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The extract was separated from the wooden layer between of walnut seed using pressurized hot water extraction (PHWE), pressurized liquid extraction (PLE), and perculation methods A central composite design was used to optimize the effective extraction variables. For achieving maximum extraction yield, total phenolic and minimum 2,2-Diphenyl-1-picrylhydrazyl (DPPH) IC 50 using PHWE and PLE the temperature was 105 °C and 78 °C, respectively but the pressure, static time, dynamic time for two methods were 19 bar, 18.06 min, and 28.34 min, respectively. The extraction yield and total phenols of optimum PHWE extract were more than optimum PLE and perculation extracts. The radical scavenging effects of the tested extracts were concentration dependent and all samples with the highest concentration of extracts had strong scavenging effect. The PHWE optimum extract exhibited considerably highest DPPH free radical scavenging activity with lowest IC 50 than PLE and perculation methods. [ABSTRACT FROM AUTHOR]