PROBLEM TO BE SOLVED: To provide a manufacturing method for a sialic acid derivative exhibiting a skin epithelial cell-activating action.SOLUTION: The sialic acid derivative includes sialic acid and polyphenol. The sialic acid derivative is featured in that it is formed by a transesterification reaction caused by fermentation. The manufacturing method comprises a step of alkali-reducing fermentation liquid obtained by adding bacillus natto to fig fruits, gold powder and soybean powder and fermenting the mixture. The obtained sialic acid derivative exhibits more excellent effects than EGF and is applied as cosmetics, food preparations and medicines. In particular, it is applied to cosmetics that enhance skin barrier and exhibits excellent water retention and elasticity of the skin.
