Preparation method of ginkgolide L

A ginkgolide type compound which serves as a powerful antagonist of platelet activating factors (PAF) has very good protective effects on focal cerebral ischemia and diffuse total cerebral ischemia. Ginkgolide is divided into ginkgolide A, ginkgolide B, ginkgolide C, bilobalide, ginkgolide K, ginkgolide L and the like. The content of ginkgolide L in ginkgo leaves is extremely low, so that ginkgolide L is difficult to obtain, and research report on ginkgolide L is nearly zero. The invention relates to a preparation method of ginkgolide L. Ginkgolide L is extracted from commercially available ginkgo total lactone or ginkgo total lactone obtained based on a known method. The preparation method is simple to operate, the raw materials are low in cost, a plenty of ginkgolide L can be obtained rapidly, and basis is provided for research on ginkgolide L.