HPLC analyses were made with an Agilent 1200 series
rapid-resolution LC system equipped with a binary pump, an
autosampler, and a diode-array detector (DAD) following (Iswaldi
et al., 2012), and a Zorbax Eclipse Plus C18 analytical column
(150 4.6 mm, 1.8 lm particle size) was used for separation. The
mobile phases consisted of water:acetonitrile (90:10, v/v) with
1% formic acid (phase A) and acetonitrile (phase B) at a constant
flow rate of 0.5 ml/min using the following multi-step gradient:
0–20 min, from 5% B to 20% B; 20–25 min, from 20% B to 40% B