Representative chromatograms of EGCg (a) and PGG (b) at the beginning and end of the simulated digestion without added biomolecules. The top trace in each chromatogram is the sample collected immediately after the polyphenol was mixed with the mandelic acid and the pH 1.8 HCl-saline solution. The bottom trace is the sample collected after the sample had been incubated for 2 h at pH 7.0. In each case, the sample was collected, mixed with an equal volume of 1% SDS, and immediately analyzed by reversed phase HPLC with detection at 220 nm, using a gradient of acetonitrile-water modified with 1% trifluoroacetic acid. MA, mandelic acid (internal standard).