Lignin extraction from lignocellulosic biomass and its valorization to therapeutic phenolic compounds

Lignocellulosic biomass is a sustainable alternative to finite petroleum resources, with lignin emerging as a major component of biomass for producing circular economy products. Maximizing extraction and valorization of lignin to platform chemicals, biofuels, and bioactive compounds is crucial. Unlocking lignin's full potential lies in exploring the therapeutic properties of lignin-derived phenolics, which can definitely boost the economic viability of integrated biorefineries. This review provides a broad vision of lignin valorization stages, covering various techniques of its extraction from lignocellulosic biomass with high yield and purity and its further depolymerization to phenolics. Therapeutic potential of lignin-derived phenols as antioxidants, antimicrobials, anti-inflammatory, and anticancer agents is comprehensively discussed. Lignin, with high phenolic hydroxyl content up to 97% purity, can be extracted using deep eutectic solvents (DES) and organosolv processes. Oxidative and reductive catalytic depolymerization methods efficiently break down lignin into valuable phenolic compounds like alkyl phenolics and vanillin, even at mild temperatures, making them a preferred choice for lignin valorization. Potential of lignin derived phenolics as versatile bioactive compounds with health promoting benefits is highlighted. Phenolics such as vanillin, ferulic acid, and syringic acid have demonstrated the ability to modulate cellular pathways involved in the pathogenesis of diseases like cancer and diabetes. The interplay between high purity lignin extraction and therapeutic potential of lignin-derived phenolics unveils a new frontier in sustainable healthcare solutions.