## 4 Conclusions  
Within the present work, we intended to characterize the oleaster oils obtained from three distinct locations in Northeastern Portugal. The results showed that the different populations presented some morphological differences but a very similar oil composition, with only slight variations in some fatty acids, tocopherols, sterols and phenolic compounds that allowed discriminating the oils according to the location of origin. Fatty acid composition revealed that oleic acid (68.9-70.6%), followed by palmitic (14.2-14.7%) and linoleic acid (7.87-9.88%), were the most abundant, similarly to olive oils. \(\alpha\)-Tocopherol presented more than 90% of the tocopherols detected, with total tocopherol values ranging from 263 to 503 mg/kg of oil. \(\beta\)-Sitosterol was the major sterol observed, and total sterol values varied from 1742 to 2198 mg/kg of oil, again within olive oil regulation. Fourteen phenolic compounds from five families (dihydroxybenzoic derivatives, flavonoids, phenolic acids, phenolic alcohols, and secoiridoids,) were identified and quantified. Ligstroside derivatives (271-359 mg/kg of oil) and oleuppein aglycon and derivatives (227-261 mg/kg of oil) were the most abundant ones, which is of major relevance from a health point of view. Thus, it could be concluded that oleaster oils presented a chemical profile very similar to olive oil, largely enriched in compounds such as tocopherols, sterols and phenolics. Furthermore, it was found that the region is an important factor in the chemical composition of the studied oils. Although the profile is similar across all of them, the composition varied, with some being richer in antioxidant compounds than others, particularly the VNFC population, despite having the shorter fruits in the study. The rich composition of oleaster oils indicates that the characterized populations could be included in breeding programs to produce olive oils rich in bioactive compounds. Nevertheless, other aspects should be considered, such as fruit yield in oil, fruit size, susceptibility to pests and diseases, and suitability to mechanization. On the other hand, considering the market search for sensory and chemical differentiated products, the production of oleaster oils for commercial purposes could be envisaged.  
Figure 1: Discrimination of oleaster oils according to three geographical origins (\(\bullet\) Alijó; \(\blacktriangle\) Moncorvo; or, \(\blacksquare\) Vila Nova de Foz Coa) using a LDA-SA model based on the contents of eicosenoic fatty acid; SFA; erythroidoid and uvaol; hydroxytrosol acetate; and, cinnamic acid. The full lines represent the boundary lines based on the posterior probabilities calculated for each class membership.  
**Author Contributions**: Conceptualization: N.R., P.B. and J.A.P.; methodology: N.R., T.P., S.C. and A.M.P.; investigation: all authors; resources: S.C. and J.A.P.; writing--original draft preparation: N.R., S.C., A.M.P., P.B. and J.A.P.; writing--review and editing: S.C., A.M.P., P.B. and J.A.P. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020), and to REQUIMTE (NORTE- 01- 0145-FEDER-LAQV (UIDB/50006/2020). This work was also supported by PRODER project OliveOld--Identificacao e caraterizacao de oliveiras centenarias para obtencao de produtos diferenciados\" no. 53988. [PERSON] thanks to National funding by FCT--Foundation for Science and Technology, P.I., through the institutional scientific employment program-contract.  
**Conflicts of Interest**: The authors declare no conflict of interest.