Characterization of extractives from biomasses of the alpine forests and their antioxidative efficacy

Abstract

Tree species typical of the alpine forests can be valued not only as sources of timber, but also as raw tissues for the recovering of extractives with significant antioxidant activity (AA). To improve knowledge about the extractive content in these trees and to investigate whether there is a correlation between extract composition and AA, heartwoods, sapwoods, barks, knotwoods, twigs and needles of seven of the most common tree species from the alpine region were extracted with different solvents by Accelerated Solvent Extraction (ASE). The extracts were characterized by GC–MS for fatty and resin acids, TD-GC/MS for terpenes, HPLC-UV for phenolic monomers and condensed tannins (CT), and GC-FID for mono- and polysaccharides. The AA of the extracts were thereafter estimated using the DPPH assay.The exact composition of extractives derived was highly characteristic of each specific plant tissue, and some general trends were observed. The richest tissues in extractives (18.6–39.0% on dry tissue) were barks and needles. However, sapwoods showed a very low presence of extractives (5.2–7.5%). The main extractable compounds from bark were CT and polysaccharides, while phenolic monomers and monosaccharides represented the majority of needle extractives. Terpenes were mostly detected in twigs. The composition of extractives for heartwoods and knotwoods were more scattered and closely associated to the tissues.A significant correlation between the extract composition and their AA was demonstrated by a multiple linear regression analysis (p-value <0.001). The most effective compounds contributing to the high AA of the extracts were CT. Plant tissue rich in condensed tannins like European oak heartwood, Scots pine bark and Norway spruce bark, should therefore be considered as the most suitable sources for natural antioxidants from the alpine region. However, the findings need to be validated with further antioxidant assays.