Light-colored, low-condensed lignin via ultrasound- and alkali-assisted ethanol extraction for high-performance sunscreens.

The efficient and high-value utilization of lignin is crucial for advancing sustainable biorefining technologies. Conventional lignin separation methods often lead to the cleavage of β-O-4 linkages, resulting in dark-colored, highly condensed lignin with limited applicability in downstream industries. To overcome this limitation, an ultrasonic- and alkali-assisted ethanol extraction (UASE80) method was developed that enables efficient isolation of light-colored, low-condensed, and highly reactive lignin from poplar wood at ambient temperature. The extracted lignin retains a significant portion of β-O-4 bonds (53.5/100Ar), representing 90.3 % of the raw content, with a yield of 45.17 % and a purity of 99.9 %. After nanotechnology processing, the resulting lignin nanoparticles exhibit excellent UV-shielding performance. With only 10 wt% addition, they increase the Sun Protection Factor (SPF) of a pure cream from 1.04 to 20.13, while maintaining desirable sensory characteristics and compatibility with natural skin tones. This work offers a green and efficient strategy for producing high-quality, functionally enriched lignin, underscoring its promising potential for high-value applications in cosmetics and functional materials.