Tannic acid-assisted fractionation of lignin with multifunctional properties for sunscreen formulations

Lignin contains aromatic rings, phenolic hydroxyl, and methoxy groups that confer promising potential for sunscreen applications. However, traditional extraction methods often lead to structural condensation, thus limiting the functional utilization of lignin. Herein, we propose a strategy for simultaneous lignin extraction and in-situ modification using tannic acid (TA) as both a functionalizing agent and a phenolic modifier. This approach enables efficient lignin isolation under mild conditions, while preserving reactive sites and enhancing multifunctional performance. Under optimized conditions (100 °C, 30 min), the pretreatment achieved a delignification efficiency of 89.1 %. The resulting TA-modified lignin (TA-Lig) exhibited excellent UV-blocking performance, antioxidant activity, tyrosinase inhibition, and favorable biocompatibility. Notably, incorporating 5 wt% TA-Lig into a commercial sunscreen (SPF 15) markedly enhanced the SPF to 145.3. This work demonstrates a sustainable extraction-modification strategy that yields multifunctional bio-based ingredients with strong potential for cosmetic applications.