Ultrasound-Assisted Extraction of Phenolic Compounds from Moroccan Lavandula stoechas L.: Optimization Using Response Surface Methodology

Table 5

Estimated regression coefficients for the response total polyphenol concentration and their level of significance value.

Term	Coefficient	Estimation	Standard deviation	‐value
Constant		91.86	8.258	0.0001
Extraction time		−15.459	5.057	0.028
Solvent-to-material ratio		−3.655	5.057	0.502
Ethanol (%)		−16.226	5.057	0.024
Extraction time  solvent-to-material ratio		−8.01	7.151	0.314
Extraction time  ethanol (%)		−3.538	7.151	0.642
Solvent-to-material ratio  ethanol (%)		−10.57	7.151	0.199
Extraction time  extraction time		36.634	7.443	0.004
Solvent-to-material ratio  solvent-to-material ratio		27.741	7.443	0.014
Ethanol (%)  ethanol (%)		3.994	7.443	0.615

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