Chemical and rheological properties of proteoglycans from Sarcandra glabra (Thunb.) Nakai.

Two proteoglycans (HPP and LPP) with different ratios of protein/polysaccharide were extracted from S. glabra. The chemical compositions, relative average molecular weights, monosaccharide compositions, FT-IR spectra, and rheological properties of the two proteoglycans were determined. The results exhibited that the two proteoglycans had pseudoplastic fluids properties and displayed shear-thinning behavior. The apparent viscosity of the two proteoglycans both increased with increasing concentrations. The temperature had different effects on the viscosity of the two proteoglycans. As temperature increased from 25 to 85 °C, the viscosity of LPP descended while the HPP's viscosity rose first and then dropped slightly. The effects of CaCl₂ addition on the two samples were like that of the temperature. The viscosities of HPP and LPP had different tolerances to acidity and alkalinity. HPP solution was more sensitive to pH changes due to its high protein content. The addition of sucrose increased the viscosities of samples. The modulus G' and G″ of HPP and LPP were increased with the increase of oscillation frequency, while the crossover points of G' and G″ values decreased with the increasing concentrations of HPP and LPP. The above data presented that the two proteoglycans could be promising candidates for food industries and pharmacological applications.