Review on lignin modifications toward natural UV protection ingredient for lignin-based sunscreens

Abstract

Lignin is a natural UV-blocking material; it exhibits excellent UV absorption ability owing to its aromatic structure and the presence of numerous phenolic, ketone, and intramolecular hydrogen bonds. Recently, the utilization of lignin as a replacement for conventional mineral and synthetic UV protection ingredients in sunscreens has been recognized as an attractive and promising concept from the viewpoint of renewable and sustainable manufacturing of lignin-based products. Despite its significant UV-blocking potential, the intrinsic dark color of lignin results in the unavoidable dark color of lignin-based sunscreens, which significantly limits its wide application. Therefore, the present review focuses on providing a comprehensive insight into lignin-based sunscreens. The positive effects of the sunblocking ability of lignin and the drawbacks associated with lignin-based sunscreens, from the viewpoint of cosmetic appearance, were investigated in detail. To address the bottlenecks of lignin-based sunscreens, several methods, including fractionation and modification on the chemical structure, morphology, and particle size of lignin, were subsequently developed. In addition, future perspectives of lignin-inspired sunscreen production were discussed to suggest promising approaches for a facile and green manufacturing of natural sunscreens from lignin.