DETERMINATION OF GINKGOLIDES AND BILOBALIDE IN GINKGO-BILOBA LEAVES AND PHYTOPHARMACEUTICALS

A method has been developed for the determination of the pharmacologically active terpenoids ginkgolide A, B and C and bilobalide in Ginkgo biloba leaves and phytopharmaceutical preparations containing ginkgo extracts. The leaves (400-800 mg) are selectively extracted with methanol-water (10:90) and the resulting extract is purified by means of a polyamide and a C18 solid-phase extraction column. After concentration, the terpenoids are determined by high-performance liquid chromatography on a C18 column with methanol-water (33:67) as eluent and refractive index detection. Benzyl alcohol is used as an internal standard. The recovery of the method is 95 +/- 5%. The reproducibility is dependent on the concentration and varies from 2 to 15%. The minimum concentration that can be determined in leaves is 10-mu-g of terpenoid/g of dry leaves. With a small modification the method can be used equally well for phytopharmaceuticals. Several ginkgo medicines were investigated and the total concentration of terpenoids was found to vary by a factor 18. The concentration in leaves varied by a factor 40.