The HPLC apparatus was Agilent 1100 system with chromatographic column Zorbax SBC-18 (5 μm, 150 mm × 4.6 mm); UV detector read at 215 nm; the temperature of column was 30 °C. The mobile phase was the mixture of 0.1% acetic acid: acetonitrile = 90:10; velocity flow was 1.0 mL/min; injection volume was 5 μL.