## 2 Materials and Methods
### Antioxidant Activity  
_P. pinaster_ Ait. and _P. pinea_ L. bark polar extracts were evaluated regarding their antioxidant activities by three different methods, namely reducing power, DPPH and ABTS scavenging assays. Table 5 highlights the IC\({}_{50}\) values obtained for each extract. To the best of our current knowledge, the reducing power of the _P. pinaster_ Ait. and _P. pineae_ L. bark polar extracts was determined for the first time in the present study. The IC\({}_{50}\) of these extracts ranged between 21.21 ug mL\({}^{-1}\) of _P. pineae_ L. extract and 22.53 ug mL\({}^{-1}\) of _P. pinaster_ Ait. extract. Both pine bark polar extracts were slightly more efficient than the trolox (up to 1.4-fold) (_p_ < 0.05). Although the Ferric Reducing Antioxidant Power (FRAP) of phenolic-containing extracts, derived from the _P. pinaster_ Ait. bark, was previously addressed, the mechanisms underlying this assay differ from the reducing power approach used here. To the best of our current knowledge, only pine bark extracts from _P. bruttia_ (80% (_v_/_v_) methanol extracts) were assessed through the reducing power, evidencing a IC\({}_{50}\) range of 9.17-11.38 ug mL\({}^{-1}\)[43]. Thereby, both the _P. pinaster_ Ait. and the _P. pineae_ L. bark polar extracts were slightly less effective as reducing agents than those of the aforementioned _Pinus_ species (2.3-fold). The _P. pineae_ L. and _P. pinaster_ Ait. bark polar extracts demonstrated strong DPPH scavenging effects (Table 5), whose IC\({}_{50}\) values were, respectively, 6.46 and 6.79 ug mL\({}^{-1}\), which are slightly lower than that of ascorbic acid (3.96 ug mL\({}^{-1}\)). Considering the Antioxidant Activity Index (AAI), both pine bark polar extracts have shown much higher values (9.58 and 9.11 for the _P. pineae_ L. and _P. pinaster_ Ait. bark extracts, respectively) than those of the _P. pinaster_ Ait. bark aqueous (AAI = 0.53) and hydroethanolic (30-90% (_v_/_v_) ethanol) extracts (0.53-1.06 AAI range). Actually, the AAI of the analysed _P. pineae_ L. bark polar extract corresponds to up to 18.1-fold compared to the aqueous and 90% (_v_/_v_) ethanol extracts of another Portuguese _P. pinaster_ Ait. bark [10]. Moreover, the pine extracts tested herein have shown to be more active in scavenging the DPPH free radicals than the _P. pinaster_ Ait. bark aqueous, 50% (_v_/_v_) ethanol, and ethanol extracts (82.24-108.74 mg AAE g\({}^{-1}\) dry bark), achieving up to 1.5-fold [37]. Even considering the bark extracts of other pine species, the _P. pinaster_ Ait. and _P. pineae_ L. bark polar extracts characterised in the present work have shown better DPPH scavenging action than the extracts obtained by Soxhlet acetone/water (7:3, _v_/_v_) and microwave-assisted extraction of _P. radiata_ bark, with AAI ranges of 1.71-1.81 and 2.27-3.37, respectively [66]. The ABTS scavenging effect of _P. pineae_ L. bark extract was close to that of the _P. pinaster_ Ait. bark extract (Table 6), showing promising IC\({}_{50}\) values of 3.89 and 3.95 ug mL\({}^{-1}\), respectively. Compared with the antioxidant standards, both extracts were as active as ascorbic acid in scavenging ABTS\({}^{\bullet}\) but less active than Trolox in this assay (_p_ < 0.05). Considering the IC\({}_{50}\) values expressed as mmol Trolox equivalents (TE) per g of extract, the data represented here are concordant with those described in the literature for _P. pinaster_ Ait. bark water (4.35 mmol TE g\({}^{-1}\) of extract) [19] and alkaline extracts (4.70-5.38 mmol TE per g\({}^{-1}\) of extract) [40], but much stronger than ethanol extracts (28.8-fold) [10]. Moreover, both the studied extracts revealed similar ABTS scavenging actions compared to those of 80% methanol extracts, derived from _P. bruttia_ bark (0.65-1.12 mmol TE g\({}^{-1}\) dw) [43].