Regional distribution of tocopherols and fatty acids within soybean seeds

Seed coat, axis, and sections of cotyledons in three soybean cultivars were analyzed by high-performance liquid chromatography for tocopherols, and by gas-liquid chromatography for acyl lipids. Tocopherols were predominantly detected in axis, followed by cotyledons and seed coat. With a few exceptions, dominant components were γ- and δ-tocopherols, with much smaller amounts of α- and β-tocopherols. However, α-tocopherol was higher (P<0.05) for the Mikawajima cultivar than for Okuhara and Tsurunoko in all tissues. Triacylglycerols (TAG) were the major fraction of total lipids, representing 70% in axis and coat and 94% in cotyledons. A small difference (P<0.05) occurred in fatty acid composition of TAG when comparing seed coat to the axis. The fatty acid composition of phosphatidylinositol (PI) differed (P<0.05) from phosphatidylethanolamine (PE) and phosphatidylcholine (PC) in each tissue. Principally, the percentage of palmitic acid was higher, especially in axis and coat. In PE and PC, linoleic was greater, followed by palmitic, in all samples except for seed coat tissue in Mikawajima. The percentages of palmitic acid in both phospholipids were significant higher in the seed coat tissue from this cultivar than in cotyledon or axis of the other varieties. These results suggest that the differences in soybean cultivars could be appreciable, based on the distribution of tocopherols and fatty acids in each component part within soybean seeds.