Antioxidant Activity of Hydrogen-Reduced Alkali Lignin Prepared Using Palladium/Carbon (Pd/C) as Catalyst

In this study,commercial and laboratory-prepared Pd/carbon catalysts were used for the reduction of industrial alkali lignin by hydrogen under high pressure conditions in order to increase lignin activity.The chemical composition and antioxidant activity of alkali lignin and its reduced products were analyzed.The contents of alcohol hydroxyl groups and phenolic hydroxyl groups in commercial Pd/carbon activated alkali lignin were 5.01% and 3.64%,respectively,compared to 5.35% and 3.82% for laboratory-prepared Pd/carbon activated alkali lignin.Thus,the laboratory-prepared Pd/carbon has better catalysis performance than the commercial Pd/carbon.Both alkali lignin and its reduced products had strong radical scavenging activity against DPPH and hydroxyl radicals at a concentration ranging from 0.025 to 0.6 mg/mL in a concentration-dependent manner.The maximum scavenging rates of commercial Pd/carbon activated alkali lignin and laboratory-prepared Pd/carbon activated alkali lignin were 80.91% and 82.43% for DPPH free radical and 23.12% and 26.21% for hydroxyl free radical,respectively.