Extraction, antioxidant capacity and identification of Semen Astragali Complanati (Astragalus complanatus R. Br.) phenolics

A study about the ultrasonic extraction, antioxidant capacity and identification of phenolics from Semen Astragali Complanati was undertaken. The optimised extraction condition with an orthogonal experiment design of L9(34) was 50 °C, 30 min and 15:1 (methanol solution:sample, mL:g). An extraction yield of 40.12 ± 1.10 mg gallic acid/g dry seed and the antioxidant capacity of 0.85 ± 0.13 mg dry extract/mg DPPH were obtained with the optimum condition, respectively. For each extraction set, the antioxidant capacity by 2,2-diphenyl-1-picrylhydrazyl radical assay highly correlated to its total phenolic content by Folin–Ciocalteu method. Twelve phenolic components obtained with the optimised extraction procedure were tentatively identified by Ultra Performance Liquid Chromatography coupled with Q-TOF Mass Spectrometer (UPLC-Q-TOF) according to their mass spectrometry, UV/vis spectrometry, and related literature reports. Furthermore, the ultrasonic effect on the particles’ microstructure of Semen Astragali Complanati was also investigated by scanning electron microscopy (SEM) analysis.