Extraction, isolation, purification, structural characterization, and antitumor activity of polysaccharides from safflower seed residues

Polysaccharides from safflower seed residue (SSRPs) were extracted using hot water (100°C, 2 h, liquid-to-solid ratio 10:1), ethanol-precipitated, deproteinized by the Sevag method, and purified sequentially by DEAE-52 cellulose and Sephadex G-100 chromatography. Three fractions, SSRP1–SSRP3, were obtained with yields of 10.0 ± 0.88%, 8.5 ± 0.38%, and 6.33 ± 0.13% and purities of 90.91 ± 1.07%, 88.90 ± 0.97%, and 77.78 ± 0.59%, respectively. Chemical analysis showed total sugar contents of 45.07 ± 0.26%, 32.53 ± 0.48%, and 20.99 ± 0.39%, with uronic acid levels of 9.49 ± 0.42%, 7.79 ± 0.60%, and 6.67 ± 0.26%. Zeta potentials ranged from –16.4 to –32.9 mV, suggesting strong colloidal stability. The molecular weights were 0.707, 2.033, and 3.942 kDa, and monosaccharide analysis identified fructose, glucose, and galactose as the main components. FT-IR confirmed functional groups, while 2D NMR (HSQC, HMBC, COSY) revealed backbones of 4-linked AnGalp 2-sulfate, α-1-Galp, and α-2,3-Fucp residues. SEM imaging showed porous and lamellar morphologies. Antitumor activity was assessed by CCK-8 assay on HepG2 cells, showing dose-dependent inhibition with IC 50 values of 249 ± 12.3 µg/mL (SSRP1), 276.14 ± 6.22 µg/mL (SSRP2), and 490.91 ± 8.17 µg/mL (SSRP3). These findings demonstrate that SSRPs possess distinct structural features and significant antitumor activity, highlighting their potential as natural anticancer agents and functional food ingredients.