Molecular Insights into Lignin Bioactivity: From Structural Architecture to Sustainable Food Industry Applications

This review explores the biological properties and application potential of native, technical, and modified lignins, with a focus on their antioxidant, antimicrobial, and anti-inflammatory activities. Native lignin generally preserves more of its original phenolic architecture and thus shows stronger intrinsic biological activity. This is likely due to its more homogeneous structure, which makes its physicochemical behavior more predictable compared with highly processed technical lignins. Among technical lignins, organosolv and soda lignin appear the most promising due to their sulfur-free nature, lower condensation, and higher reactivity. At the monomer level, catechol-type phenolics show the highest antioxidant potential, while vanillin remains the most attractive lignin-derived monomer because it combines bioactivity with direct application potential in food, pharmaceutical, and cosmetic systems. Comparison of modification strategies indicates that phenolic grafting, esterification, and carboxylation are more practical for scale-up than complex multistep polymer grafting. In particular, gallic acid grafting produced some of the strongest results, including near-complete 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging, 98.7% 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical inhibition, and a fourfold increase in phenolic hydroxyl content, whereas other modified lignins also showed improved antimicrobial and anti-inflammatory effects. Overall, mild and green lignin modification, especially with food-safe phenolic compounds, appears to be the most promising strategy for future food and human health applications.