Elevated temperature during growth increases alpha‐tocotrienol and some but not all gamma‐oryzanol fractions in Arborio rice seeds

• Published in: The FASEB journal 2007-04, Vol.21 (5), p.A731-A731
• Main Authors: Britz, Steven J., Allen, L. Hartwell, Moreau, Robert A., Kremer, Diane F.
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.21.5.A731-b

Rice bran is a rich source of lipid‐soluble antioxidants including ferulylated phytosterols (i.e., γ‐oryzanol), tocopherols and tocotrienols. To evaluate the impact of temperature on the accumulation of these compounds, we grew rice from seed to maturity in replicate greenhouses in Gainesville, FL with temperatures ranging from near ambient at one end to approximately 4.5 °C above ambient at the other end. γ‐oryzanols, tocopherols, and tocotrienols were extracted from whole seed and analyzed by HPLC. α‐tocotrienol constituted about 20% of total tocols and was the only one to increase significantly both in absolute amount and as a proportion of total. Six γ‐oryzanol peaks, identified on the basis of absorbance maxima at 330 nm and co‐chromatography with an authentic γ‐oryzanol standard, were quantified. Peak 3 accounted for about half of all γ‐oryzanols and increased significantly by 30% at elevated temperature. Mass spectral evidence indicated this fraction was 24‐methylene cycloartenyl ferulate, a relatively early step in phytosterol metabolism. Peak 1, a minor component, also increased significantly; peaks 2, 4, 5, and 6 did not change. The results suggest the physiological action of individual ferulylated phytosterols should be investigated, since their relative proportions in γ‐oryzanol can change. This work was supported by the U.S. Dept. of Agriculture.