Optimization protocol for the extraction of 6-gingerol and 6-shogaol from Zingiber officinale var. rubrum Theilade and improving antioxidant and anticancer activity using response surface methodology

Table 3 Regression coefficients, R², adjusted R² and F-values for dependent variables

	constant	linear	quadratic	Interaction
Responses	b₀	b₁	b₂	b₁²	b₂²	b₁₂	R²	R² (adjusted)	Regression (F value)	Lack of fit (F value)
Y₁	1.53	0.51	0.25	0.27	0.0092	0.31	0.97	0.95	45.91^**	4.12 ^n.s
Y₂	1.2	0.15	0.12	0.021	0.024	0.15	0.93	0.92	15.58^**	1.39 ^n.s
Y₃	71.88	9.22	2.78	3.16	1.11	4.63	0.96	0.94	15.79^**	1.24 ^n.s

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