Optimization of microwave-assisted extraction conditions for preparing lignan-rich extract from Saraca asoca bark using Box–Behnken design

Figures & data

Table 1. The Box–Behnken experimental design with the independent variables (actual and coded values).

Run	A (Solvent ratio)	B (Material to solvent ratio)	C (Extraction time)	Actual yield (mg/g)	Predicted yield (mg/g)
1	90.00 (+1)	30.00 (+1)	20.00 (0)	7.78 ± 0.015	7.79
2	70.00 (0)	20.00 (0)	20.00 (0)	8.28 ± 0.03	8.32
3	90.00 (+1)	20.00 (0)	20.00 (0)	7.2 ± 0.15	7.15
4	70.00 (0)	30.00 (+1)	30.00 (+1)	8.22 ± 0.075	8.19
5	70.00 (0)	20.00 (0)	20.00 (0)	8.29 ± 0.025	8.32
6	50.00 (−1)	10.00 (−1)	20.00 (0)	6.58 ± 0.025	6.56
7	70.00 (0)	30.00 (+1)	10.00 (−1)	9.28 ± 0.05	9.27
8	70.00 (0)	20.00 (0)	20.00 (0)	8.3 ± 0.06	8.32
9	90.00 (+1)	10.00 (−1)	20.00 (0)	7.01 ± 0.055	6.99
10	50.00 (−1)	30.00 (+1)	20.00 (0)	7.51 ± 0.06	7.52
11	70.00 (0)	10.00 (−1)	30.00 (+1)	7.74 ± 0.03	7.75
12	70.00 (0)	20.00 (0)	20.00 (0)	8.39 ± 0.045	8.32
13	90.00 (+1)	20.00 (0)	30.00 (+1)	6.56 ± 0.083	6.567
14	50.00 (−1)	20.00 (0)	30.00 (+1)	6.2 ± 0.08	6.20
15	70.00 (0)	10.00 (−1)	10.00 (−1)	7.92 ± 0.15	7.94
16	70.00 (0)	20.00 (0)	20.00 (0)	8.38 ± 0.065	8.32
17	50.00 (−1)	20.00 (0)	10.00 (−1)	6.86 ± 0.055	6.85

Table 2. Analysis of variance for the fitted quadratic polynomial model of extraction of lyoniside.

Source	Sum of squares	Degree of freedom	Mean square	F-value	Prob>F
Model	11.05	9	1.23	615.02	<0.0001	Significant
Residual	0.014	7	1.997E–003
Lack of fit	2.900E–03	3	9.667E–003	0.35	0.7932	Not significant
Pure error	0.011	4	2.770E–003

Table 3. Estimated regression model of the relationship between extraction yield of lyoniside and independent variables (A, B, C).

Variable	Degree of freedom	Sum of squares	F-value	p Value
AB	1	6.400E–003	3.20	0.1166
AC	1	1.000E–004	0.050	0.8293
BC	1	0.19	96.94	<0.0001
A^2	1	7.63	3822.43	<0.0001
B^2	1	0.24	119.92	<0.0001
C^2	1	0.32	161.18	<0.0001

Figure 1. Response surface plot and contour plot showing the effect of solvent ratio (A) and material solvent ratio (B) on lyoniside content.

Figure 2. Response surface plot and contour plot showing the effect of solvent ratio (A) and time (C) on lyoniside content.

Figure 3. Response surface plot and contour plot showing the effect of material solvent ratio (B) and time (C) on lyoniside content.

Figure 4. HPLC chromatogram of optimized extract and structure of lyoniside.

Figure 5. Mass spectra of lyoniside.

Table 4. Optimum conditions and the predicted and experimental yield at the optimum conditions.

	(A) Solvent ratio	(B) Material solvent ratio	(C) Time	Lyoniside content
Optimum conditions	70.96	30.00	10.27	9.27
Actual conditions	70	30	10	9.4 ± 0.11

Figure 6. Correlation plot between the actual and predicted yield of lyoniside content.