Characterization, optimization of preparation process of an Inonotus obliquus polysaccharide-Zinc (II) complex and its antioxidant activities

Figures & data

Table 1. Independent variables and their levels in the response surface design.

Independent variables		Levels
		−1	0	1
X 1	Chelation time (h)	4	6	8
X 2	Zinc (II) initial concentration (mg/mL)	3	4	5
X 3	Mass ratio of IP3a to zinc sulfate heptahydrate (mg/mg)	3:1	4:1	5:1

Figure 1. Effect of chelation time (A), zinc (II) initial concentration (B) and mass ratio of IP3a to zinc sulfate heptahydrate (C) on chelation rate of IP3a-Zn.

Table 2. Result of response surface analysis of the variation of chelation rate of IP3a-Zn with chelation time (X₁), Zinc (II) initial concentration (X₂) and mass ratio of IP3a to zinc sulfate heptahydrate (X₃).

Runs	Factors			Chelation rate (%)
	X 1	X 2	X 3
1	1	−1	0	89.2
2	0	−1	−1	72.1
3	0	0	0	89.2
4	0	0	0	89.2
5	−1	0	−1	64.2
6	0	1	1	76.2
7	1	1	0	66.3
8	0	1	−1	78.1
9	−1	0	1	71.2
10	−1	−1	0	52.3
11	1	0	−1	78.2
12	0	0	0	89.2
13	1	0	1	69.5
14	0	0	0	89.2
15	0	0	0	89.2
16	0	−1	1	61.2
17	−1	1	0	65.2

Table 3. ANOVA for response surface quadratic model.

Source	Sum of squares	Df	Mean squares	F-value	P-value
Model	1450.88	9	161.21	36.64	<0.0001	**
X 1	106.58	1	106.58	24.22	0.0017	**
X 2	127.20	1	127.20	28.91	0.0010	**
X 3	26.28	1	26.28	5.97	0.0445	*
X 1 X 2	55.50	1	55.50	12.62	0.0093	**
X 1 X 3	61.62	1	61.62	14.01	0.0072	**
X 2 X 3	20.25	1	20.25	4.60	0.0691
X 1 ^2	525.81	1	525.81	119.51	<0.0001	*
X 2 ^2	425.27	1	425.27	96.66	<0.0001	**
X 3 ^2	21.32	1	21.32	4.84	0.0636
Residual	30.80	7	4.40
Lack of fit	30.80	3	10.27	10.72	0.0723
Pure error	0.000	4	0.000
Cor total	1481.68	16

Note: Asteriscs indicate significant differences (*p < 0.05; **p < 0.01).

Figure 2. Response surface plots showing the effect of chelation time and zinc (II) initial concentration (A), chelation time and mass ratio of IP3a to zinc sulfate heptahydrate (B) and zinc (II) initial concentration and mass ratio of IP3a to zinc sulfate heptahydrate (C) on chelation rate of IP3a-Zn.

Table 4. Results of determination of zinc content in IP3a-Zn and IP3a.

Sample	Zinc content (%)
IP3a	0
IP3a-Zn	7.83 ± 0.52

Figure 3. FT-IR spectroscopy analysis of IP3a-Zn and IP3a.

Figure 4. Scanning electron microscope image of IP3a (A) and IP3a-Zn (B) at 5000×.

Figure 5. X-ray diffraction spectrum profile of IP3a and IP3a-Zn.

Figure 6. Thermogravimetric curve of IP3a and IP3a-Zn.

Figure 7. Scavenging effect of IP3a and IP3a-Zn on superoxide anion free radical (A), hydroxyl free radical (B) and DPPH free radical (C).

Data availability statement

All data that support the findings reported in this study are available from the corresponding author upon reasonable request.