The HPLC system (Merck) was equipped with an L-7200
autosampler, a D-7000 interface module, an L-7100 pump, an L-
7350 column oven with Peltier cooling module, and an L-7450A
diode array detector. Reverse phase chromatography was performed
with a Kromasil C8 5 m column (150 mm
×
4.6 mm). HPLC
conditions were as follows: Solvent A was H2O with 0.05% TFA,
and solvent B was composed of methanol with 0.05% TFA. A linear
gradient was performed over 21 min from 5 to 35% B. The flow
rate was 1 mL/min, operated at 25 ◦C. The injection volume was
20 L. Elutions were