Antioxidant profiling by two-dimensional chromatography with post-column ABTS: example of lignin

Area of Science:

• Biochemistry
• Polymer Chemistry
• Natural Products Chemistry

Background:

• Lignin is a renewable resource gaining attention as a sustainable alternative to fossil-based antioxidants.
• Understanding lignin's antioxidant properties is crucial for its application in various industries.
• Conventional methods for assessing antioxidant activity often lack the resolution to analyze complex lignin structures.

Purpose of the Study:

• To characterize the antioxidant activity of softwood Kraft lignin at a molecular level.
• To correlate specific molecular weight fractions of lignin with their radical scavenging capacity.
• To guide the selection of lignin fractions for optimal antioxidant applications.

Main Methods:

• Two-dimensional liquid chromatography (2D-LC) combining size-exclusion and reversed-phase chromatography.
• Post-column radical scavenging assay using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS).
• Profiling antioxidant activity across monomeric, oligomeric, and polymeric lignin fractions.

Main Results:

• Identified four guaiacyl-type monomeric compounds in softwood Kraft lignin.
• Guaiacol demonstrated the highest specific radical scavenging activity among monomers; vanillin showed minimal activity.
• Antioxidant activity was observed in oligomeric and polymeric fractions, with higher specific activity in lower molecular weight polymeric lignin.

Conclusions:

• The study provides a detailed structure-property relationship of lignin's antioxidant activity.
• 2D-LC coupled with a radical scavenging assay offers superior resolution compared to bulk methods.
• Findings facilitate targeted selection of lignin fractions for enhanced antioxidant applications.