Submitted to: Rice Utilization Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 1, 2007
Publication Date: December 15, 2007
Citation: Chen, M., Bergman, C.J. 2007. Rice grain vitamin-E homologs and g-Oryzanol: effects of grain development and cultural practices. Rice Utilization Workshop Proceedings.
The bran layer of the whole grain rice contains potential health-beneficial compounds. These include vitamin E homologs (tocopherols, tocotrienols), gamma-Oryzanols, simple phenolics and poly-phenolics. These are antioxidants which are believed to provide protection against diseases such as cancer and cardiovascular disease. Objective of this research was to study the accumulation of tocopherols, tocotrienols, and g-oryzanol during the grain development to gain better understanding of their biosynthesis. The developing grains of Cypress (tropical japonica) and Teqing (indica) were harvested every three days starting from 10 days-after flowering to post-maturity. The dried seed weight, content of chlorophyll, tocopherols, tocotrienols and g-oryzanol were determined. The contents of total tocopherols, tocotrienols, and g-oryzanols were accumulated at different rates between 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 g-oryzanol accumulation patterns synchronized with grain weight or dry mass accumulation. This suggested that the possible function of tocotrienols and g-oryzanols was for the protection of lipids from oxidative damage, and that the tocopherols and tocotrienols might have different metabolic pathways and functions for the developing and matured grain. The increasing knowledge showing the health benefits of tocotrienols and g-oryzanol, and their accumulation patterns in the developing grain indicate these two families of antioxidants are good targets for enhancing their levels through breeding.