Polysaccharide precipitation enhances the preventive effects of ultrasonicated Undaria pinnatifida (Laminariales, Phaeophyta) sporophyll extract against acute skin damage and oxidative stress

Although Undaria pinnatifida sporophyll is rich in beneficial components such as polysaccharides, proteins, and phy-tochemicals, its inaccessible structure limits its usability. To overcome this limitation, we ultrasonically extracted U. pin-natifida sporophyll extract (UPE) under optimized conditions (20 kHz, 1,080 W, 30°C) for 8 h and used gradient ethanol precipitation to isolate the UPE fractions (UEF). The yield, composition, and molecular weight of the UEFs changed as fractionation progressed, and the galactose and fucose content increased. Interestingly, the sulfate polysaccharide con-tents were not related to the fractionation process: UEF3 showed the highest content among the fractions (33.89 ± 0.05%). UEFs had no cytotoxic effects on HaCaT, RAW 264.7, or BEAS-2B cells, and UEF3 prevented ultraviolet B (UVB)-induced cyclooxygenase-2 (COX-2) expression by regulating the ERK kinase pathway. The oral administration of UEF3 prevented epidermal thickening and COX-2 overexpression in UVB-exposed mice. UEF3 also alleviated oxidative stress by reducing reactive oxygen species levels via the activation of the HO-1 / NRF2 signaling pathway. This indicates that polysaccharide precipitation fractionation enhances efficacy by isolating the functional components. In conclusion, fractional processing using ultrasonic-assisted extracts can be an effective approach for developing nutraceutical materials for human health.