Introduction
Rice is a grain cultivated in many countries worldwide, particularly in
East and Southeast Asia. Rice bran, a non-edible part of rice, accounts
for approximately 10% of its weight and is known to contain various
functional ingredients (Ghosh, 2007). Phytosterols and their esters are
among the functional components of rice bran. Phytosterols are used as
food additives, such as natural emulsifiers and processing aids, and are
widely found in pharmaceuticals and cosmetics. Their biological
functions have been studied in medicine and food, and one of their
effects is the suppression of blood cholesterol (Pollak, 1953, Joneset al. , 2000, Vissers et al ., 2000). Phytosterols
are also known to exert anti-inflammatory effects in cosmetics (Loizouet al. , 2009). However, the biological functions of the ester
forms of phytosterols have not been elucidated.
Phytosterols differ depending on the plant species. Rice bran contains
large amounts of the plant sterols β-sitosterol and campesterol, as well
as the triterpene alcohols cycloartenol and 24-methylenecycloartenol
(Akihisa et al. , 1996, Shimotoyodome et al ., 2017). We
developed a method for producing RSE from by-products of the rice bran
oil refining process. RSE is an oil rich in esters of phytosterols,
triterpene alcohols, and fatty acids that has been confirmed to have
high water-retention and emollient effects(Janeš et al. , 2018).
However, there are few examples of biological verification of the
cosmetic effects of phytosterols using cultured skin cells. Therefore,
in this study, we examined whether phytosterol esters derived from rice
bran have effects on the skin.