Optimization of Extraction Process and Antioxidant Activity of Ligusticum chuanxiong Protein by Response Surface Methodology

The aim of this study was to optimize the extraction process of Ligusticum chuanxiong protein (LCP) and to investigate its antioxidant activity. Based on single factor experiment, Box-Behnken response surface methodology was used to optimize the extraction process of LCP, with solid-liquid ratio, extraction time, extraction solvent pH as the factors, and extraction rate of LCP as the index. The molecular weight range of LCP was determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The isoelectric point (pI) and solubility of LCP were determined, and the antioxidant activity of LCP was investigated. The results showed that the optimal extraction conditions were solid-liquid ratio of 1:15 (g/mL), extraction time of 1.5 h and pH of 6. Under the optimized conditions, the extraction yield of LCP was （2.36%±0.13%）, and the measured value was close to the theoretical value, indicating that the mathematical model could be used to optimize the extraction process of LCP. Under the optimal conditions, the molecular weight of the extracted LCP was 17~48 kDa, the isoelectric point was 3.88, the solubility was 96% at pH8. The IC₅₀ of hydroxyl radical scavenging activity was 1.18 mg/mL, the IC₅₀ of superoxide anion radical scavenging activity was 0.57 mg/mL, and the IC₅₀ of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was 1.31 mg/mL. LCP extracted by this method has good antioxidant activity, which can provide experimental ideas for further research and development of LCP antioxidant activity.