The HPLC consisted of a Waters apparatus equipped with a 600 pump and pump controller, a Waters autosampler mod. 717, and a UV-Visible Photodiode array detector, mod 2996. For resveratrol determination, an isocratic chromatographic method was used. Mobile phase was composed by 80% of solvent A (10% acetic acid) and 20% of solvent B (acetonitrile). The HPLC column was a Symmetry C18 reverse phase (3.9 mm × 150 mm, 5 μm particle size, with a 10 mm guard column of the same material) and flow rate was 1 mL/min. Resveratrol quantitation was performed by peak area integration at 306 nm. Before the analysis, 20 μL of each sample was diluted 1:10 in mobile phase, filtered onto 0.2 µm filters, and then 50 µL were injected onto the column.
Calibration curve from 75 picomoles to 12 nanomoles was prepared by diluting in appropriate solvents a 20 mM stock solution of resveratrol in dimethylsulfoxide (DMSO). The curve (six data points, in duplicate) is linear with an R2 value of 0.999 (Figure 8 ). Peak detection (retention time: 6 min) and purity were checked with the photodiode array detector to verify the characteristic absorption spectrum of the polyphenol (Figure 8 , inset).
Calibration curve from 75 picomoles to 12 nanomoles was prepared by diluting in appropriate solvents a 20 mM stock solution of resveratrol in dimethylsulfoxide (DMSO). The curve (six data points, in duplicate) is linear with an R2 value of 0.999 (