Optimization of Gentisides Extraction from Gentiana rigescens Franch. ex Hemsl. by Response Surface Methodology

Table 1

Box-Behnken design and the actual and coded values of the independent variables.

Run	Extraction temperature	Extraction time	Solvent-material ratio	Gentisides yield
	: °C	: h	: mL/g	: (%)
1	0 (75)	0 (3)	0 (10)	95.7591
2	0 (75)	−1 (2)	−1 (8)	81.2493
3	0 (75)	0 (3)	0 (10)	101.9360
4	−1 (65)	0 (3)	−1 (8)	65.4543
5	−1 (65)	0 (3)	+1 (12)	76.8498
6	0 (75)	0 (3)	0 (10)	92.8269
7	0 (75)	−1 (2)	+1 (12)	89.7775
8	0 (75)	0 (3)	0 (10)	91.9897
9	+1 (85)	+1 (4)	0 (10)	65.7978
10	0 (75)	+1 (4)	+1 (12)	89.2336
11	0 (75)	+1 (4)	−1 (8)	95.8044
12	0 (75)	0 (3)	0 (10)	107.89
13	+1 (85)	0 (3)	+1 (12)	68.1115
14	+1 (85)	−1 (2)	0 (10)	65.8044
15	−1 (65)	−1 (2)	0 (10)	50.0952
16	+1 (85)	0 (3)	−1 (8)	66.9001
17	−1 (65)	+1 (4)	0 (10)	78.1553