Fucoidan Fractionated from Sargassum coreanum via Step-Gradient Ethanol Precipitation Indicate Promising UVB-Protective Effects in Human Keratinocytes

Fucoidans exhibit a wide range of bioactivities and receive significant attention in functional food and cosmetic research. Industrial applications of fucoidan are limited partially due to high extraction and purification costs. The present study implements an enzyme-assisted extraction and step-gradient ethanol precipitation for fractionating fucoidan from Sargassum coreanum based on its charge and molecular weight and evaluation of ultraviolet B (UVB) protective effects in human keratinocytes (HaCaT). The fucoidan fraction SCOC4 indicated higher fucose and sulfate contents with Fourier-transform infrared and ¹H NMR spectral patterns resembling fucoidans. SCOC4 dose-dependently abated UVB-induced keratinocyte damage via suppressing intracellular reactive oxygen species, apoptotic body formation, DNA damage via suppressing mitochondria-mediated apoptosis. UVB-protective effects of SCOC4 were further attributable to the augmentation of nuclear factor erythroid 2-related factor 2 mediated cellular antioxidant defense enzymes. Step-gradient ethanol precipitation was a convenient approach of fractionating fucoidans based on molecular weight and charge (depend on the degree of sulfation). Further evaluation of seasonal variations, biocompatibility parameters, efficacy, and shelf life may widen the use of S. coreanum fucoidans in developing UVB-protective cosmetics and functional foods.