Physicochemical Properties and Biological Activities of Quinoa Polysaccharides

Quinoa, known as the "golden grain" for its high nutritional value, is a significant source of essential nutrients, including proteins, minerals, vitamins, polyphenols, phytosterols, and flavonoids. However, the biological functions of quinoa polysaccharides remain understudied. In this research, two crude quinoa polysaccharides extracts (Q-40 and Q-60) were obtained extracting by 40% and 60% alcohol. The purity of Q-40 and Q-60 was 58.29% and 62.15%, with protein contents of 8.27% and 9.60%, respectively. Monosaccharide analysis revealed that Q-40 contained glucose (Glc), galacturonic acid (GalA), and arabinose (Ara) in a molar ratio of 0.967:0.027:0.006. Q-60 was composed of xylose (xyl), arabinose (Ara), galactose, and galacturonic acid (GalA) with a molar ratio of 0.889:0.036:0.034:0.020. The average molecular weight of Q-40 ranged from 47484 to 626488 Da, while Q-60 showed a range of 10025 to 47990 Da. Rheological experiments showed that Q-40 exhibited higher viscosity, while Q-60 demonstrated more elastic properties. Remarkably, Q-60 showed potent antioxidant abilities, with scavenging rates of 98.49% for DPPH and 57.5% for ABTS. Antibacterial experiments using the microdilution method revealed that Q-40 inhibited the growth of Methicillin-resistant Staphylococcus aureus (MRSA) and E. coli, while Q-60 specifically inhibited MRSA. At lower concentrations, both polysaccharides inhibited MDA cell proliferation, but at higher concentrations, they promoted proliferation. Similar proliferation-promoting effects were observed in HepG2 cells. The research provides important information in application of quinoa in food and functional food industries.