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Proceedings of the 90th JSCM Anniversary Conference
J. Jpn. Soc. Colour Mater., 91〔3〕，103–105（2018）

Preparation of Composites of Citrus Flavonoids and Various Porous Silica Materials andtheir Performance as Ultraviolet Absorbers for Sunscreens
Piyarattanawat Wiwanthanee＊ and Masashi Shibata＊,†＊ School of Bioscience and Biotechnology, Tokyo University of Technology, 1404-1 Katakura-machi, Hachioji, Tokyo 192-0982, Japan†Corresponding Author, E-mail: mshibata@stf.teu.ac.jp(Received December 1, 2017; Accepted January 22, 2018)
Abstract
Flavonoids from the citrus fruit shekwasha were adsorbed on two types of porous silica materials, mesoporous silica and amorphous silica
gel, in order to improve the ultraviolet A (UVA) absorption capacity and prevent the penetration of flavonoids into the skin. Mesoporous silica
showed a higher adsorptive capacity of flavonoids than the amorphous silica gel, owing to its high surface area and uniform mesoporousstructure. Both the composites (in powdered forms) exhibited UVA absorption, but the silica gel composite also showed absorption in thevisible range, making it less suitable as a UVA absorber. The oil dispersions of the mesoporous silica composites in the form of thin films
also absorbed UVA effectively, indicating that the mesoporous silica composite with the shekwasha flavonoids can be used as a new UVA
absorber in skin cosmetics.
Key-words: Citrus depressa, Flavonoids, Silica gel, MCM-41 mesoporous silica, UV-vis absorbance

1．Introduction
Ultraviolet (UV) radiation can be classified on the basisof wavelength as UVA (320-400 nm), UVB (280-320 nm)
and UVC (100-280 nm). Among these, UVA is responsible
for causing skin tanning and premature skin aging such as
wrinkles and dark spots. Hence, various UVA protective agentsare used in daily use cosmetics such as lotions and creams.
Ultraviolet protective agents (sunscreen materials) for
cosmetics can be organic or inorganic. Inorganic materials
like titanium oxide and zinc oxide are known to be generally
stable and cause less skin problems. However, they are nottransparent (too white) and tend to cause a rough, ‘powdery’feeling when applied on the skin, making them less desirable
for use as UVA protection cosmetics.
Organic materials such as avobenzone, octylcrylene, andoctinoxate are transparent and oil soluble, but are likely tocause skin irritation as they can penetrate the skin1).
Flavonoids are natural organic compounds present inmany kinds of fruits. The flavonoids derived from the citrus
fruit shekwasha (Citrus depressa) contain polymethoxylated
flavones ( PMFs ) , mainly nobiletin and tangeretin(Fig. 1), which are recognized for their antioxidant andanti-inflammatory properties. In addition, their solutions
effectively absorb UVA and are also transparent (colorless),
thereby making them attractive natural UVA protection agents.
However, reports indicate that they can cause skin irritation2).
Porous silica materials such as mesoporous silica (MPS),
zeolites, and amorphous silica gel are widely used to stabilizeorganic molecules by adsorbing them into their pores.
Among these, MPS composites are well-known due to theirhigh surface area (>1000 m2/g), and well-ordered and tunableuniform pore sizes (1-30 nm)3) which are appropriate for
fitting the molecular structures of PMFs.
In this study, one such popular mesoporous silica ofthe type MCM-41 was prepared by the hydrothermal
synthesis method and used to adsorb PMFs from shekwasha
flavonoids. The obtained PMF-MPS composites ( withdifferent amounts of adsorbed PMFs) were then investigatedas UVA protective agents, by comparing their adsorption
efficiency and UV-vis absorption performance with thatof amorphous silica gel based PMF composites. In order
to be ideal UVA protective agents for use in cosmetics, thePMFs must first be highly adsorbed and uniformly dispersed
within the pores of the MPS. They must also absorb UVA
effectively, without absorbing visible light (therefore becolorless) in their composite powder forms. In addition tothis, the composites must exhibit effective UVA absorption
performance even when dispersed in thin oil-based films,
similar to actual application on the skin.

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OOOOOOOOOOOOOFig. 1 Chemical structure of PMFs.

© 2018 Journal of the Japan Society of Colour Material