An extraction method for determination of ginkgolides and bilobalide in ginkgo leaf extracts

On the basis of reversible ionization and intramolecular esterification, ginkgolides can be effectively removed from ginkgo extract products or from ginkgo leaves with boiling water containing 0.1% Na2HPO4 at pH similar to 8 followed by extraction of the aqueous phase with methylene chloride at pH similar to 5. Bilobalide can be quantitatively removed from these samples with just boiling water followed by the same liquid/liquid extraction. After derivatization with bis(trimethylsilyl)acetamide, these lactone terpenoids can be readily quantified using GC-FID with baseline separation. Using the proposed procedure, six different commercial Ginkgo biloba products were analyzed, and significant differences in their ginkgolide contents were observed.