Optimization of Phenolic Compounds and antioxidant activity of the extract of Ziziphora clinopodioides using Ultrasound-assisted Extraction whit Response Surface Methodology

In this laboratory study, the optimization process of ultrasound-assisted extraction (UAE) of phenolic compounds of Ziziphora clinopodioides was done using response surface methodology (RSM). For the determination of total phenolic compounds and antioxidant activity of the extracts, Folin test and DPPH assay were used, respectively. A central composite design for optimization of process parameters with three independent variables included time (2, 6.5, 13.5, 20 and 25 min), the solvent concentrations (0, 20, 50, 80 and 100% of water in ethanol) and the ratio of solvent to solids (10, 14, 20, 26 and 30 solvents on the dry matter), which includes 18 test at five levels with four replicates at the central point was done. Correlation coefficients (R2) of the models for total phenolics and antioxidant activity were 0.98 and 0.93, respectively. The results of the optimization for the extraction of phenolic compounds showed that the extraction in terms of time 18.29 min, the solvent concentration of 22.15% and the ratio of solvent to solids 25.95 were the highest amount of phenolic compounds about 7.81 mg of gallic acid equivalents per gram of dry matter. Optimal conditions in terms of antioxidant activity were the ratio of solvent to solids 14.77, time 6.66 min, solvent concentration 23.37%, respectively, under these conditions, the amount of the antioxidant activity of 14.25% per gram of dry matter was obtained.