Variation and Distribution of Vitamin E and Composition in Seeds Among Different Rice Varieties

Vitamin E is an essential nutrient that must be acquired regularly from dietary sources. It is a group of compounds consisting of tocotrienols and tocopherols. The structure of tocotrienols differs from that of tocopherols by the presence of 3 trans-double bonds in the hydrocarbon chain. In this study, a reverse-phase (RP) HPLC method was used to simultaneously measure the contents of either tocopherols or tocotrienols in brown rice, and to compare these parameters among 18 indica and 16 japonica rice (Oryza sativa L.) varieties. The results showed that the proportion of these vitamin E isomers differed substantially between indica and japonica rice varieties. The mean contents of vitamin E and total tocopherol were significantly higher (P < 0.01) in japonica rice than in indica rice, while the total tocotrienol content showed no difference between indica and japonica rice. The principal isomer composition of vitamin E was also different between the 2 subspecies. For example, γ-tocotrienol was the predominant component in indica rice, while the most abundant isomer was α-tocopherol in japonica rice. The ratio of total tocotrienols to tocopherols was also significantly higher (P < 0.01) in indica (1.61) than in japonica rice (0.95). Pearson's correlation analysis demonstrated that the content of α-tocopherol was positively correlated to that of α-tocotrienol in rice. The same relationship was observed for γ-tocopherol and γ-tocotrienol, but there was a negative correlation between α- and γ-isomers. Taken together, the results provide valuable information for studying the vitamin E metabolism or nutritional improvement in rice.

摘要维生素E是人与动物必须从食物中摄取的微量营养元素之一, 根据侧链的饱和度可将其分为生育酚和三烯生育酚, 水稻种子中均含二者。本研究利用反相高效液相色谱法测定了18份籼稻和16份粳稻品种糙米中维生素E各异构体的含量。结果表明, 种子中各异构体的含量在籼稻与粳稻间存在显著差异, 粳稻种子中的生育酚和维生素E含量高于籼稻; 籼稻种子中三烯生育酚与生育酚的比值(1.61)极显著高于粳稻(0.95), 籼稻中以γ-三烯生育酚为主, 而粳稻中主要含α-生育酚。水稻种子中同种类型异构体(即α-型间或γ-型间)含量间具有显著正相关, 但γ-型与α-型异构体间呈显著负相关。这些数据为进一步研究水稻种子中维生素E的代谢调控和营养品质改良提供了有益的表型数据。