Boronate affinity-mediated magnetic solid phase extraction and bioactivities of polysaccharides from beverage plants

Polysaccharides are of great significance in food production,but their isolation highly relies on multi-staged liquid-liquid extraction.In this study,a boronate affinity-mediated magnetic solid phase extraction(BA-MSPE)method was initiated for the effortless and efficient extraction of polysaccharides using boronic acid-grafted magnetic nanospheres(MNPs@B(OH)_(2))as extractants.MNPs@B(OH)_(2)showed fine class selectivity toward cis-diol containing compounds at weak alkaline condition(pH 7.5~8.5)and higher binding capacity than that of MNPs without boronic acid functionalization.Fast binding dynamics with a binding equilibrium within 10 min,stronger affinity toward polysaccharides(Kd as low as 10^(−3)~10^(−6)M level)than that of small molecular cis-diol compounds(Kd in the range of 10^(−1)~10^(−4)M level),and good recyclability(the binding capacity decreased less than 13%after ten times consecutive extraction)could also be observed for MNPs@B(OH)2.Finally,the BA-MSPE of polysaccharides was performed with three beverage plants as real samples,including tea leaves,soybeans,and Lycium barbarum.Antioxidant activity of polysaccharide extractives was verified by DPPH radical scavenging assays,giving a radical scavenging rate of 31.4%and 18.8%for crude extractives of TPS(tea polysaccharide)and LBPS(Lycium barbarum polysaccharide),respectively.Microscopic imaging combining with MTT and trypan blue staining trials uncovered that the extractives were of dosage-dependent antitumor bioactivities,giving the cell mortality rates over 91.8%and 77.2%for MCF-7 and A549 cells in the presence of 5.0 mg/mL TPS,and 56.6%and 40.0%with the equal dosage of LBPS,respectively.As the BA-MSPE strategy is simple and eco-friendly,there will be more potential for the application of cis-diol compound purification.