HPLC mass spectrometry was carried out on a HP HPLC series 1100 (Hewlett-Packard, Waldbronn,Germany) combined with a mass spectrometric detector Platform II (Micro Mass, Manchester, UK).Conditions: electrospray ionization (negative mode);source temperature 1208C; cone voltage ramp 10–50 V; acceleration lens potential 0.5 kV; m/z range 100–800; scan rate 0.4 scan/s, multiplier voltage 650 V