Abstract: Vitamin E, including of tocotrienols and tocopherols, is one of miner nutrients that must be acquired regularly from dietary sources. The structure of tocotrienols differs from that of tocopherols by the presence of three trans-double bonds in the hydrocarbon chain. In this study, a reverse-phase HPLC method was used to simultaneously measure the contents of either tocopherols or tocotrienols in the brown rice, and their contents were compared among 18 indica and 16 japonica cultivars. The results showed that the contents of these vitamin E isomers were extremely different between indica and japonica rice, and the mean content of total tocopherol or vitamin E was significantly higher (P<0.01) in japonica rice than in indica rice, while the total tocotrienol content showed no differences between them. The principal isomer of vitamin E was also different between the two subspecies, for example, γ-tocotrienol was the predominant compound in indica rice, on the contrary, in japonica rice, the most abundant isomer was α-tocopherol. 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 α-tocopherol content was positively correlated with α-tocotrienol content in rice. The same relationship was also presented between the contents of γ-tocopherol and γ-tocotrienol, but there was a negative correlation between contents of α- and γ-isomers. Taking together, all the present results provide some useful information for research on vitamin E metabolism or nutritional improvement in rice.

Key words: Oryza sativa L., Vitamin E, Tocopherol, Tocotrienol, HPLC