Taxonomy of Vitamin E Distribution Across the Plant Kingdom

Investigating the relationship between vitamin E composition in seed, leaf and root tissue and phylogeny by comparison of species representing diverse families across the Plant Kingdom.

Seeds and seedlings of Magnolia sieboldii, native to eastern Asia, are being analysed for tocochromanols.

Tocochromanols are a group of fat-soluble compounds that are synthesised only by photosynthetic organisms. Tocochromanols are collectively known as the vitamin E family, and are essential in the human diet. There are eight naturally occurring isomers of tocochromanols (alpha-, beta-, gamma- and delta-tocopherol, and alpha-, beta-, gamma- and delta-tocotrienol), all of which have high antioxidant activities and protect membrane lipids from oxidation. Tocopherols appear to occur ubiquitously in all higher plants, with alpha-tocopherol generally cited as the most abundant tocochromanol in photosynthetic tissue, whilst gamma-tocopherol is often reported to be the predominant isoform in seeds. Due to the natural abundance of alpha-tocopherol and its high antioxidant activity it has been subject to the most intense research interest, especially with regard to human nutrition and disease prevention. More recently, tocotrienols have received greater attention, since new evidence suggests that they may be more effective in the prevention or treatment of certain cancers. Tocotrienols are reported to be less widespread than tocopherols, occurring only in some plant families, where they are found mainly in seeds and specialised cells of latex tubers. However, many plant families have yet to be analysed. Evaluation of tocochromanol composition of diverse plant species could lead to identification of wild species with high levels of tocochromanols, which may have potential as nutritionally-rich crop species for sustainable agriculture. In addition, characterisation of tocochromanols in species ranging from the most evolutionarily ancient to the most recent could provide an insight into the evolution of the tocochromanol biosynthesis pathway in higher plants.

A study was started in 2010 under way using the unique material in the MSB Partnership to investigate the existence of a systematic pattern of tocochromanol distribution across the plant kingdom, and also to determine the tissue-specific tocochromanol composition by analysing seeds, leaves, roots, stems and cotyledons of a range of plant species. This project is part of the ‘Seed Futures’ research theme.

Several undergraduate and postgraduate students have been trained in the framework of this project, with support from the Nuffield Foundation in the form of an Undergraduate Research Bursary. The outputs of this project are being published in peer-reviewed journals.