posted on 2023-12-01, 18:43authored byJunyu Chen, Junfei Tian, Shaokai Zhang, Azadeh Nilghaz, Yunbo Xie, Xiaofang Wan
Light-color and UV-shielding properties were both critical
factors
of lignin-based sunscreens. Lignin’s conjugated structure provides
effective UV-shielding characteristics that also impart coloration,
making it challenging to achieve a balance between the two. The color
requirements of sunscreens often require a compromise in the UV-shielding
properties of lignin. To resolve this issue, a sustainable and efficient
method was proposed by utilizing biocompatible pyruvic acid to fractionate
the Camellia oleifera shell, resulting
in the extraction of a light-colored lignin with exceptional UV absorption
at 290–400 nm. Incorporating 1% lignin into sunscreens led
to a significant increase in the sun protection factor (SPF) of the
resulting product (from 18.19 and 32.72 to 29.79 and 49.52, respectively),
with no staining on skin. The characteristic of the lignin structure
demonstrates that the light-colored lignin can be largely attributed
to the G group lignin swiftly dissolving in pyruvic acid without notable
condensation. The enhanced UV-shielding properties of lignin arise
from the cleavage of the β-O-4 bond, resulting in the production
of more phenolic hydroxyl groups and the esterification of pyruvic
acid with the hydroxyl groups of the side chains.