Optimization of Bioactive Compound and Phytochemical Extraction From Prickly Pear ( <i>Opuntia ficus-indica</i> ) Fruit Through Ultrasound‐Assisted Extraction (UAE)

Opuntia ficus-indica (prickly pear fruit, PPF) as a rich source of natural antioxidants and colorants was aimed to be extracted (PPFE) through optimization by response surface methodology and central composite design (CCD) using ultrasound‐assisted extraction (UAE). The effects of independent variables including ethanol concentration (0%, 24%, 48%, 72%, and 96%), citric acid concentration (0%, 0.25%, 0.50%, 0.75%, and 1%), and ultrasound power (0, 100, 200, 300, and 400 W) were investigated. Total phenol content (TPC), total flavonoid content (TFC), total betalain content (TBC), DPPH radical scavenging activity (RSA), and ferric reducing antioxidant power (FRAP) were determined. Based on the results, higher TPC, TFC, and TBC were obtained for PPFE when higher ultrasound power (300 W) was exerted. Ethanol concentration had an inverse relation with TPC and TFC, and higher concentration led to a reduction in respective properties. Acidifying the media by citric acid positively influenced the extraction of phenolic, flavonoid, and betalain compounds. DPPH RSA was negatively affected by ethanol concentration–ultrasound power and citric acid–ultrasound power interactions. Ethanol concentration negatively influenced FRAP, as well as observed for TPC. The optimal point was obtained at an ethanol concentration of 31.50%, citric acid concentration of 0.074%, and ultrasound power of 400 W, which rendered 1.97 mg GAE/g fresh fruit, 3.75 mg quercetin/g fresh fruit, 1.05 mg/100 g fresh fruit, 55.35%, and 5.60 mg Fe 2+ /g fresh fruit for TPC, TFC, TBC, DPPH RSA, and FRAP value, respectively. Overall, PPFE can be incorporated into foods as natural antioxidants and colorants.