Submitted to: Experiment Station Bulletins
Publication Type: Experiment Station
Publication Acceptance Date: July 1, 2007
Publication Date: July 12, 2007
Citation: Chen, M.H., Bergman, C.J., Pinson, S.R. 2007. Rice bran phytonutrients. Experiment Station Bulletins.
The bran layer of the whole grain rice contains potential health-beneficial compounds. These include vitamin E homologs (tocopherols, tocotrienols), oryzanol fractions, simple phenolics and poly-phenolics. These are antioxidants that are believed to provide protection against diseases such as cancer and cardiovascular disease. Human feeding studies demonstrated that the tocotrienol-rice fraction and oryzanol fractions of rice bran reduce serum cholesterol level, primarily by decreases in the LDL level. Studies also demonstrated that tocotrienols, rice bran phenolics and rice bran extracts were able to suppress proliferation of cancer in cell lines and in experimental animals. We studied the accumulation of tocopherols, tocotrienols, and oryzanol fractions during grain development. The developing grains of Cypress (tropical japonica) and TeQing (indica) were harvested every three days starting from 10 days-after flowering (DAF) to post maturity. The contents of total tocopherols, tocotrienols, and oryzanols were accumulated at different rates in the two cultivars. However, the accumulation patterns for each family of antioxidants were similar between the two cultivars. Total tocopherols accumulated to the maximum level during early grain development, and then dropped down to very low levels at grain maturity and post-maturity; while the total tocotrienols and oryzanol accumulation patterns were parallel with grain weight or dry mass accumulation and remained high post-maturity. This suggested that the possible function of tocopherols was for the protection of oxidative damage during rapid seed growth, and that the tocotrienols and oryzanol might have different metabolic pathways and functions for the developing and mature grain. The increasing knowledge showing the health benefits of tocotrienols and y-oryzanol, and their accumulation patterns in the developing grain indicate these two families of antioxidants are good targets for enhancing their levels through breeding.