Ultrasound-assisted aqueous two-phase extraction of flavonoids from erigeron breviscapus: process optimization, structural characterization, antioxidant study, and DFT calculation

The well-known medicinal plant Erigeron breviscapus has long been used to treat cerebral embolism, cerebral thrombosis, and cerebral hemorrhage. Response surface methodology (RSM) was applied to optimize the ultrasonic-assisted extraction process of total flavonoids from Erigeron breviscapus (EBTF) using aqueous two-phase system. The flavonoids from E. breviscapus were qualitatively identified using UPLC-Q-TOF-MS/MS. The capacity of EBTF to scavenge · OH was used to assess its antioxidant activity. To determine the active sites in the primary bioactive components that scavenge · OH, density functional theory (DFT) calculations were conducted. Total flavonoid content (TFC) from E. breviscapus was 48.53 mg/g under ideal conditions with PEG2000 mass fraction of 16%, (NH 4 ) 2 SO 4 mass fraction of 14%, ultrasound time of 41 min, and liquid-solid ratio of 35 mL/g. 28 flavonoids have been tentatively identified in E. breviscapus via ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS). Furthermore, EBTF demonstrated moderate hydroxyl radical scavenging capacity, with scavenging rate of 60.68% at 3.9 mg/mL. The 6-OH site of scutellarin was the core active site for scavenging hydroxyl radicals. The findings provide both theoretical and experimental support for the in-depth development of EBTF as a natural antioxidant.