Optimization of the extraction of polyphenols and antioxidant activity from L. leaves using Box-Behnken design.

Box-Behnken Design (BBD) was used to optimize the extraction conditions of polyphenols from Malva ( L.) leaves. The effect of ethanol concentration (20-80%), solvent/leaf powder ratio (10:1 to 30:1, v/w) and extraction time (5-45 min) on the polyphenols yield and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of the obtained extracts were investigated. Quadratic models fit well. The optimal conditions (53.40% ethanol, solvent/leaf powder ratio 20:1 (v/w), and 15 min) resulted in an extract with a maximum yield of polyphenols (1098.4 mg GAE/100 g leaf powder) and high inhibition percentage of DPPH radical (33.31%) with desirability 0.742. High Performance Liquid Chromatography (HPLC) analysis indicated that the major identified polyphenol compounds extracted at the optimal conditions were naringenin, ρ-coumaric acid, apigenin-7-glucoside, luteolin, and cinnamic acid. These findings indicate that leaf extracts possess DPPH radical scavenging activity and could be used as a natural source for bioactive products.