Abstract: The method for determination of toxic components -ginkgolic acids in leaves of Ginkgo biloba by Ultraviolet spectrophotometry was established. The contents of ginkgolic acids in leaves of Ginkgo biloba collected within different vegetative periods were determined by UV and HPLC. The leaves of Ginkgo biloba were extracted by n-hexane in Soxhlet apparatus, then concentrated under vacuum. The ginkgolic acids could be determined directly by UV spectrophotometry at 242 nm and 310 nm after one-pre-purified-step by silica gel column chromatography. The linear regressive equations were A=1.55×10-4+16.36×C(R=0.999) and A=0.031+9.08×C(R=0.997) respectively. Their linear scope was 5.72～114.4 mg/L. The average recovery of ginkgolic acids was 97.6% and 97.5%,RSD was 2.1% and 2.4%(n=6) respectively. The results being detected at both wavelength were close to that by HPLC. The results showed that the content of ginkgolic acids in the leaves of Ginkgo biloba is relative to the vegetative periods ,and leaves of Ginkgo biloba are best collected in September. Not only is the method found to be simple ,fast and accurate,but has wide linear scope. The limit of detection can be up to 5.72×10-6. And it can be used for determination of toxic components-ginkgolic acids in the leaves and teas of Ginkgo biloba.

Key words: Leaves of gingko biloba , Teas of gingko biloba , Gingkolic acids , Ultraviolet spectrophotometry HPLC