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Tocopherols, Tocotrienols, and γ-Oryzanol Contents in Japonica and Indica Subspecies of Rice (Oryza sativa L.) Cultivated in Brazil

¹Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of São Paulo. Av. Prof. Lineu Prestes, 580, São Paulo, SP, Brazil 05508-900. ²Department of Food Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70803. ³Corresponding author. E-mail: lanferum@usp.br

Whole rice contains several fat-soluble phytochemicals such as tocopherols, tocotrienols, and γ-oryzanol which have been reported to possess beneficial health properties. This study was conducted to determine whether brown rice belonging to indica and japonica subspecies were distinguishable from each other regarding the concentration of these compounds by analyzing 32 genotypes. The fat-soluble compounds were analyzed by normal-phase HPLC in a single run. The variability of the compounds analyzed was high, but the mean content of γ-oryzanol across all samples was significantly higher (P < 0.01) in japonica (246.3 mg/kg) than in indica rice (190.1 mg/kg). Similar differences were found for total vitamin E contents which were 24.2 mg/kg in japonica and 17.1 mg/kg in indica rice, respectively. In japonica rice, α-tocopherol, α-tocotrienol, and γ-tocotrienol were the most abundant homologs, while in indica rice the most abundant were γ-tocotrienol, α-tocopherol, and α-tocotrienol. A significant Pearson coefficient (0.80, P < 0.001) between α-tocopherol and α-tocotrienol levels was found, independent of the subspecies. Both compounds were positively correlated to total tocols and γ-oryzanol contents. Although more studies are needed to evaluate the interference of growing rice in different environments and multiple years, the present study provided information on natural variations of the vitamin E isomers and the γ-oryzanol contents in different rice genotypes.