Occurrence of neoxanthin and lutein epoxide cycle in parasitic Cuscuta species

In the present study, xanthophyll composition of eight parasitic Cuscuta species under different light conditions was investigated. Neoxanthin was not detected in four of the eight species examined, while in others it occurred at the level of several percent of total xanthophylls. In C. gronovii and C. lupuliformis it was additionally found that the neoxanthin content was considerably stimulated by strong light. In dark-adapted plants, lutein epoxide level amounted to 10-22% of total xanthophylls in only three species, the highest being for C. lupuliformis, while in others it was below 3%, indicating that the lutein epoxide cycle is limited to only certain Cuscuta species. The obtained data also indicate that the presence of the lutein epoxide cycle and of neoxanthin is independent and variable among the Cuscuta species. The xanthophyll cycle carotenoids violaxanthin, antheraxanthin and zeaxanthin were identified in all the examined species and occurred at the level found in other higher plants. The xanthophyll and lutein epoxide cycle pigments showed typical response to high light stress. The obtained results also suggest that the ability of higher plants to synthesize lutein epoxide probably does not depend on the substrate specificity of zeaxanthin epoxidase but on the availability of lutein for the enzyme

Activity of tocopherol oxidase in Phaseolus coccineus seedlings

In the present study, we have demonstrated that membrane-free extracts of etiolated shoots of Phaseolus coccineus seedlings show tocopherol oxidase activity. For this reaction, presence of membrane lipids, such as lecithin and mixture of plant lipids was required. The rate of the reaction was the highest for α-tocopherol and decreased in the order α ≫ β > γ > δ tocopherols. In the case of α-tocopherol, the main oxidation product was α-tocopherolquinone, while for the other tocopherol homologues the dominant products were other derivatives. When the enzyme activity was measured in leaves, hypocotyls and roots of etiolated seedlings of P. coccineus, the oxidase activity was the highest in extracts of leaves and decreased towards the roots where no activity was detected. The effect of hydrogen peroxide and of different inhibitors on the reaction suggest that tocopherol oxidase does not belong to peroxidases or flavin oxidases but rather to multi-copper oxidases, such as polyphenol oxidases or laccases. On the other hand, catechol, the well-known substrate of polyphenol oxidases and laccases, was not oxidized by the enzyme, indicating a high substrate specificity of the tocopherol oxidase

Tocochromanols and fatty acid composition in flax (Linum usitatissimum L.) accessions

Flax, Linum usitatissimum, cultivars are grown throughout the world. Flax oil is a dietary source of polyunsaturated fatty acids, vitamin E, as well as phospholipids, sterols, and phenolic acids. Linseed plays a pivotal role in protecting cells from oxidative damage associated diseases, i.e., atherosclerosis, neurodegenerative disorders, cancer, and inflammation. In this study, two groups of L. usitatissimum seeds were used to evaluate and compare the content and composition of tocochromanols (vitamin E) and fatty acids. Group I included accessions originating from Poland and the Ukraine, while Group II encompassed worldwide flax cultivars (such as from the United States, Argentina, and Italy). A comparison of the tocochromanol profiles showed a higher content in Group I, although there were no significant differences in tocopherol content and composition between the genotypes within this group. All accessions in Groups I and II contained γ-tocotrienol and plastochromanol-8, which confirms the high nutritional value of flaxseeds. The composition of fatty acids varied depending on the varieties, with linolenic acid showing the greatest discrepancy. Based on the tocochromanol content and fatty acid composition, we conducted a principal component analysis (PCA) and cluster analysis, which revealed a greater similarity among the accessions in Group I. An analysis of the tocochromanol and fatty acid composition of flaxseeds is important from an agronomic and medicinal perspective and can be used to select the most appropriate flax cultivar

Antioxidant and neuroprotective activity of vitamin E homologues : in vitro study

Here we present comparative data on the inhibition of lipid peroxidation by a variety of tocochromanols in liposomes. We also show for the first time the potential neuroprotective role of all the vitamin E homologues investigated on the neuronally differentiated human neuroblastoma SH-SY5Y cell line. α-Tocopherol had nearly no effect in the inhibition of lipid peroxidation, while β-, γ-, and δ-tocopherols inhibited the reaction completely when it was initiated in a lipid phase. Similar effects were observed for tocotrienol homologues. Moreover, in this respect plastochromanol-8 was as effective as β-, γ-, and δ-tocochromanols. When the prenyllipids were investigated in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) test and incorporated into different lipid carriers, the radical oxidation was most pronounced in liposomes, followed by mixed micelles and the micellar system. When the reaction of tocochromanols was examined in niosomes, the oxidation was most pronounced for α-tocopherol and plastochromanol-8, followed by α-tocotrienol. Next, using retinoic acid-differentiated SH-SY5Y cells, we tested the protective effects of the compounds investigated on hydrogen peroxide (H(2)O(2))-induced cell damage. We showed that tocotrienols were more active than tocopherols in the oxidative stress model. Plastochromanol-8 had a strong inhibitory effect on H(2)O(2)-induced lactate dehydrogenase (LDH) release and H(2)O(2)-induced decrease in cell viability. The water-soluble α-tocopherol phosphate had neuroprotective effects at all the concentrations analyzed. The results clearly indicate that structural differences between vitamin E homologues reflect their different biological activity and indicate their potential application in pharmacological treatments for neurodegenerative diseases. In this respect, the application of optimal tocochromanol-carrying structures might be critical