HPLC-quantified monosaccharide profiles guide FTIR/13C NMR-correlated bioactivities in species-specific seaweed polysaccharides for precision cosmeceuticals

Seaweed polysaccharides exhibit skin-protective properties, yet species-specific structural determinants of their functionalities remain unexplored. Here, polysaccharides from Sargassum, Ulva and Laminaria digitata were extracted via response surface methodology (RSM)-optimized protocols, quantified by HPLC (monosaccharide composition, sulfate content) and characterized by Fourier transform infrared spectroscopy (FTIR), 13 C nuclear magnetic resonance ( 13 C NMR) and gel permeation chromatography (GPC). Functional validation across cell (RAW264.7 macrophages, HaCat and chorioallantoic membrane assays), ex vivo (antioxidant capacity, UV absorption, hygroscopicity) and in vivo models (rat auricle edema, skin irritation) confirms both efficacy and safety for cosmeceutical use. Sargassum contains a dominant 599.87-kDa fucoidan with diagnostic NMR signals at δ15.05 ppm (C6-CH₃ of L-fucose) and δ100.25–101.87 ppm (anomeric C1), alongside FTIR bands for sulfate (1250 cm −1 ), fucose-specific C–O–S bending (840 cm −1 ) and hydration-associated O H bending (1650 cm −1 ), correlating with its antioxidant activity (62.67 ± 5.22 % hemolysis inhibition). Ulva comprises a 22.21-kDa ulvan exhibiting NMR peaks at δ107.05 ppm (C1 of α-L-rhamnose-3-sulfate) and δ16.86 ppm (C6-CH₃ of rhamnose), plus FTIR signatures of sulfate (1240 cm −1 ), broad O H stretching (3400 cm −1 ) and rhamnose C H deformation (890 cm −1 ), enabling hygroscopic hydrogel formation and UV shielding (61.31 ± 0.78 %). Laminaria digitata features a 180.29-kDa alginate with NMR signals at δ176.89 ppm (carboxyl carbon) and δ102.78–103.54 ppm (anomeric carbons of mannuronic and guluronic acid residues), and FTIR bands for carboxyl (1720 cm −1 ) and bound water (1640 cm −1 ), driving moisturization (64.81 ± 10.01 %) and hyaluronidase inhibition (27.26 ± 2.03 %) . All polysaccharides demonstrated zero irritation and excellent biocompatibility, thus supporting species-specific cosmetic applications: Sargassum for antioxidant-focused formulations, Ulva for UV-protective products and Laminaria digitata for hydration and anti-inflammatory-oriented cosmeceuticals.