Table 7.

Experimental plan for the isolation of polyphenolic antioxidants from wild thyme.

I Step—Screening of the Extraction Solvent
Approach	Constant Parameters	Factors	Responses *
OFAT 1	Sample to solvent ratio: 1:20 m/mTemperature: 50 °C Extraction time: 60 min Stirring speed: 700 rpm Water content: 20%	NADES: N1–N20	TP 2 DPPH 3
II Step—Preliminary Study
Approach	Constant Parameters	Factors	Responses
25−1 fractional factorial design	Stirring speed: 700 rpm	Temperature: 50 and 60 °C Extraction time: 60 and 120 min Sample to solvent ratio: 1:10 and 1:20 m/m NADES: N15 and N16 Water content: 20 and 25%	TP DPPH
III Step—Optimization
Approach	Constant Parameters	Factors	Responses
RSM	NADES: N16 Water content: 20% Stirring speed: 700 rpm	Temperature: 40, 55 and 70 °C Extraction time: 60, 120 and 180 min Sample to solvent ratio: 1:10, 1:20 and 1:30 m/m	TP TF 4 DPPH FRAP 5 ABTS 6

* maximized, ¹ One-factor-at-a-time, ² total phenol content, ³ antioxidant activity toward DPPH radicals, ⁴ total flavonoids content, ⁵ reducing activity towards Fe³⁺ ions, ⁶ antioxidant activity towards ABTS+ radicals.