Determination of trace amounts of ginkgolic acids in Ginkgo biloba L. leafextracts and phytopharmaceuticals by liquid chromatography-electrospray mass spectrometry

Ginkgolic acids (GAs) are toxic phenolic compounds present in the fruits an d leaves of Ginkgo biloba L. (Ginkgoacae). Their maximum level in phytophar maceuticals containing ginkgo extracts has been recently restricted to 5 mu g/g by the Commission E of the former Federal German Health Authority. In order to detect ginkgolic acids at these low levels, a sensitive and select ive analytical method, based on liquid chromatography-electrospray mass spe ctrometry (LC-ES-MS) has been developed. The three main phenolic acids (1-3 ) of the chloroform fruit extract were isolated and used as standards for q uantification. In the LC-ES-MS negative ion mode, calibration curves with g ood linearities (r=0.9973, n=6) were obtained in the range of 0.5-10 mu g/g for compounds 1, 2 and between 0.1 and 7.5 mu g/g (r=0.9949, n=6) for gink golic acid 3. The detection limits at a SIN ratio of 3 were 0.1 (3) and 0.2 5 mu g/g (1, 2). Recoveries were around 101% at 5 mu g/g for the substances detected in the leaf extracts. Good precision was achieved with relative s tandard deviations of less than 4% (n=6). The optimised method was applied to verify whether the amount of gingkolic acids was below 5 mu g/g in a sta ndardised leaf extract which is a constituent of a phytopreparation. (C) 20 00 Elsevier Science B.V. All rights reserved.