Ultrasound-assisted deep eutectic solvent-mediated nano-lignin isolation from Prunus persica endocarp for broad-spectrum sunscreen application

Abstract

Chemical sunscreens are widely used nowadays because of their capacity to protect the skin from ultraviolet radiation. However, commercial chemical sunscreens provide limited sun protection factor and broad-spectrum protection, typically ultraviolet A₁ (UVA₁), which covers wavelengths from 340 to 400 nm. Thus, in this study, ultrasound-assisted DES-mediated nano-lignin isolation was performed to investigate the potential of nano-lignin to improve the sun protection factor (SPF) value and broaden the UV absorption spectrum, thereby lowering transmittance in the wavelength range of 290–400 nm. As a result, nano-lignin was mixed with an SPF 27 commercial sunscreen (CSS), and the SPF value and broad-spectrum coverage were evaluated. The obtained results showed substantial improvements in the SPF value and broadened the UV absorption spectrum, which corresponded with the amount of nano-lignin incorporated. At 1 wt% of nano-lignin, the SPF value improved from control SPF 27 to SPF 30.65. Accordingly, increasing the amount of nano-lignin concentration to 5 wt% and 10 wt% increased the SPF values significantly to 36.75 and 48.59, respectively, under similar conditions. Correspondingly, the UV absorption spectra of the formulations were analyzed to evaluate the changes in the absorbance range relevant to UVA₁, and a promising result was obtained with10 wt% of nano-lignin addition. The improvements in the SPF value and spectrum range could be attributed to the synergistic effects of the aromatic functional groups in nano-lignin and chemical sunscreen actives in CSS. Thus, nano-lignin can be considered a possible alternative to chemical sunscreen actives.