HPLC was performed using a Phenomenex IB-Sil C-18 reversed phase column (250 mm x 3.2 mm, 5 μm diameter particles); flow rate 1 mL/min. The solvent system consists of 30 % to 60 % linear gradient of methanol in water over 25 min, 3 min isocratic, 100 % in 2 min, 4 min isocratic. UV absorption spectra were recorded at 254 nm.