Optimization of Ultrasonic Extraction of Phenolic Compounds from Epimedium brevicornum Maxim Using Response Surface Methodology and Evaluation of Its Antioxidant Activities In Vitro

Table 1

Independent variables and their levels used in the response surface design.

Factor	Notation	level
		−1.682	−1	0	1	1.682
Ethanol concentration (%) (v/v)		20	32.16	50	67.84	80
Ultrasonic extraction time (min)		5	14.12	27.5	40.88	50
Liquid-solid ratio (mL/g)		50	90.55	150	209.45	250