The extraction of bioactive medicinal plants can be affected by solvent, temperature, and extraction time. This work describes the optimization of the extraction process of phenolic antioxidants from Justicia gendarussa Burm f. leaves based on response surface methodology. The independent variables used in the experimental design were ethanol concentration (10%, 50%, and 90%), temperature (30°C, 45°C, and 60°C), and time (60, 120, and 180 minutes). The total phenolic content (TPC) and antioxidant activity of 2,2-diphenyl-1-picrylhydrazyl were used as responses. The results for phenolic antioxidants were maximized, producing a desirability value of 0.918. The optimum formula for extracting J. gendarussa leaves was at an ethanol concentration of 30%, a temperature of 30°C, and an extraction time of 180 minutes, which resulted in a TPC content of 8.29 mg gallic acid equivalent/g dry weight (DW) and DPPH antioxidant activity of 4.010 μmol trolox equivalent/g DW. The predicted value is in accordance with the verification results for the best extraction conditions, as evidenced by the % percent residual standard error TPC and antioxidant activity, 4.465% and 7.082%, respectively. Sonication with the maceration extraction procedure can significantly increase the extraction of phenolic antioxidants from J. gendarussa leaves. This is a valuable method for extracting essential phenolic antioxidants from medicinal plants.
Key words: Antioxidant, maceration, phenolic, response surface methodology, sonication, Justicia gendarussa
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