Abstract
Reported for its antioxidant, anti-inflammatory and non-toxicity properties, the hot water extract of Picea mariana bark was demonstrated to contain highly valuable bioactive polyphenols. In order to improve the recovery of these molecules, an optimization of the extraction was performed using water. Several extraction parameters were tested and extracts obtained analyzed both in terms of relative amounts of different phytochemical families and of individual molecules concentrations. As a result, low temperature (80 °C) and low ratio of bark/water (50 mg/mL) were determined to be the best parameters for an efficient polyphenol extraction and that especially for low molecular mass polyphenols. These were identified as stilbene monomers and derivatives, mainly stilbene glucoside isorhapontin (up to 12.0% of the dry extract), astringin (up to 4.6%), resveratrol (up to 0.3%), isorhapontigenin (up to 3.7%) and resveratrol glucoside piceid (up to 3.1%) which is here reported for the first time for Picea mariana. New stilbene derivatives, piceasides O and P were also characterized herein as new isorhapontin dimers. This study provides novel information about the optimal extraction of polyphenols from black spruce bark, especially for highly bioactive stilbenes including the trans-resveratrol.
Highlights
Black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) is an economically highly appreciated species of the Canadian boreal forest especially for the quality of its wood
We report here the Picea mariana bark extract as a rich source of these two compounds, the trans-isorhapontin reaching the concentration of 11971 mg/100 g of dry extract
We have demonstrated in this research that the chemical composition of hot water extracts of black spruce bark was affected by extraction parameters
Summary
Black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) is an economically highly appreciated species of the Canadian boreal forest especially for the quality of its wood. Black spruce bark, a by-product of wood transformation, is available in large quantities. Produced at around 920,000 dry metric tons per year in Québec, spruce bark is mostly burnt to produce energy. This biomass rich in bioactive molecules could benefit from new alternative solution for its management. Several other active compounds identified in black spruce bark extracts such as taxifolin, pinoresinol, isolariciresinol, mearnsetin, are known for their strong antioxidant and anti-inflammatory properties [1]. Recoverable through simple water extraction, trans-resveratrol and others bioactive polyphenols could become available from black spruce bark feedstock as potential active ingredients for cosmetics, functional foods or pharmaceuticals. Acute oral toxicity of black spruce bark hot water extract obtained from our laboratory was tested on Sprague-Dawley rats on Molecules 2017, 22, 2118; doi:10.3390/molecules22122118 www.mdpi.com/journal/molecules
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