Optimization of Ethanol Extraction Process for Active Components from Broussonetia papyrifera Root Bark and Its Antioxidant Activity

In this study, single factor experiments were employed to determine the effects of various factors on yields of total flavonoids and polyphenols from Broussonetia papyrifera root bark. Then Box-Behnken design and response surface methodology were used to optimize the ethanol reflux extraction process using the Design-Expert 11 software. Moreover, the antioxidant activity of the ethanol extract of Broussonetia papyrifera root bark was evaluated by determining the scavenging capacity of DPPH·, ABTS⁺·, and the hydroxyl free radical, as well as the total reducing power. Results showed that the optimal conditions were as follows: Extraction temperature 75 ℃, extraction time 117 min, solid-liquid ratio 1:16 g/mL, and ethanol concentration 70%. Under these conditions, the experimental extraction yield values of total flavonoids and polyphenols from Broussonetia papyrifera root bark were 23.93±0.30 mg/g and 14.69±0.56 mg/g, respectively, which was not significantly different in comparison to predicted values. The IC₅₀ values of scavenging rates on DPPH·, ABTS⁺·, and the hydroxyl free radical were 5.256 μg/mL, 0.259 mg/mL, and 0.310 mg/mL, respectively, and the scavenging rates showed a certain dose-effect relationship with the sample concentration. In addition, the total reducing power of 1.0 mg/mL ethanol extract of the root bark was 1.484±0.062. These results indicated that this optimization test was effective and feasible, and the ethanol extract of Broussonetia papyrifera root bark had good antioxidant activity in vitro. The present study provides supplement information for the comprehensive utilization of Broussonetia papyrifera in food and medicine ingredients.