Vitamin E analyses in seeds reveal a dominant presence of tocotrienols over tocopherols in the Arecaceae family

Abstract

Tocopherols are thought to prevent oxidative damage during seed quiescence and dormancy in all angiosperms. However, several monocot species accumulate tocotrienols in seeds and their role remains elusive. Here, we aimed to unravel the distribution of tocopherols and tocotrienols in seeds of the Arecaceae family, to examine possible trends of vitamin E accumulation within different clades of the same family. We examined the tocopherol and tocotrienol content in seeds of 84 species. Furthermore, we evaluated the vitamin E composition of the seed coat, endosperm and embryo of seeds from 6 species, to determine possible tissue-specific functions of particular vitamin E forms. While seeds of 98.8% (83 out of 84) of the species accumulated tocotrienols, only 58.3% (49 out of 84) accumulated tocopherols. The presence of tocopherols did not follow a clear evolutionary trend, and appeared randomly in some clades only. In addition, the tissue-specific location of vitamin E in seeds revealed that the embryo contains mostly α-tocopherol (in seed tocopherol-accumulating species) or α-tocotrienol (in seed tocopherol-deficient species). However, some species such as Socratea exorrhiza mostly accumulate β-tocotrienol, and Parajubaea torallyi accumulates a mixture of tocopherols and tocotrienols in the embryo. This suggests that tocotrienols can play a similar protective role to that exerted by tocopherols in seeds, at least in some species of the Arecaceae family. We conclude that tocotrienol, rather than tocopherol, accumulation is a conserved trait in seeds of the Arecaceae family.