Optimization for extraction process of flavonoids from Potentilla fruticosa L. by response surface method and the analysis of its antioxidant and hypoglycemic activities

【Objective】The ultrasonic extraction conditions of flavonoids from Potentilla fruticosa L. were optimized, the types and contents of flavonoids were detected, and their antioxidant and hypoglycemic capacities were analyzed, in order to provide technical support for comprehensive utilization of P. fruticosa L.【Method】The single factor method and the response surface methodology(RSM) were employed to optimize the main parameters of ultrasonic extraction of flavonoids from P. fruticosa L.,with extraction yield as the index. Multiple chromatographic columns were used for the separation and purification of the flavonoid compounds, and the antioxidant capacity and hypoglycemic capacity of these compounds were compared.【Result】The significant order of the four factors on the extraction yield of flavonoids was as follows:solvent/solid ratio>ultrasonic time>volume fraction of ethanol>ultrasonic power. The regression equation established was as follows:Y=37.84+14.48A+14.93B+3.02C+9.38D-0.03AB-0.66AC-0.01AD-0.01BD-0.01CD-14.71A²-11.25B²- 16.96C²-12.89D²(Y represented extraction rate of flavonoids; A, B, C and D represented liquid-solid ratio, ethanol volume fraction, ultrasonic power and ultrasonic time, respectively). The optimal extraction conditions were as follows:liquid-solid ratio of 39.78:1 (mL/g), ethanol volume fraction of 65.47%, ultrasonic power of 390.98 W and ultrasonic time of 49.55 min. Under these conditions, the extraction yield of flavonoids was 47.59 mg/g. Eight flavonoids were found in the extract of P. fruticosa L., among which the most abundant was quercetin-7-O-β-D-glucuronide(10.90 mg/g). Naringenin had the lowest scavenging yield of DPPH free radical,which was only 5.0%, while the scavenging yields of seven other compounds were greater than 50.0%, indicating good antioxidant activities. The glucose consumption yield of flavonoid compounds in P. fruticosa L. were higher than that of DMSO,and the glucose consumption yields of(+) -catechin, quercetin-3-O-β-D-glucuronide and quercetin-3-vicianoside reached more than 19.5%,suggesting their good hypoglycemic activities.【Conclusion】The optimized ultrasonic extraction process of flavonoids by RSM is feasible and the established regression equation has high accuracy. The multiple chromatographic columns can be used for the separation and purification of the flavonoids in P. fruticosa L. All components except naringenin have obvious antioxidant activity, and all components have a certain hypoglycemic activity. P. fruticosa L. can be developed as a natural source of antioxidants and hypoglycemic agents in food, medicine and other fields.