Optimization of ultrasonic-assisted extraction of total flavonoids from pomegranate root bark and thear nitrosation inhibition activity

The ultrasonic-assisted extraction conditions of total flavonoids from pomegranate root bark were studied. Single factor test and Box-Behnken experimental design were used to optimize the extraction process employing total flavonoids yield as the response,and ethanol concentration,solid/liquid ratio,ultrasonic power and ultrasonic time were used as independent variables,and the nitrite scavenging activity and nitrosamine synthesis inhibiting activity were tested. Results showed that under the following conditions:Ethanol concentration of 63%,solid/liquid ratio of 1∶22 g/mL,ultrasonic power of 270 W and ultrasonic time of 34 min,the yield of total flavonoids was 2.81%,close to predicted value. The total flavonoids from pomegranate root bark had a strong nitrite scavenging activity and nitrosamine synthesis inhibiting activity. At the concentration of 3.6 μg/mL,the total flavonoids exhibited a maximum sodium nitrite scavenging rate of 64.5% and the effect of IC₅₀=2.408 μg/mL.At the same time,the total flavonoids exhibited a maximum nitrosamine synthesis inhibiting rate of 71.9% at the effect of IC₅₀=2.345 μg/mL. There was a dose-response relationship between the total flavonoids from pomegranate root bark and the nitrite scavenging activity and nitrosamine synthesis inhibiting activity in the range of 0.12~3.6 μg/mL of concentration. This method could provide a scientific basis for the extraction and application of total flavonoids from pomegranate root bark.