**3. Results**

### *3.1. Identification of Phytochemical Compounds of Artichoke By-Products by HPLC-ESI-TOF-MS*

The compounds were identified by the data provided by the HPLC-ESI-TOF-MS instrument. Thus, for all the peaks detected in the chromatogram, a list of possible molecular formulas was obtained with DataAnalysis 4.0 software. The identification was achieved comparing with the data previously reported in databases and literature for artichoke composition.

The bibliography search consulted for the tentative identification of the detected compounds was composed by studies carried out on artichoke. Therefore, one of the studies reported the inflorescence of artichoke, which were lyophilized and extracted by ultrasound-assisted extraction (UAE) using 80% methanol as solvent [21]. Other authors evaluated the phenolic profile of the edible parts of artichokes (receptacle and internal bracts) using a conventional procedure and mixture of solvents, concretely sonication in methanol/water (70:30, v/v) [10,22]. Finally, another study was based on the study of the chemical composition of artichoke by-products (leaves, floral stems, and bracts) applying maceration with 80% methanol–water mixture able to obtain extracts enriched in polar compounds [18].

Figure 1 shows a representative base peak chromatogram (BPC) of artichoke byproducts PLE extract obtained by HPLC-ESI-TOF-MS analyzed in negative polarity. Moreover, Figure 2 includes the extracted ion chromatograms and mass spectra of the major phenolic compounds characterized in those extracts. Furthermore, Table 2 summarizes the main peaks detected according to their elution order, including the information provided by the MS spectrometer: experimental and theoretical *m/z*, error (ppm), molecular formula, proposed compound, and the PLE condition in which each of them was detected. As can be observed, a total of 23 compounds were detected, being 19 of them tentatively identified. Despite the information provided by the analyzer and the effort made for their identification, unfortunately four compounds remain unknown (listed as UK in Table 2). The proposed compounds were tentatively identified as phenolic acids, flavones, and derivatives (flavonoids), saponins, lipids, and other polar compounds. In the following sections, the tentatively identification of these compounds has been described according to these chemical sub-classes.


**Table 2.** Phenolic and other polar compounds characterized in *Cynara scolymus* L. PLE extracts analyzed by HPLC-time-offlight mass spectrometry with an electrospray interface (ESI-TOF/MS).


**Table 2.** *Cont.*

(\*) Indicate that these compounds were identified in all the PLE extracts. For those compounds that were not identified in all the extracts, the number of the PLE experiment in which they were detected was annotated. UK, unknown.

**Figure 1.** Base peak chromatogram (BPC) of representative pressurized liquid extraction (PLE) extracts of *Cynara scolymus* L. by-products.

### 3.1.1. Phenolic Acids

Peak 2, with a precursor ion at *m/z* 353.0878 was identified as chlorogenic acid [21], whereas peak 4, with *m/z* 359.0772 and a molecular formula C18H16O8, was proposed as rosamarinic acid [22]. Moreover, peaks 5 and 8, which displayed a *m/z* 515.1195 and retention times of 7.36 and 8.08 min, respectively, were identified as cynarin isomers, also named "dicaffeoylquinic acid isomers" [21,22].
