## 3 Results and Discussions
### Sterols Composition  
The sterol composition found for the oleaster oils studied is given in Table 4. Among the sterols detected, \(\beta\)-sitosterol was the main sterol identified, followed by campesterol and stigmasterol. No differences were observed between populations for these main compounds. Nevertheless, the percentage of \(\Delta\)-7-estigmastenol (0.76%) of oils from Alijo location was significantly higher (\(p\)-value = 0.0384) than the values observed for oils of Moncorvo and VNFC populations (Table 4). The percentage of triterpene alcohols from Alijo location (0.47%) were significantly lower (\(p\)-value = 0.0265) than those observed for Moncorvo (0.75%) and VNFC (0.69%) populations. Additionally, total sterols were remarkably higher than the statutory minimum limit (1000 mg/kg of oil) for olive oil and were significantly (\(p\)-value = 0.0124) higher for Alijo samples (2199 mg/kg) and lower for Moncorvo location (1742 mg/kg). Indeed, the contents of all sterols respects the established limits for olive oil with the exception of \(\Delta\)-7-estigmastenol (varying 0.61 to 0.76%), slightly above the legal maximum (0.5%) defined in the Commission Regulation (EEC 2568/91). It should be remarked that high levels of total sterols indicate that the oils are of high quality.  
Additionally, low values of triterpene alcohols indicate that the fruits are of good quality, and that good production practices were applied during the extraction process, namely a low extraction  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sterols Composition** & **Olive Oil 1** & **Alijó** & **Moncorvo** & **Vila Nova de** & **One-Way ANOVA** \\  & & & & & **Foz Cóa** & **(\(p\)-Value) 2** \\ \hline Cholesterol & \(\leq\)0.5\% & \(0.05\pm 0.02\)2  & 0.0040 \\ Brassicasterol & \(\leq\)0.1\% & \(0.03\pm 0.00\)2  & 0.0012 \\ Campesterol & \(\leq\)4.0\% & \(3.49\pm 0.54\) & \(3.69\pm 0.30\) & \(3.38\pm 0.91\) & 0.3807 \\ Stigmasterol & \(<\)camp & \(0.61\pm 0.13\) & \(0.79\pm 0.60\) & \(0.85\pm 0.61\) & 0.3599 \\ \(\beta\)-Sitosterol apparent 3  & 0.9376 \\ \(\Delta\)-7-Stigmastadienol & \(\leq\)0.5\% & \(0.76\pm 0.22\)  & 0.638 \\ Erythroidal and uvaol & \(\leq\)4.5\% & \(0.47\pm 0.21\)  & 0.75 \(\beta\)-st & \(0.69\pm 0.27\)  & 0.0265 \\ Total Sterols & \(\geq\)1000 mg/kg & \(2199\pm 464\)  & 0.0124 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Sterol compositions of oils extracted from oleaster (mean \(\pm\) standard deviation) collected from different geographical locations (Alijó. Moncorvo and Vila Nova de Foz Cóa).  
temperature and reduced time of malaxation. Furthermore, the sterolic fraction is a very useful parameter in the detection of adulterations, since it can be considered as a botanic origin marker [36]. In this case, the composition was very similar to olive oil once it is a variety of the same species (_O. europaea_ subsp. _europaea_ var. _sylvestris_) and oleaster oil is a rich source of phytosterols. This fact is of major relevance, since several biological activities have been attributed to phytosterols, mainly those related with the reduction of cholesterol absorption levels in the blood, sometimes being used in the treatment of hypercholesterolemia [5]. The amounts of total sterols quantified in the oleaster oils were in accordance with those reported in other studies, namely by [PERSON] [5], [PERSON] [11] and [PERSON] [36], with the exception of the levels of \(\beta\)-sitosterol, which could be related with the analytical methodologies used. On the other hand, once sterol content is influenced by several factors, such as climate, cultivar, geographical location and production practices [37] these aspects may also justify the differences observed in the amount of sterols.