The analyses were carried out using an Acquity UPLC system using an Acquity UPLC BEH C18 column (2.1mm×100mm, 1.7 μm particle size), both from Waters (Milford, MA, USA). The mobile phase consisted of 0.1 % (v/v) formic acid and ammonium formate 4 mM in water (eluent A) and 0.1 % (v/v) formic acid and ammonium formate 4 mMin methanol (eluent B). The analysis started with 95%of eluent A, which was kept constant during 1 min. Then, it was linearly decreased up to 0 % in 7 min. This composition was held during 4 min before returning to the initial composition in 0.5 min, followed by a re-equilibration time of 1.5 min, giving a total running time of 14 min. The flow rate was 0.3 mL min−1 and the column temperature was set at 30 °C. Aliquots of 5 μL of the sample extract were injected into the chromatographic system.