Optimization of ultrasound-assisted extraction of bioactive compounds from peony root (Paeonia japonica)

Peony root is a medicinal plant containing potent bioactive compounds. This study used response surface methodology (RSM) to optimize ultrasonic-assisted extraction (UAE) conditions of antioxidant compounds from peony roots. A central composite design consisting of extraction temperature (30-70℃), ethanol concentration (20-100% v/v), and extraction time (15-55 min) was used to determine the significance of each extraction condition on the total polyphenol, paeoniflorin, and myricetin contents and 2,2¢-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)scavenging activity of the extracts. The ABTS-scavenging activity and myricetin content increased with an increasing extraction temperature. Further, at low ethanol concentrations, paeoniflorin and myricetin contents increased. Superimposition of 4D graphs revealed that an extraction temperature of 60-65℃, ethanol concentration of 40-50%, and extraction time of 40-50 min were optimal extraction conditions for peony root. A validation experiment was conducted using 45% ethanol at 63℃ for 45 min. Under these UAE conditions, the experimental values of total polyphenol, paeoniflorin, and myricetin contents, and ABTS-scavenging activity were 101.80 mg GAE/g, 46.87 mg/g, 184.30 mg/g, and 23.13%, respectively. The validation experiment revealed slight differences between the experimental and predicted values (less than 10%), confirming the optimal UAE conditions for obtaining peony root antioxidant compounds via RSM. This study provides valuable information in developing functional food, medicine, and cosmetic using peony root extracts.