Ultrasound-assisted extraction of Ehretia macrophylla wall. Fruit phenolic acids: Process optimization,...

Ehretia macrophylla Wall. fruit (EMF) is rich in phenolic acids and is commonly used as an ethnomedicine against respiratory diseases. In this study, ultrasound-assisted extraction (UAE) was employed to obtain the optimal extract of EMF phenolic acids (EMFPA). The chemical components of EMFPA were characterized, and its antioxidant, anti-inflammatory, and lung protective activities were systematically evaluated. Using a Box-Behnken response surface methodology design, the optimal UAE conditions were determined to be ultrasound power of 350 W, a time of 67 min, a temperature of 53℃, and a liquid-to-solid ratio of 45:1 mL/g, resulting in the highest extraction yield value of EMFPA (84.32 ± 0.21 mg CA/g), which was significantly higher than that obtained with ethanol reflux extraction (ERE). A total of 31 phenolic acids were identified in EMFPA by UPLC-Q-TOF/MS, including protocatechualdehyde, caffeic acid, and rosmarinic acid derivatives. Quantitative analysis revealed that UAE yielded higher major phenolic acids than ERE, especially salvianolic acid A. The antioxidant activity of UAE-EMFPA was substantially higher than that of the ERE-EMFPA, and the UAE-EMFPA had a concentration dependent inhibitory effect on NO, TNF-α, and IL-6 generation in the LPS-induced MLE-12 cell inflammatory model. Furthermore, EMFPA treatment markedly reduced the W/D ratio, alleviated inflammatory cell infiltration, and mitigated the histopathologic injuries in LPS-induced acute lung injury mouse model. These findings fully confirm that UAE is a superior method for EMFPA extraction, and that EMFPA is a potential natural active for developing lung-protective functional foods or pharmaceuticals.