Isolation, purification and characterisation of selenium-containing polysaccharides and proteins in selenium-enriched Radix puerariae

Abstract

Selenium (Se) is an essential dietary mineral and Radix puerariae (RP) (the dried root of Pueraria lobata Willd.) is a botanical supplement widely used as a nutraceutical. Food enriched with Se provides a feasible and economic approach for production of organic Se compounds. However, little is known about Se-enriched RP and the structure of Se-containing polysaccharides and proteins derived from Se-enriched RP. The organic form of Se accounted for 82.42% of total content. Purification by DEAE-52 and Sephadex G-100 column chromatography yielded three single fractions--RP-SeP-11, RP-SeP-22 and RP-SeP-33--with Se contents of 0.9562 × 10⁻³, 0.6113 × 10⁻³ and 0.3827 × 10⁻³ g kg⁻¹, respectively. RP-SeP-11 (3.5 kDa) was made of glucose, RP-SeP-22 (19.6 kDa) was composed of xylose and glucose, and RP-SeP-33 (97.9 kDa) was made up galactose, mannose and glucose. Two Se-containing proteins were obtained with Se content of 3.175 × 10⁻³ and 4.328 × 10⁻³ g kg⁻¹, respectively. One appeared as three subunits with molecular masses of 43.0, 29.0 and 17.8 kDa while the other appeared as two subunits with molecular masses of 43.0 and 26.3 kDa. The results provide a basis for promoting the utilisation of RP resources enriched with Se as a promising tool for the food industry and are significant for its contribution to Se biochemistry in plants.