Flavonoid recovery and stability from Ginkgo biloba subjected to a simulated digestion process

Absorption from the diet is normally a prerequisite for the potential in vivo beneficial role of flavonoids. Antioxidant activity of flavonoids in vitro has been the subject of several studies, and important structure-activity relationships of the antioxidant activity have been established. However, there is still debate about the stability and absorption of polyphenols under gastrointestinal conditions. Ginkgo biloba, a product well known for its flavonoid content, was chosen for this study. Ginkgo biloba leaves, standardised leaf extract EGb 761 and commercial tablets (containing EGb761) were incubated in simulated gastrointestinal fluids to determine the stability of their flavonoid profiles. The experiment was designed to mimic the human gut condition. HPLC analysis was then conducted to determine the resulting breakdown compounds and intact flavonoids after the incubation, thus indicating those compounds likely to be available for absorption. The different samples seem to react differently to the simulated digestion process. The results indicate a trend of conversion from the glycosides to the aglycones for some samples and subsequent degradation of the aglycones. This may indicate a need to further investigate the reported benefits of Ginkgo flavonoids as in vivo antioxidants and/or to consider the antioxidant activity of the resulting digestion-derived compounds. (C) 2003 Elsevier Ltd. All rights reserved.