## 3 Results  
### Chemical Composition and Antioxidant Activity of Leaf and Pomace Materials  
Compositional data about the total phenol content (TPC) and flavonoid content (TFL), the levels of the main individual phenols and triterpene acids of the plant extracts, including antioxidant activity (DPPH\({}^{\bullet}\) and CUPRAC) are presented in Table 1.  
AL was the richest in total phenols and antioxidant constituents but significantly poorer in total flavonoids. In particular, TPC was 1.38-fold higher in AL than in OL, in contrast to results reported by [PERSON] et al. [8] (OL being 1.76-fold richer than AL). Its TPC was found to be much higher than that reported by other researchers for fresh avocado leaves [8; 27] (29 vs. 3.7-19.3 mg GAE/g fresh leaves). In the case of OL and OP extracts, TPC values varied within a typical range for their botanical sources [9]. HR-MS and LC-DAD analyses of AL extracts verified the abundance \begin{table}
\begin{tabular}{l c c c} \hline  & **AL** & **OL** & **OP** \\ \hline Colorimetry & & & \\ TPC (g GAE/kg dw) & 73.78 \(\pm\) 5.11 & 53.24 \(\pm\) 1.33 & 16.28 \(\pm\) 3.62 \\ TFC (g QUE/kg dw) & 3.92 \(\pm\) 0.21 & 10.17 \(\pm\) 0.33 & 0.61 \(\pm\) 0.01 \\ \hline HPLC analysis & & & \\ Oleeuropein (g/kg dw) & ND & 53.18 \(\pm\) 0.26 & ND \\ Luteolin-7-O- & ND & 3.33 \(\pm\) 0.00 & ND \\ glucoside (g/kg dw) & & & \\ Total flavonoids & 5.01 \(\pm\) 0.00 & 7.45 \(\pm\) 0.71 & ND \\ (g LUTE/kg dw) & & & \\ Chlorogenic acid & 13.56 \(\pm\) 0.04 & ND & ND \\ (g/kg dw) & & & \\ Verbascoside & ND & 3.86 \(\pm\) 0.05 & ND \\ (g CHAE/kg dw) & & & \\ Hydroxyytrosol & ND & ND & 3.21 \(\pm\) 0.03 \\ (g/kg dw) & ND & ND & 1.15 \(\pm\) 0.00 \\ Maslinic acid & ND & 4.54 \(\pm\) 0.05 & 6.05 \(\pm\) 0.01 \\ (g/kg dw) & & & \\ Oleanolic acid & ND & 17.49 \(\pm\) 0.28 & 1.80 \(\pm\) 0.03 \\ (g/kg dw) & & & \\ \hline Antioxidant activity & & & \\ AA (DPPH, mol & 0.56 \(\pm\) 0.01 & 0.25 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 \\ TE/kg dw) & & & \\ \hline AL = avocado leaves; OL = olive leaves; OP = olive pomace; TPC = total phenolic content; GAE = gallic-acid equivalents; TFC = total flavonoid content; QUE = quercetin equivalents; AA = antioxidant activity; TE = Trolox equivalents; LUTE = luteolin-7-O-glucose equivalents; ND = not detected. Results are expressed as mean value \(\pm\) standard deviation (\(n\) = 3). & \\ \hline \end{tabular}
\end{table} 
Table 1: Compositional and antioxidant activity data for avocado leaves, olive leaves, and olive pomace material used in this study. of a phenolic acid (Table 1, Figure S1), putatively identified as chlorogenic acid [28] (_m/z_ 353.0859 [M-H]\({}^{-}\), _m/z_ 191.0555 [M-H]\({}^{-}\) for quinic acid residue). The same compound prevailed in the phenolic composition of hydroalcoholic extracts from AL cv. Hass [8]. In our study, the AL (cv. Fuerte) extract probably contained traces of procyanidin B1 [29] (_m/z_ 245.0425 [M-H]\({}^{-}\)) and isoquercitrin (_m/z_ 463.0872 [M-H]\({}^{-}\)) or another kaempfer di-glucoside (_m/z_ 609.1478 [M-H]\({}^{-}\)). Quercetin-O-hexoside or other typical kaempfer derivatives that have been reported in the AL cv. Hass [8] were not detected. HPLC-profiling data provided further insight into the potential of those plant materials as sources of VAO oxidation inhibitors. OL extracts were rich in well-known chain-breaking antioxidants such as oleupropein, luteolin-7-O glucoside, and verbascoside. Significant amounts of oleanolic and mashinic acids were also found. Although these metabolites are known as intracellular antioxidants [30], they are not expected to be strong radical scavengers under common in vitro assay or autoxidation conditions. Maslinic and oleanolic acids were also present in the olive pomace (OP) extract that was found to be richer in simple phenols rather than flavonoids. Thus, hydroxytyrosol, being almost 3-fold higher than tyrosol, was the only strong antioxidant identified in OP [31]. Beyond TPC, the HPLC-profiling data better explained the trends in AA of the studied samples after intercomparison (Table 1).