Changes in polysaccharides structure and bioactivity during Mesona chinensis Benth storage

Abstract

Mesona chinensis Benth has been consumed as a functional food for many years. It is widely believed that storage times affect its health benefits. In this study, Mesona chinensis Benth polysaccharides with two different storage times (fresh and storage for 1 year) were prepared, namely, FMP and AMP. The physicochemical properties and bioactivity were comparatively assessed. Results indicated that FMP was mainly composed of galacturonic acid, galactose, and glucose with a molecular weight of 44.39 kDa. AMP was composed of galacturonic acid, galactose, and fructose with a molecular weight of 64.34 kDa. However, the principal structural characteristics of polysaccharides remained stable. Furthermore, assays of antioxidant activity showed that Mesona chinensis Benth polysaccharide had an antioxidant effect against DPPH radical, ABTS radical cation, among which FMP was stronger. Additionally, flow cytometry indicated that the apoptosis rate of FMP and AMP on HepG2 tumor cells was 22.50 ± 1.25% and 15.49 ± 1.30%, respectively. In general, antioxidant and antitumor activities of Mesona chinensis Benth polysaccharides were decreased as the storage for 1 year. The change of physicochemical properties was responsible for the enhanced bioactivities. These results explained how polysaccharides contributed to the decreased health benefits of Mesona chinensis Benth during storage.

Keywords: Antioxidant; Antitumor; Mesona chinensis Benth; Polysaccharides; Properties.

Graphical abstract

Fig. 1

UV–vis and FT-IR spectra of AMP and FMP. (A) UV–vis spectra were recorded in the range of 200–400 nm. (B) FT-IR spectrum.

Fig. 2

Microstructure images of AMP and FMP. SEM images of AMP (A: × 500, B: × 2000) and FMP (C: × 500, D × 2000); AFM images of AMP and FMP.

Fig. 3

Biological activities of AMP and FMP. (A) DPPH assay; (B) ABTS assay; (C) Cell viability assay; Effects of polysaccharide treatment on the apoptosis in HepG2 cells ((D) Quantitative presentation of apoptosis; (E) Blank (untreated) cells; (F) cells treated with 400 μg/mL AMP; (G) cells treated with 400 μg/mL FMP). Values are expressed as means ± SD (n = 3), different letters indicated a different significance (p < 0.05) among all the groups.

Fig. 4

Functional properties of AMP-WS and FMP-WS. (A) Gel strength; (B) steady shear viscosity; (C) complex viscosity. Values are expressed as means ± SD (n = 3), different letters indicated a different significance (p < 0.05) among all the groups.

Fig. 5

Rheological properties of AMP-WS and FMP-WS. (A) Storage modulus G’; (B) Loss modulus G’’; (C) The phase angle (tanδ).