## 3 Results
### LC-ESI+-MS, HPLC-DAD and Spectrometric Evaluation of Individual and Total Phenolic Derivatives  
For phenolic derivatives, by the LC-ESI+-MS analysis, the separation and identification of polyphenols was done, based on the retention times, peak areas and the \(m/z\) values for parental ions and fragments. In parallel, based on the calibration curves (Figure S1) of pure standards using the HPLC-DAD system, the retention times and peak areas were considered, and the concentration of individual compounds was determined. Concomitantly, the fast spectrophotometric FC method was applied for the quantitative evaluation and compared with the data obtained by HPLC-DAD. Table S7 includes the phenolic composition of individual oils, expressed in mg/100 mL oil according to the calibrations made for each category of phenolics, as presented in Figure S1 (Supplementary File). These data were obtained by HPLC-DAD (TP-LC) and compared with the values obtained by the spectrometric method.  
A large variety of phenolic derivatives were separated and identified in all samples, specific to each oil category, e.g., hydroxy benzoic and hydroxycinnamic acids (gallic, protocatechuic, vanilic, elagic, syringic and cafeic, coumaric, synapic, dicaffeoyl quinic, chlorogenic acids, respectively), flavonoids (quercetin, isorhamtein, luteolin, gallocatechin, daidzein, genistein), as well as lignans (pino- and matairesinols), tyrosols, oleuppein and juglone.  
The EVOO, SBO and SO were classified as \"high-phenolic\" oils compared to SFO, LSO, PO, HO, and WO. The TP values determined by HPLC-DAD were around three times superior to the values obtained by spectrometry (TP-FC), a result which is obvious considering that the FC method is based on the reducing capacity of free hydroxyl groups of  
Figure 4: (**a**) PLSDA score plot for the discriminatory analysis of the eight classes of oils, considering theirtocopherol contents. (**b**) Heatmap representing the Euclidian distance using the Ward algorithm to identify the similarities between individual oils.  
phenolics' and is not an accurate determination of all phenolic derivatives. As noticed also by other authors [47], we found high statistical correlation (\(p<0.005\)) between TP-HPLC and TP-FC values. Meanwhile, one should be considered that lignans and flavonoids do not show any linear relationship with FC data, suggesting caution about interpretation of FC results for oils having very different phenolic profiles.  
Based on LC-ESI+MS analysis and individual peak areas for each phenolic derivative, the multivariate analysis by PLSDA score plot shows a co-variance of 33.1% for the first two components, with good discrimination between EVOO, SBO and HO oils, the other oil groups showing less differentiation (Figure 5a). Figure 5b represents the heatmap which illustrates the specific composition of each oil category, according to their phenolic composition.  
Based on PLSDA analysis, the VIP scores showed the most significant 15 molecules to differentiate these oils. Therefore, SFO was specifically characterized by chlorogenic and dicaffeoylquinic acids, PO by vanillin and caffeoylquinic acid, LSO by matairesinol and pinoresinol, HO by canabigenol, SO by glyciten, daidzein and genistein, WO by juglone, ellagic acid and gallocatechin, EVOO by oleuropein, tyrosol and hydroxytyrosol, luteolin, pino-, matai- and acetoxipinoresinols, and SBO by many phenolic acids from hydroxybenzoic and hydroxycinnamic subclasses. Intuitive images are given by heatmaps of individual oils (Figure 5b), phenolics being good biomarkers to discriminate qualitatively and quantitatively the individual oil samples, as well the different categories of oils.