UV-absorption Capacity of Selected Crude and Functionalized Lignin for Use in Sunscreens

Abstract

The most commonly used commercial sunscreen agents are aromatic compounds oxybenzone and octinoxate, as they offer a wide range of protection in the UV spectrum. However, oxybenzone has the highest rate of skin irritation, while octinoxate has poor photostability. Oxybenzone is also a genotoxicant and skeletal endocrine disruptor to corals. Appropriate, less toxic and preferentially biorenewable alternatives should be recommended. Lignin, an abundant byproduct of pulp and biorefinery industries, is expected to be an effective replacement for oxybenzone and octinoxate due to its aromatic structure, which, in synergy with a wide variety of functional groups, produces the absorption of energy in the entire UV region. Additionally, lignin is a biocompatible polyphenolic with a strong radical quenching ability, i.e., anti-oxidizing potential. Therefore, it is a promising replacement for synthetic chemicals in cosmetics, sunscreen, and other applications. The UV absorption analysis of selected crude and functionalized lignin samples was conducted, and the results were compared to those of commercially used UV-absorption agents—oxybenzone and octinoxate. The results showed that the total absorption capacity of the lignin samples is lower by 6.4x and 16.3x compared to oxybenzone and octinoxate, respectively; however, it covers a wide absorption range in the UV spectrum. The lignin samples also showed good photostability and color stability, in contrast to the observed yellowing of octinoxate after 3 hours of exposure to sunlight. The UV spectra of some of the lignin samples indicate that their UV absorption capacity was enhanced by as much as 13.31% after exposure to sunlight.