone. The hydrogen abstraction from α-tocopherol by lipid peroxyl radical forms α-tocopheroxyl radical detected by electron paramagnetic resonance. Quantification of lipid and protein hydroperoxide from the wild type and tocopherol deficient (vte1) mutant Arabidopsis leaves using a colorimetric ferrous oxidation-xylenol orange assay reveals that α-tocopherol prevents formation of both lipid and protein hydroperoxides at high light. Identification of oxidation products of α-tocopherol might contribute to a better understanding of the protective role of α-tocopherol in the prevention of oxidative damage in higher plants at high light.

Antioxidant and Signaling Role of Plastid-Derived Isoprenoid Quinones and Chromanols

“…•− and lipid radicals (such as L • , LO • and LOO • ), and also quenches and scavenges 1 O 2 [42,79]. This makes α-Toc important for membrane protection, where it inhibits lipid peroxidation, both radical and 1 O 2 -mediated [12,42,80].…”

Rapid Analysis of α-Tocopherol and Its Oxidation Products Using Supercritical Carbon Dioxide and Proton Transfer Reaction Ionization Mass Spectrometry

“…Therefore, the 46.5-s peak at m/z 447.383 is labeled as α-TQ in A peak observed at m/z 449.399 at 82.8 s listed in Table 2 bottom may correspond to αtocopherylhydroquinone. One of the two peaks observed for m/z 479.373 may be ascribed to the molecule (g), and one of the peaks observed at m/z 463.378 may correspond to 5-formyl-γ-tocopherol + OH, according to Tang et al 18) All the peaks appearing on the chromatogram at the same m/z are separated by a peak resolution (Rs) of at least 0.86, making it possible to select precursor ions for tandem MS. We are working to reduce the instrumental dispersion at the PTR flow tube, which is currently approximately two seconds. We aim to minimize the dispersion that gives a minimum peak width of less than one second so that all the peaks listed here are fully resolved at Rs > 1.5.…”

“…α-Tocopherol (α-T), in particular, is well known to prevent lipid peroxidation. [15][16][17] The α-T oxidation reaction scheme reported by Kumar et al 18) and Tang et al 19) is summarized in Figure 1 Although the details of the self-defense system of plant cells against 1 O2 using α-T are recently being determined by combining several analytical methods, the analytical process involves complex procedures and requires more than 30 min of chromatographic run time. Accordingly, a more rapid and sensitive method for investigating the defense system in individual cells is required.…”

Red to NIR-emissive anthracene-conjugated PMI dyes with dual functions: singlet-oxygen response and lipid-droplet imaging

“…a-Tocopherol is a well-known 1 O 2 scavenger formed by the triplet state of chlorophyll. 76,77 It reacts with 1 O 2 in solution and forms a diketone product named a-tocopherylquinone via intermediate radical species. After the addition of a-tocopherol in dye-MB solution, the emission spectra for each system were monitored after a long time upon visible light irradiation.…”