Optimised extraction of bioactive compounds from spruce needles for sustainable applications

Besides bark and branches, coniferous needles contribute to approximately 30 % of the biomass left unused in forests after timber harvesting, posing fire and environmental risks. However, by extracting valuable compounds from spruce needles, such as proanthocyanidins, phenolic compounds, shikimic acid, and others, targeted use of forestry by-product biomass can be achieved. Given the consumer demand for natural products and the growing need for alternative preservatives to ensure food safety, it is imperative that plant-derived components be fully assessed for their feasibility for food application. In this work extraction conditions for spruce needles were optimized using Response Surface Methodology, to obtain extracts with the highest concentration of bioactive compounds. The main identified and optimized extraction variables were temperature and time. Using the optimal extraction conditions allowed to extract a maximum concentration of phenolic compounds (79.21 ± 0.21 mg_GAE/g DM), proanthocyanidins (21.70 ± 0.24 mg_CE/g DM) and shikimic acid (32.4 ± 0.1 mg/g DM). Additionally, vitamins B₆ and B₉, in maximum concentration of 3.7 ± 0.14 µg/g DM and 4.35 ± 0.05 mg/g DM were obtained, respectively. The macro- and micro-nutrient composition of the extract obtained under optimal conditions was determined and the antibacterial characteristics against gram-positive food pathogens such as Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, were determined. Due to its rich composition of bioactive compounds, this extract stands out not only as a valuable and safe solution for use in sustainable food but can also be applied in the pharmaceutical field.