## 4 Conclusions  
The present study highlights promising insights on the chemical composition and related antioxidant and antibacterial activities of _P. pinaster_ Ait. and _P. pinea_ L. bark polar extracts. Indeed, the _P. pinea_ L. bark polar fraction has demonstrated higher abundances of total phenolic and proanthocyanidins, as well as of quinic acid and phenolic compounds identified by UHPLC-DAD-MS\({}^{\prime\prime}\) analysis, in comparison to that of _P. pinaster_ Ait. Moreover, quinic acid (**1**) and three phenolic compounds, namely an isomer of (epi)gallocatechin-(epi)catechinic dimer (**9**), protocatechuic acid (**2**), and quercetin (**15**), have been described herein, for the first time, as _P. pinea_ L. bark components. Interestingly, both studied pine bark extracts have exhibited similarly effective reducing power and scavenging effects against DPPH and ABTS free radicals, being comparable to Trolox and ascorbic acid. Considering the current emergence in searching for alternative antibacterial agents, _P. pinaster_ Ait. and P. pinea_ L. bark polar extracts have revealed bactericidal effects, at the 3.13-25 mg mL\({}^{-1}\) concentration range and at 25 mg mL\({}^{-1}\), against _S. aureus_ and _E. coli_ growth, respectively. Synergisms between quinic acid and the phenolic compounds, or even with the components of the other extracts, may have promoted the bioactivities of the pine bark polar extracts. Although there are several commercial _P. pinnster_ Ait. bark extracts with nutraceutical usage, this knowledge can provide prospective innovative food and cosmetic applications for the studied agroforest by-products, especially with regard to the _P. pinea_ L. bark. Nevertheless, the use of alternative solvents, such as natural deep eutectic solvents, for the extraction of quinic acid and phenolic compounds from _P. pinnster_ Ait. and _P. pinea_ L. barks is a further important step forward for their sustainable exploitation.  
The following are available online at [[https://www.mdpi.com/article/10.3390/app12020784/s1](https://www.mdpi.com/article/10.3390/app12020784/s1)]([https://www.mdpi.com/article/10.3390/app12020784/s1](https://www.mdpi.com/article/10.3390/app12020784/s1)), Figure S1: mass fragmentation of (epi)gallocatechin-(2\(\rightarrow\)O7, 4\(\rightarrow\)8)-(epi) catechchin in the negative ionisation mode, Table S1: _S. aureus_ counts after application of _Pinus pinster_ Ait. and _Pinus pinea_ L. bark polar extracts, Table S2: _E. coli_ counts after application of _Pinus pinster_ Ait. and _Pinus pinea_ L. bark polar extracts.  
Conceptualization, P.A.B.R., S.A.O.S. and A.J.D.S.; methodology and formal analysis, P.A.B.R., C.P., A.P.G. and R.T.N.; investigation, P.A.B.R., C.P., A.P.G. and R.T.N.; writing--original draft preparation, P.A.B.R.; supervision, S.A.O.S., A.M.S.S., A.A. and A.J.D.S. All authors have read and agreed to the published version of the manuscript.  
This work was developed within the scope of the projects CICECO--Aveiro Institute of Materials (UIDB/50011/2020 and UIDP/50011/2020), LAQV-REQUIMTE (UIDB/50006/2020 and UIDP/50006/2020), and CESAM (UIDP/50017/2020+UIDB/50017/2020+ LA/P/0094/2020), financed by national funds through the FCT/MCTES; co-financing, when adequate, by FEDER under the PT2020 Partnership Agreement. P.A.B.R., A.P.G., and S.A.O.S. acknowledge the \"AgroForWealth\" project (CENTRO-01-0145-FEDER-000001) funded by Centro2020, through FEDER and PT2020 for the post-doctoral grant of P.A.B.R. and A.P.G. and S.A.O.S. contracts. C.P. was supported by a junior research contract (CEEC individual/03974/2017) financed by FCT.  
The authors declare no conflict of interest.