Optimization of ultrasonic-assisted extraction of bioactive compounds from Nepeta (Nepeta binaludensis Jamzad)

Ultrasonication technology was utilized for extraction of effective components from Nepeta (Nepeta binaludensis Jamzad). Response surface methodology was employed in order for investigation the effects of independent process variables (ultrasonic extraction time (UET, min): 5, 10 and 15 min, ultrasound amplitude (UA, %): 20, 60 and 100%, ultrasonic extraction temperature (UEC, degrees C): 25, 35 and 45 degrees C and ultrasonic duty cycle (UDC, %): 20, 60 and 100%) on the yield (Y), total phenolic compounds (TPC), half maximal of radical (1,1-diphenyl-2-picryl hydrazyl, DPPH) scavenging activity (IC50) and ferric reducing-antioxidant power (FRAP) of ethanolic Nepeta extract. According to Derringer's desired function approach, the optimal conditions based on both individual and combinations of all process variables were UET 15 min, UA 60%, UEC 25 degrees C and UDC 60%. At this optimum condition, the Y, TPC, IC50 and FRAP of the ultrasound-assisted extract (USx) were found to 10.93%, 402.63 mg GA/kg, 0.33 mg/mL and 2838.34 mu mol Fe2+/kg, respectively which were well matched with the predicted values. The evaluation of antioxidant activity (IC50 and FRAP) indicates that the phenolic compounds from Nepeta possess significant antioxidant activity. Also, HPLC analysis revealed that at optimal condition of UAE, the quantity of caffeic acid (85.71%), rutin (3550%) and rosemarinic acid (468.62%) in extract increased in comparison with conventional method (solvent extraction).