Serum fructose concentration in rats after single dose oral administration of Si-Wu-Tang

Our previous study showed that fructose is an important active constituent that is responsible for Si-Wu-Tang's (SWT) effects promoting hematopoiesis and immunity. In order to provide primary data for analysis of the mechanism of fructose's bioactivity, the concentration of serum fructose in rats after a single oral administration dose of Si-Wu-Tang was determined. The concentration of serum fructose in fasting rats was 0.34 ± 0.24 mg/dL. After oral administration of 7.2 mL per kg body weight of SWT extract (1 mL extract corresponds to 1 g SWT dried herbs), serum fructose levels reached a peak concentration of 1.03 ± 0.25 mg/dL within 60 min, and then declined to the baseline level within 180 min, a pattern which is similar to the one reported for oral administration of pure fructose. The peak concentration was only 2-3 times higher than the baseline serum fructose concentration. These results showed that the increase of blood fructose concentration after oral administration of SWT is small and transient, which is very probably due to the quick metabolism of fructose by the liver. We suggest, for future research, it is necessary to consider the probability that fructose's bioactivity on hematopoiesis and immunity is not exerted by fructose in its original form, but after it is metabolized by the liver.