Optimization of Extraction Process of Melanin from Zanthoxylum bungeanum Seeds of Tianshui and Its Antioxidant Activity in Vitro

Single factor experiments combined with response surface methodology (RSM) was used to optimize the extraction process of melanin from Zanthoxylum bungeanum seeds of Tianshui and evaluated its antioxidant activity. The results showed that the optimal extraction conditions were determined as follows: NaOH concentration was 1.11 mol/L, extraction temperature was 59 ℃, solid-liquid ratio was 1:23 g/mL, extraction time was 2 h. Under the optimal process parameters, the yield of melanin from Zanthoxylum bungeanum seeds of Tianshui was 7.60%±0.05%, which was close to the predicted value (7.75%) of the model, and the relative error was 0.66%. It showed that the regression term and the fitting degree of the model were good, and the optimized process conditions were feasible. The results of antioxidant experiments in vitro showed that the scavenging rates of melanin from Zanthoxylum bungeanum seeds on hydroxyl radical (·OH), 1,1-diphenyl-2-picrylhydrazyl (DPPH·), 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS⁺·) reached 66.07%±0.96%, 61.27%±0.97%, 62.19%±0.83%, respectively, which indicated that melanin from Zanthoxylum bungeanum seeds of Tianshui had good scavenging activity on·OH, DPPH· and ABTS⁺·.