RESUMO
The absorption, distribution and elimination of a radiolabelled 14C extract prepared from Ginkgo biloba leaves have been studied in rats. Following oral administration, expired 14C-CO2 represented 16% of the administered dose excreted within the first 3 hours post-dose out of a total of 38% after 72 hours. An additional 21% of the administered dose was eliminated in the urine. The absorption of the radiolabelled Ginkgo biloba extract was at least 60%. The pharmacokinetics of the drug, based on blood specific activity data versus time course, were characteristic of a two-compartment model with an apparent first order phase and a biological half-life of approximatively 4.5 h. During the first 3 hours, radioactivity was primarily associated with the plasma, but through a gradual uptake after 48 h. The specific activity in erythrocytes matched that of plasma. A site of absorption in the upper gastrointestinal tract is suspected since specific activity in blood peaked after 1.5 hours. Glandular and neuronal tissues and eyes showed a high affinity for the labelled substance. These results provide the first tentative link between the therapeutic effectiveness of Ginkgo biloba extract and the biological fate of some of its constituents.
