Optimization of Ultrasound-Assisted Extraction of Phenolic Compounds from Romanian Blackthorn ( L.) Fruits.

Selecting factors that significantly affect the extraction process and optimizing them are essential to obtain high extraction efficiency. This study aimed at optimizing the ultrasonic-assisted extraction (UAE) of polyphenols from Romanian blackthorn fruits using aqueous solutions of ethanol as green extraction solvents. Six process factors, including solvent/plant material ratio ( = 4.95-15.1 cm/g), ethanol concentration in the extraction solvent ( = 16.4-83.6%), extraction temperature ( = 30-70 °C), pH of the solvent ( = 2-7), amplitude of the ultrasonic probe ( = 30-70%), and extraction time ( = 5-15 min), were screened and optimized based on a Plackett-Burman design (PBD) and a central composite design (CCD). Statistical analysis indicated that , , and significantly affected the process response variables in terms of total phenolic content (), total anthocyanin content (), and antioxidant capacity (). Under optimal conditions ( = 15.1 cm/g, = 33.2%, = 66.8 °C, = 7, = 50%, and = 10 min), the following levels of response variables were experimentally determined: = 14.45 ± 0.718 mg GAE/g DM, = 0.405 ± 0.057 mg C3GE/g DM, and = 16.75 ± 1.144 mg TE/g DM. Six phenolic compounds were identified in the extract obtained at optimal levels of process factors, i.e., rutin (7.12 ± 0.06 mg/100 g DM), protocatechuic acid (6.83 ± 0.01 mg/100 g DM), neochlorogenic acid (4.88 ± 0.01 mg/100 g DM), vanillic acid (3.70 ± 0.01 mg/100 g DM), chlorogenic acid (1.93 ± 0.02 mg/100 g DM), and caffeic acid (1.51 ± 0.01 mg/100 g DM).