Supercritical-fluid extraction of bilobalide and ginkgolides from Ginkgo biloba leaves by use of a mixture of carbon dioxide, methanol, and water

Supercritical-fluid extraction (SFE) with pure carbon dioxide and with carbon dioxide modified by addition of methanol, ethanol, or water have been used to extract bilobalide and ginkgolides A, B, and C from Ginkgo biloba leaves. Each extract was analyzed by HPLC-ESIMS. Although addition of methanol or ethanol led to enhanced SFE yields of the compounds compared with use of pure carbon dioxide, the amounts extracted were only 10% those obtained by extraction with an organic solvent such as methanol or acetone-water 1:1. Addition of small amounts (4%, v/v) of water as modifier of the carbon dioxide, however, led to a dramatic improvement in the extraction yield of the compounds - to amounts which were 80 - 150% of the yields obtained by extraction with organic solvent. In addition, levels of ginkgolic acids, the toxic constituents of Ginkgo biloba leaves, extracted by SFE with carbon dioxide-methanol-water 80:16:4, were substantially lower after continuous pre-extraction with n-hexane and with pure carbon dioxide.