The chromatographic analysis was performed on a Shimadzu
LC-10 HPLC system, equipped with a reverse-phase column
(Nucleosil C18,
∅4.6 mm
×
250 mm), thermostated at 40 ◦C, and
a UV–Vis detector (Shimadzu SPD 10A, = 280 nm). The analytes
were eluted isocratically at a flow rate of 1 mL/min, using
a water:acetic acid:n-butanol (350:1:10, v/v/v) mixture as the
mobile phase.