Optimization of the pulsed electric field -assisted extraction of functional compounds from Nepeta binaludensis

Abstract

Pulsed electric field (PEF) treatment was used for extracting effective components from Nepeta (Nepeta binaludensis Jamzad). A response surface method was used to investigate the effects of independent process variables (voltage of pulsed electric field (VPEF): 2, 4 and 6 KV/cm and number of pulsed electric field (NPEF): 20, 40 and 60 n) on the yield (Y) and antioxidant characteristics: total phenolic compounds (TPC), 1,1- diphenyl -2- picrylhydrazyl free radical scavenging (DPPH_sc), ferric reducing-antioxidant power (FRAP), half  maximal of radical-scavenging activity (IC₅₀) of Nepeta extract (aerial parts). According to Derringer’s desired function approach, the optimal conditions based on both individual and combinations of all process variables were VPEF 6KV/cm and NPEF 60 n. At this optimum condition, the Y, TPC, DPPH_SC, FRAP, and IC₅₀ of the extract were found to be 11.36%, 417.85 mg GA/g, 74.8%, 1688.53µmol Fe²⁺/g, and 0.32 mg/mL, respectively. The experimental values were in a good agreement with the predicted values. Also, the extract at optimal conditions of PEF (PEF_opt-x) had a higher quantity of chlorogenic acid, caffeic acid, rutin, para-coumaric acid, rosemarinic acid, Kaempferol, and apigenin compared with solvent extract. The addition of PEF_opt-x to the purified soybean oil at the levels of 6% increased oxidative stability index (2.65 h) close to butylated hydroxy toluene (2.78h).