Optimization of ultrasound, microwave and Soxhlet extraction of flavonoids from Millettia speciosa Champ. and evaluation of antioxidant activities in vitro

Ultrasonic-assisted extraction (UAE) and microwave-assisted extraction (MAE) were developed to extract flavonoids antioxidants from the root of Millettia speciosa ( Millettia speciosa Champ.). The optimal experimental parameters for antioxidant extraction from M. speciosa Champ. were measured using single-factor experimentation combined with response surface methodology (RSM). Final extraction rate (FER) of flavonoids assay was used to quantify antioxidant compounds. Then, 2,2ˊ-diphenyl-1-picryhydrazyl (DPPH) scavenging capacity, 2,2ˊ-azino-bis(3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) scavenging capacity and ferric reducing antioxidant power (FRAP) were used to determine the antioxidant capacities of extract. Besides, UAE and MAE were compared with conventional Soxhlet extraction (CSE) and M. speciosa Champ. powders were observed by scanning electronic microscopy to analyze the damage of cell structure caused by different extraction methods. The results showed that UAE was the optimal extraction method to extract flavonoids compounds from M. speciosa Champ. and the optimized UAE conditions of flavonoids was as follows: ethanol, 80%, temperature, 40 °C and ultrasonic power, 500 W. This paper provided useful information to utilize the resource of Chinese herbal medicine and manifest the great antioxidant activities of M. speciosa Champ., and the optimized UAE conditions of flavonoids from M. speciosa Champ. could be used in industrial production.