Ultrasound-assisted extraction (UAE) of antioxidant phenolics from Corchorus olitorius leaves: A response surface optimization

Abstract

Abstract This study was conducted to optimize the ultrasound-assisted extraction (UAE) parameters for total flavonoids and total polyphenols content from Corchorus olitorius leaves employing response surface methodology (RSM). Based on single-factor investigations, a four-factor-five-level Central Composite Design (CCD) with 30 experimental runs has been applied. Results demonstrated that all models were significant and had good accuracy of polynomial quadratic equations (p < 0.05) with a non-significant lack of fit at p > 0.05 and adjusted regression coefficient (R2) is > 0.95. Under the optimized conditions, the highest extraction yield of total flavonoids (TFC) (7.17 mg QE/g DW) and total polyphenol content (TPC) (13.92 mg GAE/g DW) were recorded with the ethanol concentration 70.92%, temperature 68.06 ºC, liquid-solid ratio 48.80 mL/mg, and ultrasound irradiation time 37.20 min. The optimum value of TFC (6.96 mg QE/g DW) and TPC (13.38 mg GAE/g DW) from the experiment of validation of optimized conditions, that were close to the predicted value and significantly superior to the conventional heat reflux extraction (HRE). Furthermore, the antioxidant test of the leaves extracts revealed an excellent 2,2-diphenyl-1-picrylhydrazyl (DPPH•), 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+•) and hydroxyl radical scavenging with IC50 values of 226.29, 199.53 and 402.02 µg/mL, respectively. The results indicate that optimization of UAE extraction conditions is essential for recovery of bioactive compounds in pharmaceuticals and food industries.