Plant extracts purified by SPE were subjected to LC–ESI-MS/MS
analysis. This analysis was carried out on liquid chromatography
coupled with mass spectrometry (LC/MS) using a ThermoFisher
system in which HPLC (Surveyor) system was equipped with linear
ESI-Ion Trap (LTQ XL) Mass Spectrometer (ThermoFisher Scientific,
San Jose, CA, USA). Usually, 5 lL of sample was injected via an
autosampler (Surveyor autosampler plus) into the HPLC system
(Surveyor) equipped with reverse phase C-18 column (Phenomenex
250 mm, 5 lm particle size). Sample elution was carried out
at flow rate of 5 ml/min using gradient elution comprising Solvent
A (water: acetonitrile: trifluoroacetic acid ratio 90:10:0.1% (v/v))
and solvent B (water: acetonitrile: trifluoroacetic acid ratio
10:90:0.06% (v/v). Elution was performed using the following gradient:
0–10 min: 10–35% B, 10–20 min: 35–42% B and 20–30 min:
42–100% B. A photodiode array was used as detector. Prominent
peaks were analyzed by mass spectrometer (LTQ XL ThermoFisher
Scientific) using atmospheric pressure electrospray ionization (ESI)
probe at negative ion mode. Identification of phenols was conducted
under full scan mode in the range of 100–600 m/z. MS2
analysis for each parent ion peak was performed at different Collision
Induced Dissociation (CID) powers. X-calibur 1.4 software was
applied for calibration of MS data (Sun et al., 2007)