## 3 Results and Discussions
### Phenolic Compounds  
Fourteen phenolic compounds were detected and quantified in the oleaster oils obtained from the three different populations. The identified phenolic compounds belong to five phenolic groups, namely, phenolic alcohols, flavonoids, secoiridoids aglycons, dihydroxybenzoic acids derivatives and phenolic acids (Table 5). The group of secoiridoids aglycons was the one present in greater quantities, imposed by the high ligstroside derivatives quantity that ranged from 271 mg/kg (Moncorvo location) and 359 mg/kg of oil (VNFC location), with statistical differences between both locations, and oleuppein aglycon (and derivatives) prevalence, with values between 227 mg/kg (Alijo location) and 261 mg/kg of oil (VNFC location), without statistical differences between locations. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Phenolic Compounds** & **Alijó** & **Moncorvo** & **Vila Nova de Foz Coa** &
\begin{tabular}{c} **One-Way ANOVA** \\ **(\(p\)-Value)**1 \\ \end{tabular} \\ \hline \hline
**Phenolic alcohols** & & & & \\ Hydroxytorsol (3.4-DHPEA) & 3.3 \(\pm\) 0.5 & 4.0 \(\pm\) 0.8 & 4.3 \(\pm\) 3.1 & 0.2997 \\ Tyrosol (\(p\)-HPEA) & 8.4 \(\pm\) 5.6 & 8.0 \(\pm\) 6.1 & 9.34 \(\pm\) 7.2 & 0.8271 \\ Hydroxytorsol acetate & 0.7 \(\pm\) 0.3  & 0.3 \(\pm\) 0.2  & 0.3 \(\pm\) 0.1  & \textless{}0.0001 \\
**Flavonoids** & & & & \\ Luteolin & 7.4 \(\pm\) 5.5 & 8.3 \(\pm\) 0.6 & 11.8 \(\pm\) 12.5 & 0.2687 \\ Apigenin & 9.4 \(\pm\) 5.5 & 12.0 \(\pm\) 2.5 & 13.2 \(\pm\) 5.5 & 0.0787 \\ Methyl-Luteolin & 0.6 \(\pm\) 0.4 & 0.6 \(\pm\) 0.6 & 0.5 \(\pm\) 0.5 & 0.5789 \\
**Secoiridoids** & & & & \\ Oleuppein aglycon (and derivatives) & 226.3 \(\pm\) 55.0 & 233.3 \(\pm\) 108.3 & 260.6 \(\pm\) 81.8 & 0.4845 \\ Oleuppein & 33.6 \(\pm\) 17.0  & 44.4 \(\pm\) 24.0  & 58.9 \(\pm\) 29.2  & 0.0165 \\ Ligstroide aglycon and derivatives & 287.5 \(\pm\) 83.8  & 270.6 \(\pm\) 95.9  & 358.8 \(\pm\) 107.8  & 0.0304 \\
**Dihydroxybenzoic derivatives** & & & & \\ Vanillin & 1.1 \(\pm\) 0.6  & 0.5 \(\pm\) 0.3  & 0.6 \(\pm\) 0.5  & 0.0077 \\
**Phenolic acids** & & & & \\ \(p\)-Cumaric acid & 5.3 \(\pm\) 2.0  & 10.7 \(\pm\) 8.8  & 6.9 \(\pm\) 3.2  & 0.0241 \\ \(\omega\)-Cumaric acid & 0.4 \(\pm\) 0.1 & 0.6 \(\pm\) 1.0 & 0.2 \(\pm\) 0.1 & 0.1114 \\ Cimamic acid & 14.9 \(\pm\) 7.5  & 14.7 \(\pm\) 4.8  & 24.0 \(\pm\) 8.7  & 0.0007 \\ Ferulic acid & 0.6 \(\pm\) 0.2 & 0.6 \(\pm\) 0.4 & 0.4 \(\pm\) 0.2 & 0.0932 \\
**Phenols** & 602.7 \(\pm\) 151.9 & 612.0 \(\pm\) 216.8 & 751.9 \(\pm\) 221.5 & 0.0705 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Phenolic composition (mg/kg of oil) of oils extracted from oleaster (mean \(\pm\) standard deviation) collected from different geographical locations (Alijó. Moncorvo and Vila Nova de Foz Coa). Different lower case letters mean significant statistical differences at a 5% significance level (one-way ANOVA followed by the [PERSON]’s multi-comparison test). Oleuropein aglycon and derivative forms were the second most represented group of compounds. The third most abundant compounds, oleuropein, showed statistically higher contents (\(p\)-value = 0.0165) in the oils from VNFC location (58.9 mg/kg of oil) than those quantified in the oils from Alijo location (33.6 mg/kg of oil) (Table 5). In the group of phenolic alcohols, tyrosol (\(p\)-HPEA) ranged from 8.0 mg/kg of oil (Moncorvo location) and 9.4 mg/kg of oil (VNFC location). Together with hydroxytyrosol acetate, these were the only significantly different phenolic alcohols between populations, with highest values observed for Alijo location. Among the identified flavonoids, apigenin (9.4-13.2 mg/kg of oil) showed higher values compared to luteolin (7.4-11.8 mg/kg of oil) and methyl-luteolin, with statistical differences between oleaster populations. Similarly, luteolin and apigenin were the major flavonoids found in oleaster oils from Algeria [7]. In the group of dihydroxybenzoic acid derivatives only vanillin was found, in significantly higher amounts for oils produced from Alijo population (1.06 mg/kg of oil).