Differences in the Compositions of Vitamin E Tocochromanol (Tocopherol and Tocotrienol) in Rice Bran Oils Produced in Japan and Other Countries.

In this study, we investigated the compositions of vitamin E tocochromanol [tocopherol (Toc) and tocotrienol (T3)] in crude and refined rice bran oil (RBO) produced in Japan and other countries, including Brazil, Thailand, and Vietnam, based on high-performance liquid chromatography analysis. All RBO analyzed contained α-, β- and γ-Toc and α-, γ- and δ-T3. Japanese crude RBO, although not refined RBO, also contained β-T3. Furthermore, total Toc contents in both Japanese crude and refined oils were found to be higher than those in the crude and refined RBO from other countries. Total T3 contents in Japanese crude RBO were similar to those in the crude RBO from Brazil and Vietnam. The α-Toc and α-T3 contents in Japanese crude and refined RBO were considerably higher than those in the crude and refined RBO produced in other countries, whereas in contrast, γ-Toc and γ-T3 contents in Japanese crude and refined RBO were lower. Consequently, the ratios of total α-Toc and α-T3 contents to total γ-Toc and γ-T3 contents in Japanese crude and refined RBO (1.75 and 1.91, respectively) were notably higher than those in the crude and refined RBO produced in other countries. Similarly, the ratios of total Toc to total T3 in Japanese crude and refined RBO were higher than those in the crude and refined RBO produced in other countries. These results accordingly indicate that the ratio of total α-Toc and α-T3 contents to γ-Toc and γ-T3 contents could be used as an effective index to discriminate between the RBO produced in Japan and that produced in other countries.

Vietnam. Refined RBO produced in Japan and other countries was purchased at a local market or obtained via internet shopping.

Fatty acid composition and Toc and T3 content
For the purposes of measuring the fatty acid composition and Toc and T3 contents of RBO, we respectively used gas liquid chromatographic method 2.4.2.3-2013 6 and highperformance liquid chromatographic method 2.4.10-2013 7 , as described in the Standard Methods for the Analysis of Fats, Oils and Related Materials published by The Japan Oil Chemists Society 2013 .
Experiments were performed in triplicate and all data are presented as averages and standard deviations. Data were statistically analyzed using an analysis of variance ANOVA , and the Tukey-Kramer test was used to determine differences among samples.

