Quantitative HPLC-DAD analysis of quercetin derivatives was performed on an HP 1100 HPLC (Agilent Technologies, Waldbronn,Germany) using a Nucleodur Sphinx RP-C18 column (125 4 mm;5 mm, Machery-Nagel, Düren, Germany) at 30 C The injection volume was 10 mL. The mobile phase consisted of a binary gradient with 5 ml/L formic acid in water (eluent A) and 100% acetonitrile (eluent B) with a flow rate of 1 ml/min