Effect of the oral administration of γ-oryzanol on the levels of plant sterols in whole serum and HDL fraction was studied in 12 patients with hypercholesterolemia and it was examined whether the sterol fraction of γ-oryzanol is incorporated into HDL-cholesterol.
The sterol fraction of γ-oryzanol consisted of 21% campesterol, 11% β-sitosterol and 68% five other sterols. The plant sterols were found to react with the enzyme system for the determination of cholesterol, that is, campesterol and β-sitosterol reacted in the enzyme system at the rate of 48% and 88% of that of cholesterol, respectively, γ-Oryzanol itself did not react but its unsaponifiable matter reacted at the rate of 35% of cholesterol. It was therefore suggested that the free sterol fraction, which was considered to be the main form of γ-oryzanol in blood, may affect the determination of serum or HDL-cholesterol.
After the treatment with γ-oryzanol 300mg/day for 10 weeks, the concentrations of campesterol and β-sitosterol were increased by 43μg/dl and 15μg/dl in the HDL fraction, and 196μg/dl and 85μg/dl in whole serum, respectively. The sum of the increases of campesterol and β-sitosterol in the HDL fraction corresponded to 2% of the increase of HDL-cholesterol (2.8mg/dl) and that in whole serum corresponded to 6% of the increase of total cholesterol (4.6mg/dl).
These results indicated that the levels of plant sterols in the HDL fraction or whole serum must be taken into consideration in order to evaluate accurately the effect of γ-oryzanol on HDL-or total cholesterol.
