Abstract
γ-Oryzanol is a common designation of ferulated sitosterole or ferulated tritelpenalcohol. The major components of γ-oryzanol are β-sitosterol, cycloartenyl ferulate, 24-methylene cycloartanyl ferulate and campesteryl ferulate. γ-Oryzanol accounts for 0.04 % of the total weight of mature unpolished rice seed, but the function of γ-oryzanol during rice grain filling has not been elucidated. We extracted γ-oryzanol from whole rice seeds and determined changes in the contents and composition of γ-oryzanol by using HPLC at various stages of grain filling. Our results revealed that the biosynthesis of γ-oryzanol started at the early stage of grain-filling period and the accumulation of γ-oryzanol continued until the late stages of grain-filling period. In addition, the ratio of β-sitosterol decreased during grain filling, inversely that of cycloartenyl ferulate increased. On the basis of the results obtained, we will discuss the relationship between grain filling and γ-oryzanol content changes.
