The mobile phase consisted of water-0.1% formic acid (A) and acetonitrile (B) and a linear gradient program of 10-30% B in 0-30 minutes, 30-100% B in 30-40 minutes was used at a flow rate of 0.8 mL/min and a setting of 347 nm for the DAD detector (Akowuah et al. 200 la, b).