Ethanol organosolv lignin as a substitute for commercial antioxidants, focusing on the structural properties and synergistic effect with myricetin

•Antioxidant activity of ethanol organosolv lignin and synergy were investigated.•Phenolic-OH content was predominant factor in the antioxidant activity of the lignin.•Lignin with a higher phenolic-OH and a lower IC50 value covered wide synergy ranges.•Synergy with myricetin was verified by comparing predicted and actual values.•Phenolic-OH ratio of myricetin and the lignin for the synergy was suggested. Lignin has potential as a substitute for natural antioxidants in cosmetics and food industries due to its radical scavenging ability and price competitiveness. The antioxidant activity of lignin depends on its structural properties, and they accordingly have synergy with natural antioxidants. Based on the structural characteristics, the antioxidant activity of ethanol organosolv lignin (EOL) and synergy with myricetin were investigated. The phenolic-OH content was a predominant factor in the antioxidant activity of EOL, and EOL-H with a higher phenolic-OH content and lower IC50 value (0.17 mg/mL) covered a wide synergy range of 1:32–2:1 (EOL:myricetin). The synergistic effect was verified by comparing predicted and actual values based on ESR analysis, and the phenolic-OH ratio (>0.4) of myricetin and EOL for the synergy was suggested. In this respect, the results highlight the potential of lignin with high phenolic-OH content as a substitute for commercial antioxidants with superior activity and broad synergy ranges.