2.4 Experimental design
Box Behnken Design (BBD) was used to experimental design purpose that
includes the variables and three factorial levels. The independent
variable used in the study were methanol concentration
(X1, %, v/v), extraction temperature
(x2, °C) and time (x3, min) while response variable was
DPPH and ABTS free radical scavenging activity. Supplementary table 1
exhibited the coded and uncoded levels of independent variables. The
center point of variable stands for coded value (0) and repeated
experimental error. Factorial points were coded as ± 1.