Tocopherol production in plant cell cultures

Abstract

Tocopherols, collectively known as vitamin E, are lipophilic antioxidants, essential dietary components for mammals and exclusively synthesized by photosynthetic organisms. Of the four forms (alpha, beta, gamma and delta), alpha-tocopherol is the major vitamin E form present in green plant tissues, and has the highest vitamin E activity. Synthetic alpha-tocopherol, being a racemic mixture of eight different stereoisomers, always results less effective than the natural form (R,R,R) alpha-tocopherol. This raises interest in obtaining this molecule from natural sources, such as plant cell cultures. Plant cell and tissue cultures are able to produce and accumulate valuable metabolites that can be used as food additives, nutraceuticals and pharmaceuticals. Sunflower cell cultures, growing under heterotrophic conditions, were exploited to establish a suitable in vitro production system of natural alpha-tocopherol. Optimization of culture conditions, precursor feeding and elicitor application were used to improve the tocopherol yields of these cultures. Furthermore, these cell cultures were useful to investigate the relationship between alpha-tocopherol biosynthesis and photomixotrophic culture conditions, revealing the possibility to enhance tocopherol production by favouring sunflower cell photosynthetic properties. The modulation of alpha-tocopherol levels in plant cell cultures can provide useful hints for a regulatory impact on tocopherol metabolism.

Tocopherol composition and antioxidant activity of Spanish wild vegetables

“…α-Tocopherol, which is the most active isoform of vitamin E (Caretto et al 2009), was the predominant isoform in all the leafy vegetables analysed. However, as it will be described below, in the four wild asparagus studied other forms were also codominant or even predominant.…”

“…Moreover, it has been considered the most active form in humans due to a preferential absorption and distribution of this compound in the human body (Caretto et al 2009). …”

Enhanced accumulation of phytosterols and phenolic compounds in cyclodextrin-elicited cell suspension culture of Daucus carota

“…When Geipel et al [52] characterized the production of α-tocopherol using photomixotrophic and heterorotrophic sunflower SCC, they found that the highest intracellular α-tocopherol levels (77 µg gDW -1 ) were obtained with a photomixotrophic cell culture grown in liquid MS supplemented with 0,5 mg L -1 naphthalene acetic acid, 0,5 mg L -1 benzylaminopurine, 15 g L -1 sucrose and maintained at 26 ºC and a light intensity of 125 µmol m -2 s -1 . Likewise, sunflower and tobacco SCC produced 24 µg gFW -1 and 41 µg gFW -1 of α-tocopherol when 150 µM homogentisic acid alone or in combination with 200 µM phytol was added, respectively [55,54]. Moreover, Caretto et al [55] analyzed the levels of α-tocopherol obtained from different sunflower sources and observed a production level of 11,4 µg gFW -1 (100 µg gDW -1 ), 7,3 µg gFW -1 (70 µg gDW -1 ), 18,1 µg gFW -1 (180 µg gDW -1 ), and 24 µg gFW -1 (239 µg gDW -1 ) in tissues of hypocotyls, stems, leaves and SCC, respectively.…”

“…Likewise, sunflower and tobacco SCC produced 24 µg gFW -1 and 41 µg gFW -1 of α-tocopherol when 150 µM homogentisic acid alone or in combination with 200 µM phytol was added, respectively [55,54]. Moreover, Caretto et al [55] analyzed the levels of α-tocopherol obtained from different sunflower sources and observed a production level of 11,4 µg gFW -1 (100 µg gDW -1 ), 7,3 µg gFW -1 (70 µg gDW -1 ), 18,1 µg gFW -1 (180 µg gDW -1 ), and 24 µg gFW -1 (239 µg gDW -1 ) in tissues of hypocotyls, stems, leaves and SCC, respectively.…”

Mediterranean non-cultivated vegetables as dietary sources of compounds with antioxidant and biological activity

“…Alfatocopherol, the chemical form with the highest vitamin E activity (Caretto, Nisi, Paradiso, & DeGara, 2009), was the most abundant one in all the studied samples (Table 3), except for Silybum marianum whose predominant form was δ-tocopherol As shown in Table 3, Cichorium intybus presented the highest total tocopherols content (2.98 mg/100 g), followed by Sonchus oleraceus (2.22 mg/100 g), while Scolymus hispanicus and Silybum marianum again stood out for their lowest contents (0.05 mg/100 g and 0.15 mg/100 g, respectively), which may be related to the fact that these samples are peeled leaves, only containing midrib tissues.…”