Task: Question Generation
Input (English): To research the methods of purifying polyprenol from leaves of Ginkgo biloba L..', 'The purity of polyprenol was determined by HPLC to select the optimal purifying conditions.', 'The optimal conditions were degreased by 160 times of petroleum ether-ethyl acetate (9:1) firstly, then through a silica gel column (100-140 mesh) and eluted with petroleum etherethyl acetate (19:1).
Output (English): Does [ Studies on purification of polyprenol from Ginkgo biloba L. leave ]?