Application of response surface methodology to optimize celery (Apium graveolens L.) aerial part extraction and its phenolic compounds and antioxidant activity using ultrasound-assisted

In this research, the effect of time (10, 15, 20, 25 and 30 min) and temperature (35, 45, 55, 65 and 75 oC) of ultrasonic waves, ethanol to water ratio (20, 35, 50, 65 and 80%) of extracting solvent and dry matter to solvent ratio (1:5, 1:10, 1:15, 1:20 and 1:25 mg/ml) was investigated on total phenol and flavonoids and antioxidant capacity (in two methods of DPPH and FRAP) of hydroalcoholic extract of celery (Apium graveolens L.) aerial parts by using the response surface method. Based on the results, ultrasound for 10 min at 55 °C, ethanol to water ratio of 80%, and dry matter to solvent ratio of 1:5 were considered as the best treatment. The highest amount of total phenol (471.1 mg GAE/g DW) and flavonoid (187.7 mg quercetin/gDW) content, and antioxidant activity of the extract was obtained under optimized conditions using DPPH (68.5%) and FRAP (4210.4 μM Fe+2/50 μl extract). In general, the high values of adjusted R2 and P-value in fitting models indicated that the drawn models of response surface were ideal. In other words, the high amounts of these parameters indicate the existence of a correlation between the observed values and the predicted ones.