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.