Chemical Characterisation, Antioxidant and Antibacterial Activities of Pinus pinaster Ait. and Pinus pinea L. Bark Polar Extracts: Prospecting Forestry By-Products as Renewable Sources of Bioactive Compounds

Abstract

Agroforestry by-products have gained rising attention in recent years as they represent inexpensive and abundant raw materials that are a source of added-value chemicals, e.g., for food and pharmaceutical applications, as well as for bioenergy generation. Pinus pinaster Ait. bark extracts are consumed worldwide for their cardiovascular benefits, whilst the health potential of Pinus pinea L. bark has not yet been deeply exploited. Therefore, this study highlights the chemical characterisation of Portuguese P. pinaster Ait. and P. pinea L. bark polar extracts, via ultra-high performance liquid chromatography-diode array detection-tandem mass spectrometry (UHPLC-DAD-MSn) analysis, and their antioxidant and antibacterial activities. Quinic acid, an A-type procyanidin dimer isomer, protocatechuic acid, and quercetin were identified for the first time as P. pinea L. bark components. Moreover, this bark demonstrated a higher total content of identified polar compounds than P. pinaster Ait. bark, with quinic acid being the most abundant compound identified. Regarding antioxidant activity, the pine bark polar extracts exhibited strong reducing power and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) radical scavenging effects compared to natural antioxidants. Moreover, the bactericidal actions of pine bark extracts were shown against Staphylococcus aureus and Escherichia coli at a 3.13–25 mg mL−1 range. Globally, these promising insights can boost the sustainable exploitation of P. pinea L. bark, as already occurs with P. pinaster Ait. bark, for the food and biomedical fields.

Microwave-Assisted Water Extraction of Aspen (Populus tremula) and Pine (Pinus sylvestris L.) Barks as a Tool for Their Valorization

“…Quinic acid was shown to have a positive influence on the antioxidant activity of the pine bark polar extracts. The reported content of quinic acid in the Pinus pinaster pine bark extract obtained by multi-step extraction with the application of dichloromethane for the removal of lipophilic compounds was 2.8% [21]. The application of microwave energy allowed for the obtention of the same content of quinic acid in the extract by the one-step water extraction of Pinus sylvestris bark (Table 8).…”

“…Except for oligomeric proanthocyanidins, pine extract was shown to consist of quinic acid, protocatechuic acid, caffeic acid and the following flavonoids: catechin, taxifolin-O-hexoside and taxifolin (Table 6). These compounds are well-known constituents of pine bark extracts [11,18,21]. 6).…”

“…In contrast to the aspen bark water extracts, oligomeric proanthocyanidins (PAC) are the dominating components of the pine bark water extracts, constituting up to 95% of the extracts (Figure 8). According to the literature, the maritime (Pinus pinaster) and Pinus pinea pine bark extracts obtained by methanol/water/acetic acid (49.5:49.5:1, v/v/v) extraction after the removal of lipophilic compounds contain 81.4 and 85.7% of PAC, but the commercial pine bark extract Pycnogenol ® contains 70.0% of PAC [21]. At 70-90 • C, the content of proanthocyanidins in the MAE extracts is close to that in the ASE extracts obtained at optimal extraction times (four extraction cycles of 5 min each).…”

“…Pycnogenol ® , Flavangenol ® and Oligopin ® are trademarks of the commercially available extracts of maritime pine (Pinus pinaster) bark, which contains procyanidin dimers, trimers, oligomers and polymers, phenolic acids (e.g., protocatechuic, gallic, ferulic and caffeic acids), flavanones (e.g., taxifolin and taxifolin-3 -β-D-glucoside), etc. [19,21]. Pinus sylvestris L. bark is available as waste in large quantities in many countries and can be considered as an alternative source of high value-added products to Pinus pinaster bark [11,22].…”

“…Several constituents of pine bark extracts, such as gallic, protocatechuic acids and catechin, are readily adsorbed by human skin and make the preparations useful for topical application [19]. Synergisms between quinic acid and the phenolic compounds may have promoted the bioactivities of the pine bark polar extracts [21]. However, the high polymerization degree and high molecular weight of a significant part of bark proanthocyanidins make them unable to penetrate biological membranes effectively, limiting both their biological activity and range of applications [20].…”