Evaluation of the antioxidant activities of different bio-oils and their phenolic distilled fractions for wood preservation

• Phenolic compounds are primarily responsible for the bio-oil antioxidant activity.
• Phenolic compounds with high boiling point possess higher antioxidant activities.
• Guaiacol and its derivatives are the most effective antioxidant phenolic compounds.

This research investigated the antioxidant activities of raw bio-oils produced from pine and oak wood species. The study also included the effect of the pyrolysis parameters on the properties of the bio-oils produced. In addition to raw bio-oils, phenolic fractions were further isolated from the bio-oils at two different temperature ranges (180–220 °C and 220–270 °C) by using spinning band distillation columns. The antioxidant activities of raw bio-oils and phenolic fractions were evaluated using the Trolox equivalent antioxidant capacity (TEAC) assay. The concentrations of phenolic compounds were determined by gas chromatography/mass spectrometry (GC/MS). The results of the assay showed that the antioxidant activities of the phenolic fractions are much higher than those of the parent bio-oils. GC/MS analysis results showed that o-guaiacol and its derivatives (4-methylguaiacol, 4-ethylguaiacol, and 4-propylguiacol), phenol, 3-methylphenol, 2,3-dimethylphenols, 3-ethylphenol, and eugenol are the most influential phenolic compounds on the antioxidant activity of the bio-oils and their distilled fractions.