CONCENTRATION OF GINKGOLIDES AND BILOBALIDE IN GINKGO-BILOBA LEAVES IN RELATION TO THE TIME OF YEAR

The concentrations of ginkgolides A, B, and C, and bilobalide were determined in the leaves of 3 different Dutch Ginkgo biloba trees from late spring until late autumn 1990. The concentration versus harvest time plots were roughly the same for all the compounds in each of the 3 trees. Concentration was lowest in spring and then gradually increased until a maximum in late summer or early autumn was reached. Thereafter the concentration declined until leaf fall. The difference in ginkgolide and bilobalide content between the 3 trees was very high. For ginkgolide B, the pharmacologically most potent compound, the maximum concentration was less than 3, 68 and 204 ppm respectively. Possible reasons for these differences and consequences for phytotherapy are discussed briefly.