LC analyses were performed with Waters QSM Acquity, equipped with an UPTISPHERE Strategy C18 column (2.2µm x 150 mm x 2.1 µm, Interchim). The eluent consisted of H2O + 0.1% formic acid (A) and MeCN (B), following a gradient 5-30 % B in 4 min, then 30-80 % B in 14 min, then 80-100 % in 0.50 min, then maintaining 100 % B for 9.5 min at a flow rate of 0.5 ml/min. The wavelength range of the UV detector was set from 210 to 400 nm. Mass data were acquired with a Waters SYNAPT G2-Si (QTof) mass spectrometer. The electrospray ionisation source was set as follow: positive mode, source temperature 100°C, capillary 3 kV, desolvation temperature 450°C, nebuliser gas flow 5 Bar, desolvation gas flow 700 l/h. MS scans were performed in full-scan mode from m/z 100 to 1200 (scan time 0.1 sec) with a resolution of 40 000 (FWHM). An MS 1 scan was followed by MS 2 scans of the three most intense ions above a threshold of 3000 counts (exclusion window 3 sec). The selected parent ions were fragmented according to the following energy ramp: low mass start: 35 eV, low mass end: 55 eV, high mass start: 70 eV high mass end: 130 eV. Leucine-enkephalin (1 ng/µL) was used as a reference mass via a lock spray interface at a flow rate of 10 μl/min for positive ion mode monitoring ([M + H] + = 556.277).