Lignin: a nature-inspired sun blocker for broad-spectrum sunscreens†
We report the evaluation of lignin for the development of high-performance broad-spectrum sunscreens. Lignin is added into several commercial sunscreen products. Significant enhancements in ultraviolet (UV) absorbance are observed. The results show that the sunscreen effect of sun protection factor (SPF) 15 could reach that of SPF 30 with the addition of 2 wt% lignin. Adding 10 wt% lignin makes SPF 15 outperform SPF 50. It is also interesting to find that the sunscreen performance improves with UV-radiation time. After 2 h of UV radiation, the UV absorbance of the 10 wt% lignin SPF 15 lotion increases dramatically. This has been attributed to certain synergistic effects between lignin and other sunscreen actives in the lotions, as well as the antioxidant property of lignin. This nature-inspired lignin system may provide a green alternative to replace some synthetic sunscreen actives.