Extraction of flavonoid glycosides from Ginkgo biloba leaves and their adsorption separations using hydrophobic and anion-exchange membranes

In this work, the extraction of flavonoid glycosides from Ginkgo biloba leaves and their adsorption separation performance using C18 hydrophobic and strong anion-exchange membranes were investigated. First, the preparation of crude Ginkgo biloba L. extracts was carried out using 70% ethanol, and the effects of different extraction conditions were evaluated. The results show that the extraction temperature (50-70degreesC) and extraction time (1-5 h) did not significantly influence the performance, but a lower solvent amount (50g per 10g dry leaves) resulted in a better extraction. Before the adsorption separations, the extracts were dissolved in 30% ethanol to remove the undesirable biflavones and then used as feed solutions. Eighty percent ethanol was used as the eluent in the elution stage. Comparing the performances for different processes, higher yield for total flavonoid glycoside amount (46-60% for hydrophobic membranes and 39-53% for anion-exchange membranes) was accomplished in the batch process. On the other hand, a higher flavonoid glycoside content at the pinnacle fraction of elution peak (10 wt% for hydrophobic membranes and 7-13 wt% for anion-exchange membranes) and a shorter process period were achieved in the flow process.