THE METABOLIC FATE OF THE EFFECTIVE COMPONENTS OF RADIX PUERARIAEⅡ. THE ABSORPTION, DISTRIBUTION AND ELIMINATION OF ¹⁴C-DAIDZEIN.

The absorption, distribution and elimination of carbon-14 labelled daidzein(¹⁴C-daidzein) were studied in rats using filter paper-liquid scintillation counting method.The radioactivity began to appear in the blood 30 min after oral administration of ¹⁴C-daidzein, reached its peak in 6～8 hrs, and then decreased steadily. It was estimated that about 64.6% of the radioactivity was absorbed from the gastrointestinal tract within 24 hrs.After intravenous injection of ¹⁴C-daidzein, the blood level of radioactivity was found to decrease in two phases, namely the distribution phase and the elimination phase, with the T1/2 of 13 rain and 42 rain respectively. The level of radioactivity was highest in the kidney and liver, moderate in the plasma, lung and heart, and low in the skeletal muscle, spleen, testis and brain.After intravenous injection of ¹⁴C-daidzein, the majority (71.2%) of the radioactivity was excreted in the urine 24 hrs after administration, while only 17.4% was recovered from the faeces. However, after oral administration, the amount excreted in the urine and faeces was about equal, namely 34.3% and 33.1%, respectively.About 47.4% or 39.1% of the dose could be recovered from the bile 24 hrs after intravenous or oral administration, indicating that biliary excretion was one of the main routes of elimination.Gomparison of the results presented above with those reported in the previous paper using chemical method for the determination provides evidence that the radioactivity recovered from the gastrointestinal tract, urine and bile was mainly metabolites of daidzein. It implies that daidzein is metabolized rapidily in the body.