Spruce Bark as a Source of Antioxidant Active Substances

The antioxidant potential of extracts from spruce bark was studied after Soxhlet extraction with ethanol and n-hexane. Ethanol spruce bark extracts were pre-extracted with a mixture of ethanol and n-hexane in a ratio of 1:5. Residues of the extracts and pre-extracts were added to lard (200 mg/kg) to examine its influence on oxidation stability of lard. The composition of the bark extractives was analyzed by GC/MS. The highest antioxidant activity was observed in the original ethanol extracts (15.0 mmol/mg), which had greater antioxidant activity than alpha-tocopherol (13.9 mmol/mg). The n-hexane extract from the spruce bark had 70% less antioxidant activity than the ethanol extract. The high antioxidant activity of the ethanol extract was due to the presence of resin acids (35%) and stilbenes (12%). These antioxidant-active substances increased the oxidation stability of the lard by 5 h, while the n-hexane extract increased the oxidation stability by only 0.5 h. The spruce bark was found to be an alternative feedstock of compounds with potential for use in foodstuffs as antioxidant.