Ultrasonic-assisted extraction process optimization and properties of Hibiseu manihot L.flower
Flavonoids from Hibiseu manihot L.flower were extracted by ultrasonic-assisted extraction method,which was optimized by single factor and orthogonal experiment.The Hibiseu manihot L.flower extracted under the optimal process conditions were then evaluated for its antioxidant activity and safety.The results showed that the optimum extraction process conditions of flavonoids from Hibiseu manihot L.flower were as follows:ultrasonic power 300 W,ethanol volume fraction in ethanol-water 80%,ultrasonic time 35 min,extraction temperature 75℃,solid-liquid ratio(g∶mL)1∶15.Under the above-mentioned optimum extraction process conditions,the maximum extraction rate of flavonoids from Hibiseu manihot L.flower was 89.97%.Flavonoids from Hibiseu manihot L.flower with a mass concentration of 1.00 g/L exhibited the highest scavenging rates on 1,1-diphenyl-2-picrylhydrazyl radical,hydroxyl radical and diammonium 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfpnic acid)free radical,which were 94.81%,95.24%and 82.80%,respectively,with the corresponding half maximal inhibitory mass concentration(IC50)of 106.00,70.06 and 213.80 μg/mL,respectively.Flavonoids from Hibiseu manihot L.flower with a mass concentration of less than 0.4 g/L showed a hemolysis rate of less than 10%on red blood cells,indicating mild irritation,while flavonoids from Hibiseu manihot L.flower with a mass concentration of 1.00 g/L displayed no hemolysis on chick embryo chorioallantoic membrane.