Extraction and isolation of shikimic acid from Ginkgo biloba leaves utilizing an ionic liquid that dissolves cellulose

摘要

Shikimic acid (1, Fig. 1), first isolated from the fruit of the Japanese plant Illicium religiosum (Shikimi-no-ki) by Eijkman in 1885,1 is the starting material for the commercial synthesis of oseltamivir phosphate (Tamiflu®), which is widely used as an important antiviral agent for the H5N1 strain of influenza.2 Numerous medicinal plants contain shikimic acid 1 since it is an important biochemical intermediate in the biosynthesis of the amino acids phenylalanine, tyrosine and tryptophan3,4 as well as alkaloids, flavonoids and lignin.5 As the most significant commercial source of 1, star anise (I. verum), collected in Southern China, is known to be a rich natural source for 1 (3.3% w/w).6 Although recent concerns over a pandemic of the H5N1 flu have raised demand for the medicine, quantities of shikimic acid 1 still remain limited due to the amount of available star anise. Potential alternative resources of 1 for the production of oseltamivir phosphate are thus urgently required. Ginkgo biloba is one of the oldest living plants (called a "living fossil"), and its extracts have been used throughout the world as phytomedicines and effective dietary supplements.7