Long-time exposure to the sun's ultraviolet (UV) radiation is harmful and causes various skin problems. Natural sun blockers have been drawing considerable attention recently. Even though lignin, an abundant aromatic polymer from plants, is a natural UV screening agent, its unfavorable dark color hinders its high value-added applications in sunscreens and cosmetics. In this study, we separate lignin under mild conditions (at room temperature with neutral solvents) in order to prevent darkening occurring during delignification and apply the resultant lignin as a natural sunscreen ingredient for the first time. Lignins isolated from Miscanthus sacchariflorus (MWL-M) and from Pinus densiflora (MWL-P) are compared with organosolv lignin (OL), which showed the best sunscreen performance, in color and UV protection. MWLs separated under mild conditions were light in color unlike conventional lignins extracted under harsh conditions. UV absorption of light-colored MWL-M was revealed to be as high as dark-colored OL. MWLs also showed synergistic effects with a commercial sunscreen; exposure of the MWL-added sunscreen to UVA radiation greatly enhanced the sun protection factor (SPF) value of the sunscreen.
Keywords: Lignin color; Milled wood lignin; UV absorption.
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