In this study, a surfactant-mediated ultrasonic-assisted process was used for the first time to produce an antioxidant-enriched extract from Chaenomeles speciosa (Sweet) Nakai (C. speciosa, a popular fruit grown widely in the temperate regions of China). Ultrasonic treatment at 51 °C and 200 W for 30 min with sodium dodecyl sulfate as the surfactant led to a phenolic yield of 32.42 mg/g from dried C. speciosa powder, based on single-factor experiments, the Plackett–Burman design and the Box–Behnken design. The phenolic content increased from 6.5% (the crude extract) to 57% (the purified extract) after the purification, using LSA-900C macroporous resin. Both the crude and purified extracts exhibited a significant total reducing power and DPPH/ABTS scavenging abilities, with the purified extract being more potent. The purified extract exerted significant antioxidant actions in the tert-butyl hydroperoxide-stimulated HepG2 cells, e.g., increasing the activities of superoxide dismutase and catalase, while decreasing the reactive oxygen species and malondialdehyde levels, through the regulation of the genes and proteins of the Nrf2/Keap1 signaling pathway. Therefore, the extract from C. speciosa is a desirable antioxidant agent for the oxidative damage of the body to meet the rising demand for natural therapeutics.

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In this paper, the optimal extraction process of polyphenols from Chaenomeles sinensis (Thouin) koehne was studied by single factor test and response surface test. Research results showed that the optimum extraction conditions were as follows: enzymatic time 55 min, ethanol concentration 59%, enzymatic liquid-material ratio 28:1 mL/g, pectinase amount 20 μL/g, enzymatic pH 3.4, enzymatic temperature 65°C, ultrasonic liquid-material ratio 30:1 mL/g, ultrasonic time 40 min, ultrasonic temperature 55°C. Under these conditions, the extracted content of Chaenomeles sinensis (Thouin) koehne polyphenols was 62.07 mg/g.

Chestnut shell is one of the main by-products in the chestnut processing, which contains abundant polyphenols, so it can be used as a source of polyphenols. In this study, using ethanol as the extraction solvent, the optimum extraction conditions of polyphenols from chestnut shell were determined by single factor experiment and response surface experiment: liquid-solid ratio of 39:1, extraction temperature of 74°C, extraction time of 91 min, ethanol concentration of 65%. Under these conditions, the extraction rate (ER) of polyphenols from chestnut shell was 6.09%. The results can assist in better exploitation of chestnut shell, which can not only reduce resource waste and environmental pollution, but also obtain economic benefits.

Paeonia suffruticosa (P. suffruticosa) seed meal is a byproduct of P. suffruticosa seed processing, which contains bioactive substances such as monoterpene glycosides, and has not been effectively utilized at present. In this study, monoterpene glycosides were extracted from P. suffruticosa seed meal using an ultrasound-assisted ethanol extraction process. The monoterpene glycoside extract was then purified by macroporous resin and identified using HPLC-Q-TOF-MS/MS. The results indicated the following optimal extraction conditions: ethanol concentration, 33%; ultrasound temperature, 55 °C; ultrasound power, 400 W; liquid–material ratio, 33:1; and ultrasound time, 44 min. Under these conditions, the yield of monoterpene glycosides was 121.03 mg/g. The purity of the monoterpene glycosides increased from 20.5% (crude extract) to 71.2% (purified extract) when using LSA-900C macroporous resin. Six monoterpene glycosides (oxy paeoniflorin, isomaltose paeoniflorin, albiflorin, 6′-O-β-D-glucopyranoside albiflorin, paeoniflorin, and Mudanpioside i) were identified from the extract using HPLC-Q-TOF-MS/MS. The main substances were albiflorin and paeoniflorin, and the contents were 15.24 mg/g and 14.12 mg/g, respectively. The results of this study can provide a theoretical basis for the effective utilization of P. suffruticosa seed meal.