**3. Results and Discussion**

#### *3.1. Physicochemical Properties and Molecular Weight*

In Table 1, the yield of CYP obtained from Chinese yam was 0.21 ± 0.01%, and the contents of carbohydrate, uronic acid, protein were 33.62 ± 0.08%, 34.95 ± 0.21%, and 5.21 ± 0.26%, respectively. The finding indicated that CYP was an acidic polysaccharide. The molecular weight of CYP was 20.89 kDa based on T-series dextran as the standard.

**Table 1.** Chemical composition of CYP.


Data are expressed as the mean ± SD.

#### *3.2. Monosaccharide Compositions*

Monosaccharide compositions were determined by ion chromatography. The results demonstrated that CYP was composed of arabinose (Ara), galactose (Gal), glucose (Glu), mannose (Man), xylose (Xyl), rhamnose (Rha), galacturonic acid (GalA), and glucuronic acid (GluA) (Table 1). CYP mainly consisted of Gal (28.57%), GluA (11.28%), and GalA (37.59%), which indicated that Gal, Glu, and GalA might form the backbone structure of CYP. However, the result was different from the polysaccharides prepared by Huang et al. [34], which could be due to raw materials produced in different periods and different extraction methods.

#### *3.3. UV and FT-IR Spectrum Analysis*

UV spectrum analysis of CYP showed that there was no absorption at 260 and 280 nm (Figure 1A), which indicated that CYP barely contained nucleic acids and proteins. This finding was consistent with the previous physicochemical-property analysis [35]. As shown in Figure 1B, a broad and strong absorption peak at 3410 cm−<sup>1</sup> was attributed to the O–H stretching vibration, and a relatively weak absorption peak at 2910 cm−<sup>1</sup> was assigned to the C–H stretching vibration [36]. The absorption peak at 1646 cm−<sup>1</sup> might be caused by the O–H bending vibration [37]. A weak absorption band at 1420 cm−<sup>1</sup> could originate from the stretching vibration of the carboxyl symmetry [38], which proved the presence of uronic acid. It could be confirmed by the results of the physicochemical properties and monosaccharide composition of CYP. The absorption peak at 1250 and 1070 might be caused by the stretching vibration of C–O [39], indicating the presence of the pyranose ring [40]. Combined with the above analysis, CYP had a clear polysaccharide characteristic.

**Figure 1.** (**A**) UV-vis and FT-IR spectra of CYP (**B**) UV-vis spectra were recorded in the range of 200−400 nm. FT-IR spectra were recorded with a Nicolet 5700 FT-IR spectrometer between 400 and 4000 cm−<sup>1</sup> using the KBr-disk method.

#### *3.4. SEM Analysis*

Scanning electron microscopy (Figure 2) can observe the surface morphology of polysaccharides, providing direct information on their microscopic appearance. Different from most polysaccharides that have a granular shape [32], CYP consists of irregular pieces that were observed at low magnification. After the magnification of 2000 times, many polymerized polygonal pieces can be seen on the surface of turmeric polysaccharide [41], but the surface of CYP is relatively smooth. This finding may be due to the relatively small molecular weight of CYP.

**Figure 2.** SEM micrographs showing surface microstructure of CYP ((**A**–**C**), 500×, 1000×, 2000× respectively).

#### *3.5. Effect of CYP on IEC-6 Cells Viability*

The cell viability of different concentrations of CYP cultured with IEC-6 cells is shown in Figure 3A. Compared with the control group, IEC-6 cells co-cultured with three concentrations of CYP had comparable cell viability, indicating that CYP had no toxic effect on IEC-6 cells.

In constructing a model of cellular oxidative damage by stimulating IEC-6 cells with different concentrations of H2O2, all concentrations of H2O2 reduced the viability of IEC-6 cells in a dose-dependent manner (Figure 3B). The cell viability of the 300 μM group was 55.83% compared with the control group. Therefore, 300 μM H2O2 was used as the concentration of the model group for the subsequent experiments.

The cell viability of the model group was significantly reduced after H2O2 stimulation of the cells. The pre-protected polysaccharide group was able to effectively slow down this trend, where the cell viability of the high-concentration group was comparable to that of the control group (Figure 3C). Thus, CYP had a better protective ability to deal with the negative effects of H2O2, consistent with a previous report [42].

**Figure 3.** (**A**) Toxicity test of CYP on cell viability of IEC-6 cells (% of control), (**B**) Effects of H2O2 on cell viability of IEC-6 cells (% of control), (**C**) Effects of CYP on cell viability in H2O2-injured IEC-6 cells (% of control). Results shown are expressed as means ± SD (*n* = 3). # *p* < 0.05 compared with normal group, \* *p* < 0.05 compared with H2O2 group alone \*\* *p* < 0.01 compared with H2O2 group alone.
