Moderate Electric Fields as a Potential Tool for Sustainable Recovery of Phenolic Compounds from Pinus pinaster Bark

Abstract

Pinus pinaster (pine) bark is a widely available wood industry byproduct but an underexploited source of phenolic compounds with a strong antioxidant activity. The aim of this study was to evaluate the effectiveness of ohmic heating (OH, a recognized eco-friendly, electric fields-based processing technology) for the sustainable recovery of phenolic compounds from Pinus pinaster bark. Results of OH evidenced increased extraction of antioxidant phenolic compounds with no degradation of pine bark extracts for all tested conditions. Moreover, the enhancement in phenolic content in OH-assisted extraction was particularly evident when using a hydroethanolic solvent with 50% ethanol, reaching improvements higher than 100%, when comparing to the conventional approach. This fact may indicate preferential extraction, presumably due to the action of electric field effects acting in synergy with heat and solvents. Furthermore, additional changes in the morphological structure of bark cells were observed upon OH-assisted extraction, suggesting membrane electroporation effects. A significant reduction in energy consumption when compared with the conventional process was observed, leading to an energetically more sustainable approach. OH technology holds the potential to be a "green" alternative, with higher extraction yields and reduced energy consumption and offering the possibility of tuning the selectivity toward phenolic compounds.

Unravelling the Biological Potential of Pinus pinaster Bark Extracts

“…These results are in accordance with those described previously by our research group, where it was observed that P. pinaster bark extracts are very rich in phenolic compounds [5]. Moreover, Chupin et al [12] use P. pinaster bark and reported values from 236 to 306 mg GAE/g extract, depending on the extraction conditions, but the maximum was achieved with 80% ethanol.…”

“…The total content of phenolic compounds was measured by the Folin-Ciocalteu method that was based on the colorimetric reduction/oxidation reaction of phenols [5,20]. Gallic acid was used to perform the standard curve (R 2 = 0.996) and the results were expressed as milligram gallic acid equivalents (GAE) per gram of pine bark (optimization process) or dry extract (extract characterization).…”

“…Identification and quantification analysis of phenolic presents in PBE were performed as described previously [5] using a Shimatzu Nexpera X2 UPLC chromatograph equipped with Diode Array Detector (DAD) (Shimadzu, SPD-M20A, Columbia, MA, USA). Separation was performed on a reversed-phase Aquity UPLC BEH C18 column (2.1 mm × 100 mm, 1.7 µm particle size; from Waters, Milford, MA, USA) and a pre-column of the same material at 40 • C. The HPLC grade solvents used were water/formic acid (0.1%) and acetonitrile as eluents and the flow rate was 0.4 mL/min.…”

“…Three different methods of measuring the antioxidant activity were used: DPPH, ABTS and FRAP, as previously described by Ferreira-Santos et al [5].…”

“…The popularity of these extracts is linked to their biological properties, such as antioxidant, anti-inflammatory, antimicrobial, antiviral, antiatherogenic, etc. [3][4][5][6][7]. In particular, the extracts of Pinus pinaster (a conifer plant found in some Mediterranean countries and used in afforestation of Africa, New Zealand and Australia), are rich in phenolic acids, flavanols and flavonoids (e.g., cinnamic acid, hydroxybenzoic acid, catechin, quercetin and taxifolin) with a potent antioxidant activity [5,8].…”