Table 2.

Analysis of variance and regression coefficients of predicted quadratic polynomial models with the ultrasonic-assisted extraction conditions on the soluble phenolic content from J. spicigera leaf extracts

Source1	Analysis of variance				Regression coefficients
	SS2	DF3	MS4	F Value	Soluble phenolic content β–coefficient
Mean/intercept	–	–	–	–	− 31.489*
X1	17.15	1	17.15	38.18*	179.609*
${\text{X}}_1^2$	365.93	1	365.93	601.34*	− 136.002*
X2	22.42	1	22.42	36.84*	0.134**
${\text{X}}_2^2$	178.99	1	178.99	294.12*	0.001**
X3	147.02	1	147.02	241.60*	2.039*
${\text{X}}_3^2$	25.64	1	25.64	42.14*	− 0.061*
X1 * ${\text{X}}_2^2$	8.90	1	8.90	14.63*	− 0.007*
${\text{X}}_1^2$ * X2	29.918	1	29.91	49.16*	0.618*
X1 * X3	64.57	1	64.57	106.11*	− 7.320*
${\text{X}}_1^2$ * X3	20.66	1	20.66	33.95*	4.124*
X2 * X3	72.52	1	72.52	119.17*	0.016*
Lack of Fit	4.15	1	4.15	6.83**
Pure Error	19.47	32	0.608
R-square	0.978
R-Adjust	0.969
Total SS	1015.92

¹Pulses cycle (X_PC); Sonication Amplitude (X_SA) and Extraction Time (X_ET)

²SS, sum of square

³DF, degree of freedom

⁴MS, means square

*Significant (p < 0.01); **nonsignificant (p > 0.01)