This study aimed to devise an integrated green surfactant and circulating ultrasound coupling extraction (GSCUE) approach for extracting the total flavonoids from Cynanchum auriculatum leaves. Single-factor optimization combined with a Box–Behnken design was used to determine the optimal technological conditions, which included an APG0814/MES amount of 5 % (w/v), extraction temperature of 46 °C, ultrasound irradiation power of 509 W, liquid–solid ratio of 30 mL/g, mixing speed of 1000 r/min, and extraction time of 50 min. Under these conditions, the extraction yield of the total flavonoids reached 7.83 mg/g. The HPLC-MS was applied to identify the flavonoid compositions in Cynanchum auriculatum leaves extract. The results showed that flavonoid composition included Gardenin B, Luteolin, Kaempferol, Quercetin, 4′-Methoxy-7-O-beta-D-glucopyranosyl-8,3′-dihydroxyflavanone, Astragalin, Spiraeoside, Rutin, and Kaempferol 3-gentiobioside. Further, to investigate the GSCUE mechanism, plant samples before and after extraction were analyzed by fourier transform infrared spectroscopy, scanning electron microscopy, and contact angle analysis. The results indicate that the functional groups, surface microstructure, and surface wettability of the plant samples all affect the yield of the target active ingredients. The hydrophilic group content on the plant sample surface after GSCUE treatment was higher compared to the case of the untreated samples. Additionally, there was evidence of surface structural collapse and shrinkage, increased surface roughness, and a decreased contact angle due to GSCUE treatment. These results highlight the greater surface wettability of the plant samples, faster solvent penetration, and an effective increase in the total flavonoid yield, indicating the synergistic effect of combining ultrasound with green surfactants for total flavonoid extraction. Overall, GSCUE technology provided a sustainable and efficient approach for extracting the total flavonoids from plant materials.
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