Results and Discussion
In total, we determined the fatty acids composition of 268 foreign and 86 Japanese crude RBO samples and 25 foreign and 30 Japanese refined RBO samples. Table 1 shows details of the fatty acid composition of RBO produced in Japan, Brazil, India, Thailand, and Vietnam. All crude and refined RBO were found to have similar fatty acid profiles, with oleic 18:1 and linoleic 18:2 acids, the percentages compositions of which were 40 -45 and 31 -35 , respectively, being major components. In both the crude and refined RBO produced in Japan, the proportion of palmitic acid 16:0 was slightly lower than that in the RBO produced in other countries, whereas the proportion of oleic acid was slightly higher in Japanese crude RBO compared with that in the crude RBO produced in Brazil and Thailand.
We determined the Toc and T3 contents of 88 foreign and 51 Japanese crude RBO samples randomly selected from among those for which the fatty acid compositions had been measured, the details of which are shown in Table 2. All crude RBO samples were found to contain α-, β-, and γ-tocopherols α-Toc, β-Toc, and γ-Toc and α-, γ-, and δ-tocotrienols α-T3, γ-T3, and δ-T3 . In contrast to the crude RBO produced in other countries, Japanese crude RBO also contained β-tocotrienol β-T3 , In general, Japanese crude RBO contained higher amounts 60 mg/100 g of Toc than the crude RBO produced in other countries 16-34 mg/100 g . The contents of total T3 in Japanese crude RBO were similar to those detected in Brazilian and Vietnamese crude RBO, whereas those in the crude RBO produced in Thailand were somewhat lower. Among all crude RBO samples analyzed, those produced in Japan were found to have the highest total Toc and T3 contents. Furthermore, we detected significant differences between the crude RBO produced in Japan and other countries with respect to the ratio of total Toc to total T3, with that for Japanese crude RBO 0.80 being higher than that for the crude RBO produced in other countries 0.30-0.44 . Similarly, we found that the ratio of total α-Toc and α-T3 to total γ-Toc and γ-T3 for Japanese crude RBO 1.75 was considerably higher than that for the crude RBO produced in other countries 0.18-0.24 . These results accordingly revealed that although the fatty acid composition of crude RBO produced in other countries is similar to that of Japanese crude RBO, the compositions of Toc and T3 in Japanese crude RBO differ from those in the RBO produced in other countries, and indeed we detected no significant relationship between the fatty acid and Toc and T3 compositions of crude RBO.
We also determined Toc and T3 contents in 28 foreign and 30 Japanese commercial refined RBO, the compositions which are shown in Table 3. All refined RBO were found to contain α-Toc, β-Toc, and γ-Toc and α-T3, γ-T3 and δ-T3, although we detected no β-T3 in Japanese refined RBO. Regardless of the country of origin, the contents of Toc and T3 in all refined oils were found to be lower than those in crude oils, thereby indicating that the levels of these constituents are reduced during the refining process. Nevertheless, we established that Japanese refined RBO contains higher amounts 41 mg/100 g of Toc than that produced in other countries 16-25 mg/100 g . In this regard, we suspect that the high temperatures to which RBO is exposed during the refining process, particu-larly the deodorization step, could contribute to the decomposition of Toc and T3. The total T3 content in Japanese refined RBO was also found to be slightly higher than that in the refined RBO produced in India and Thailand. We also detected significant differences between the refined RBO produced in Japan and other countries with respect to the ratio of total Toc to total T3, with that in Japanese refined RBO 0.84 being notably higher than that in the refined RBO produced in other countries 0.42-0.58 . Similarly, the ratio of total α-Toc and α-T3 to total γ-Toc and γ-T3 in Japanese refined oil 1.91 was found to be considerably higher than that in the refined RBO produced in other countries 0.24-0.31 . These results thus revealed that Toc and T3 compositions in Japanese refined RBO differ from those in RBO produced in other countries, particularly with respect to the ratio of total α-homologs to total γhomologs. Moreover, we established that the ratio of total α-homologs to total γ-homologs is essentially unaffected by the refining process. These finding accordingly indicate that the ratio of total α-homologs to total γ-homologs could be used as an effective index to discriminate between the RBO produced in Japan and that produced in other countries.
It is reasonable to assume that differences detected in the Toc and T3 compositions of Japanese and foreign RBO reflect differences in the rice varieties cultivated in different countries, with the RBO produced in Japan being primarily derived from japonica rice, whereas that produced in Brazil, Thailand, and Vietnam is based on indica rice. Indeed, Huang and Ng 8 found that in Taiwan, the α-Toc content in japonica rice is considerably higher than that in indica rice. A similar observation has also been reported by Sekine et al. 9 , who suggested that the higher α-Toc content detected in japonica rice is attributable to the higher activity of γ-Toc transmethylase, which catalyzes the conversion from γ-Toc. Given our findings indicating notably higher Toc and T3 contents in Japanese RBO, as well as the higher ratios of α-homologs to γ-homologs, we believe that the Toc and T3 compositions of RBO could provide the basis for a useful method for discriminating among RBO produced in Japan and other countries.

Conclusions
Our analyses of the Toc and T3 compositions of crude and refined RBO revealed significant differences between contents in the RBO produced in Japan and other countries. The total Toc content in Japanese RBO was found to be notably higher than that in the RBO produced in other countries. Moreover, compared with that produced in other countries, the RBO produced in Japan was found to be characterized by a significantly higher ratio of α-homologs to γ-homologs. These differences are assumed to be associated with the different varieties of rice cultivated in the respective countries.