Biological Redox Impact of Tocopherol Isomers Is Mediated by Fast Cytosolic Calcium Increases in Living Caco-2 Cells

Most of the biological impacts of Vitamin E, including the redox effects, have been raised from studies with α-tocopherol only, despite the fact that tocopherol-containing foods carry mixed tocopherol isomers. Here, we investigated the cellular mechanisms involved in the immediate antioxidant responses evoked by α-, γ- and δ-tocopherol in Caco-2 cells. In order to track the cytosolic redox impact, we performed imaging on cells expressing HyPer, a fluorescent redox biosensor, while cytosolic calcium fluctuations were monitored by means of Fura-2 dye and imaging. With this approach, we could observe fast cellular responses evoked by the addition of α-, γ- and δ-tocopherol at concentrations as low as 2.5 μM. Each isomer induced rapid and consistent increases in cytosolic calcium with fast kinetics, which were affected by chelation of extracellular Ca2+, suggesting that tocopherols promoted a calcium entry upon the contact with the plasma membrane. In terms of redox effects, δ-tocopherol was the only isomer that evoked a significant change in the HyPer signal at 5 μM. By mimicking Ca2+ entry with ionomycin and monensin, a decline in the HyPer signal was induced as well. Finally, by silencing calcium with 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA), an intracellular Ca2+ chelator, none of the isomers were able to induce redox changes. Altogether, our data indicate that an elevation in cytoplasmic Ca2+ is necessary for the development of a tocopherol-induced antioxidant impact on the cytoplasm of Caco-2 cells reported by HyPer biosensor.

Isomer composition of tocopherols in seabuckthorn (Hippophae rhamnoides L.) seeds in forest-steppe area of Altai territory

Estimation of tocopherol isomers composition in seed oil of seabuckthorn (H. rhamnoides ssp. mongolica) varieties is represented. It has been established that α-tocopherol is the dominant tocopherol in the lipids of the seabuckthorn seeds, the mean content of which for two years has been ranged from 2.1 (Dar Katuni) to 4.8 mg/100 g (Yantarnaya). In general within the evaluated group of subspecies, the mean content of α- tocopherol was determined at 3.5±0.3 mg/100 g. β-, γ- and δ-tocopherols were characterized by low content, accumulating an average for two years at 0.5±0.1, 1.3±0.1 and 0.7±0.3 mg/100 g, respectively.

Sour cherry seed as an industrial gamma tocopherol source

In our experiments sour cherry kernels were investigated. The kernels of different sour cherry cultivars were originated from Újfehértói Gyümölcstermesztési Kutató és Szaktanácsadó Nonprofit Közhasznú Kft. Tocopherol profile, oil yields and nutritional value were stood in focus of examinations. We started processes preparing of sour cherry kernels. After the preparation recovered non-polar fraction was investigated. We worked with formerly developed chromathographic system, which is capable to separate different tocopherol isomers efficiently. We measured concentration of each tocopherol isomers and registered those and their relation in different oil samples. According to received data, alpha-, gamma- and delta-tocopherol appeared in samples, but beta-tocopherol could not be detected. It became clear that level of gamma-tocopherol is far higher than alfa- or gamma-isomer, it is concentration exceeded 1–1.5 mg ml-1.