Isolation, Chemical Structure, and Antagonistic Activity Against Galectin‐1 of Water‐Soluble Polysaccharides From <i>Plantago asiatica</i>

<i>Plantago asiatica</i> has been utilized as a dietary supplement in health foods and for medicinal purposes, enjoying a long-standing acceptance throughout history. A neutral polysaccharide fraction (WPA-N) and three acidic polysaccharide fractions (WPA-1, WPA-2, and WPA-3) prepared from <i>Plantago asiatica</i> by water extraction and DEAE-cellulose were tested for their chemical structures and inhibitory effects on galectin-1-mediated bioactivity. The results showed that WPA-N was composed of Glc and Gal residues, while WPA-1, WPA-2, and WPA-3 were mainly constituted by GalA, Gal, Ara, Rha, as well as some other monosaccharide residues, with the molecular weights ranging from 68.7 kDa to 168.2 kDa. Galectin-1 has been identified as a mediator in the multi-step process of tumor cell aggregation, migration, and invasion, as well as in tumor-induced angiogenesis, including in cervical cancer. Except for WPA-N, three acidic fractions could inhibit galectin-1-mediated hemagglutination and also could inhibit the fluorescence intensity of galectin-1 protein, and WPA-3 showed the strongest activity. Besides, anti-cancer experiments showed three acidic fractions could inhibit the growth and migration of cervical cancer ME180 cells, and WPA-3 inhibited the proliferation and migration activity of ME180 better than others. Biolayer interferometry analysis found that WPA-3 had a very strong binding ability to galectin-1 protein, with a <i>KD</i> value of 26.8 nM. WPA-3 contained rhamnogalacturonan-I mainchain with branched galactan, arabinan, and arabinogalactans-II side chains and some homogalacturonan domain. These findings indicated the potential applications in functional food fields of <i>Plantago asiatica</i> polysaccharides.