Anti-Melanogenic Effects of a Polysaccharide Isolated from Undaria pinnatifida Sporophyll Extracts

<i>Undaria pinnatifida</i> is a temperate brown alga known to exert free radical-scavenging and anti-inflammatory effects. In this study, we investigated the skin-whitening effects of <i>U. pinnatifida</i> sporophyll extracts (UPEs) in α-melanocyte-stimulating hormone (α-MSH)-stimulated B16F10 melanoma cells. The crude polysaccharide fraction (UPF) was obtained via ethanol precipitation. Four polysaccharide fractions (UPF1-4) were isolated and purified using ion-exchange column chromatography, and their anti-melanogenic activity was evaluated. UPF3 exhibited the highest anti-melanogenic activity, showing the highest sulfate (39.79%), fucose (143 μg/mg), and galactose (208 μg/mg) contents. UPF3 significantly inhibited intracellular tyrosinase activity in B16F10 cells. We also evaluated the melanogenic signaling pathway to determine the mechanism of action of UPF3 in melanongenesis. UPF3 reduced the expression of tyrosinase-related protein-1 (TRP-1), tyrosinase-related protein-2 (TRP-2), and tyrosinase, which play important roles in melanin production. Therefore, UPF3 has high potential for use in skin-whitening functional pharmaceuticals and cosmetics.