Absorption, Distribution, and Excretion of Tagged Ginkgo Biloba Leaf Extract in the Rat

Abstract

The absorption, distribution and elimination of radiolabeled 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 radiolabeled 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 2-compartment model with an apparent first-order phase and a biological half-life of approximately 4.5 hours.During the first 3 hours , radioactivity was primarily associated with the plasma, but through a gradual uptake after 48 hours.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 labeled 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.