IDENTIFICATION OF GINKGO-BILOBA FLAVONOL METABOLITES AFTER ORAL-ADMINISTRATION TO HUMANS

An extract of Ginkgo biloba leaves (EGb) was given to healthy voluntee rs. Urine samples were collected for 3 days, and blood samples were wi thdrawn every 30 min for 5 h. The samples were purified through SPE C- 18 cartridges and analyzed by reversed-phase LC-diode array detection for the presence of EGb metabolites. Only urine samples contained dete ctable amounts of substituted benzoic acids, i.e., 4-hydroxybenzoic ac id conjugate, 4-hydroxyhippuric acid, 3-methoxy-4-hydroxyhippuric acid , 3,4-dihydroxybenzoic acid, 4-hydroxybenzoic acid, hippuric acid and 3-methoxy-4-hydroxybenzoic acid (vanillic acid). In contrast to rats n o phenylacetic acid or phenylpropionic acid derivatives were found in urine, thus indicating that in humans a more extensive metabolism take s place. As for rats the metabolites found in human urines accounted f or less than 30% of the flavonoids given. The same procedure was appli ed to blood samples, and no metabolites could be detected.