Table 3.

Regression coefficient (β) and analysis of variance (ANOVA) of the predicted second-order polynomial models for phenolic compounds and antioxidant activity.

Factor	Coefficient (β)
	TPC	TFC	DPPH	ABTS
Intercept	83.19	15.04	53.93	67.44
Linear
X 1-conc	−1.20	−0.40	−1.61	−2.27∗
X 2-power	8.17∗∗∗	4.40∗∗∗	14.90∗∗∗	11.97∗∗∗
X 3-time	5.31∗∗	4.60∗∗∗	12.13∗∗∗	11.43∗∗∗
Interaction
X 1 X 2	−0.3750	−1.16∗	−0.8075	0.01
X 1 X 3	2.19∗	0.48	−1.13	0.47
X 2 X 3	−2.17∗	1.06∗	5.82∗∗	−0.34
Quadratic
X 1 2	−5.55∗∗	−4.32∗∗	−4.63∗	−22.82∗∗∗
X 2 2	−4.37∗	−3.56∗∗	−5.93∗∗	−0.80
X 3 2	−7.46∗∗	1.17	0.9999	−7.35∗∗
F-value (model)	31.33∗∗∗	61.66∗∗∗	87.93∗∗∗	76.60∗∗∗
F-value (lack of fit)	1.58	7.04	0.74	5.41
R 2	0.9758	0.9875	0.9912	0.9899
Adj-R2	0.9446	0.9715	0.9800	0.9770
Pred-R2	0.8086	0.8679	0.9372	0.9255
CV (%)	3.55	9.28	4.83	5.98

^∗ p < 0.05, ^∗∗p < 0.01, ^∗∗∗p < 0.001.