Composition and antioxidant properties of extracts from Douglas fir bark

Abstract

Abstract This study aimed to investigate the antioxidant ability and the chemical composition of apolar and polar extractives from Douglas-fir bark, cork and phloem, establishing a possible correlation with the structural variation along the tree stem and geographic location. Douglas-fir bark extractives’ composition were analyzed at three stem heights in trees from two locations. Cork and phloem extracts’ composition were analyzed in samples collected at stem base. Extractives content in Douglas-fir bark varied between 14 and 31% and polar extractives (11–29%) were dominant over non-polar. Lipophilic extracts were mainly composed of terpenoids, representing 27–77% of all compounds, highlighted by callitrisic acid (11–34%). Sterols were also abundant (6–45%), with β-sitosterol representing 7–33% of all compounds. Alkanoic acids were present in smaller amounts. Ethanol–water extracts showed high phenolic (562–762 mg GAE/g extract), flavonoid and condensed tannins contents (399–683 mg CE/g extract and 120–262 mg CE/g of extract), high scavenging (IC50 2.8 µg extract/mL) and reducing (12 mM Fe2+/g extract) abilities. Cork had high phenolic (819 mg GAE/g extract) and flavonoid contents (524 mg CE/g extract) and high antioxidant capacity (1080 mg TEAC/g extract). Detailed knowledge of Douglas-fir extracts demonstrates their potential as a source of fine chemicals towards different applications.