Lignin as a Natural Antioxidant: Chemistry and Applications

The growing interest in renewable and natural antioxidants has positioned lignin as one of the most significant bioresources for sustainable applications. Lignin, a polyphenolic biomolecule and a major by-product of chemical pulping and biorefinery processes, is abundant and widely accessible. Recent advancements in lignin modification, fractionation, and innovative biorefinery techniques have expanded its potential applications, particularly as a natural antioxidant. This review explores the underlying chemistry of lignin’s antioxidant activities, from model compounds to technical lignin resources, and examines its current applications. Additionally, we highlight the influence of lignin’s chemical structure and functional groups on its antioxidant efficacy, emphasizing its promising role in the development of practical and sustainable solutions.