108

Original Research Paper

J. Jpn. Soc. Colour Mater., 96〔3〕，108–112（2023）

Enhancement of the Adsorbed Amount of Ferulic Acid on Mesoporous Silicafor Use as an Ultraviolet Radiation Absorber in Cosmetics
Sara Saijo＊, Masashi Shibata＊ and Chihiro Izawa＊,†＊School of Bioscience and Biotechnology, Tokyo University of Technology, 1404-1 Katakura-machi, Hachioji, Tokyo 192-0982, Japan†Corresponding Author, E-mail: izawachr@stf.teu.ac.jp(Received December 15, 2022; Accepted February 8, 2023 )Abstract
To increase the amount of ferulic acid adsorbed on a ferulic acid-silica composite, which is expected to be applied as a UV-protection
material, a method for preparing the composite by using an anti-solvent precipitation method was investigated. Mesoporous silica wasdispersed in a 50% ethanol solution of ferulic acid, and water was added as the poor solvent; the resultant adsorption amount was fivetimes higher with water added. The diffuse reflectance spectrum of the prepared ferulic acid-mesoporous silica composite only showed theabsorption of ultraviolet light and no absorption of visible light. This confirmed that ferulic acid was adsorbed into the pores of the powder,and not on its surface.
Key-words: Ferulic acid, MCM-41 mesoporous silica, Pore adsorption, Compositing, UV absorption

1．Introduction
Compositing organic materials, such as plant pigmentswith inorganic carriers, can increase the dispersion, stability,
and leaching resistance of pigments into solvents. Layered
clay minerals are commonly used as inorganic carriers 1,2 ).
Conversely, mesoporous silica, porous silica with uniform
nano-sized pores, has a pore size close to the molecular sizeof plant pigments and a high surface area (>1,000 m 2 /g).
Therefore, porous silica is expected to adsorb a larger
number of pigments with high stability compared to clay
minerals. We have previously reported that the adsorptionof anthocyanin dyes into the pores of MCM-41 mesoporous
silica can enhance their stability against light and heat 3 ).
Polymethoxyflavonoids, a type of flavonoid-like
anthocyanin pigment, are polyphenols found in the citrus
fruit sheckwasa. Although polymethoxyflavonoids arecolorless, they have UV-absorption ability. Therefore, theuse of polymethoxyflavonoids as UV-absorbing powders has
been investigated by adsorbing and compositing them into
the pores of mesoporous silica 4 ).
Ferulic acid, a derivative of silicic acid found in rice
and wheat seeds, is a plant-derived ultraviolet ( UV )absorber. The structural formula of ferulic acid is shown in

Fig. 1. Like polymethoxyflavonoids, it is also desirable tocomposite ferulic acid with mesoporous silica. However,compositing it in the same way as anthocyanin pigments andpolymethoxyflavonoids is presumed to be difficult because it
is insoluble in water.
In this study, we investigated an anti-solvent precipitation
method, which is an adsorption method utilizing solubility
differences among solvent species 5 ), to adsorb ferulic
acid, which is insoluble in water but soluble in ethanol, in
the pores of mesoporous silica 6 ). In this method, a highconcentration solution was prepared using a good solvent,the carrier was dispersed in the solution, and the solubilityof the solute was decreased by adding a poor solvent. Thusfar, adsorption on carbon nanotubes using the solubility
difference of ofloxacin 7 ), and on silica using the solubility
difference of carbofuran 8 ), have been reported.
In this study, ferulic acid composites were prepared by theanti-solvent precipitation method using mesoporous silica as
the carrier, an aqueous ethanol solution ( 50% concentration)
as the good solvent, and water as the poor solvent. The
adsorption behavior of ferulic acid into the mesoporous
silica pores, and the UV absorption capacity of the resulting
ferulic acid composites, were compared with those ofpolymethoxyflavonoid composites.

2．Materials and Methods

Fig. 1 Structural formula of ferulic acid.

© 2023 Journal of the Japan Society of Colour Material

Ethanol solutions of various concentrations ( 50 mL) wereprepared using ultrapure water and 99.5% ethanol (FUJIFILM
Wako Pure Chemical Co., Ltd.), and 5 g of ferulic acid
(Tokyo Kasei Kogyo Co., Ltd.) was added. Next, the solution－14－