Study On Extraction Of Flavonoids And Antioxidant Activity Of The Extracts From Parnassia Wightiana Wall

Parnassia wightiana W. which belongs to the family Saxifragaceae, genus Parnassia anddistributes in Shaanxi and Gansu Provinces had been widely used as a folk medicine.In thispaper, the optimization of flavonoid extraction was studied in-depth, meanwhile, theantioxidant activity of different solvent extracts from Parnassia wightiana was investigated,the correlation between antioxidant activity and flavonoids content&type was summarized.The total flavonoids extraction volume of Parnassia wightiana was determined byultrasonic extraction; The influence of every factor level on extraction volume of flavonoidsfrom Parnassia wightiana was analyzed through single-factor test, using the extraction volumeof total flavonoids as index. The factor levels included volume fraction of ethanol,dosage ofsolvent,extraction temperature,extraction time, finally the factor levels of orthogonal test weredetermined. On this basis, the optimal conditions of ultrasonic extraction of flavonoids fromParnassia wightiana were determined by orthogonal test.The result of single-factor testshowed that the extraction volume of total flavonoids from Parnassia wightiana was muchhigher when factor levels of volume fraction, dosage of solvent, extraction temperature andextraction time were correspondingly as follows：50%(V/V)-90%(V/V);10-20;35-55℃;30-60min. The result of orthogonal test showed that among the4factors which affected theextraction volume of total flavonoids, the dominative order was：volume fraction of ethanol＞dosage of solvent＞extraction temperature＞extraction time. The optimum conditions forultrasonic extraction of flavonoids were as follows:50%ethanol(V/V),20times dosage ofsolvent,55℃;60min. Under these conditions, the extraction volume of total flavonoids fromParnassia wightiana was up to47.18mg/g.In this study,50%ethanol (in water, v/v) extract from Parnassia wightiana wassuccessively extracted by using3kinds of different solvents to provide chloroform extract(CE), ethyl acetate extract (EAE), n-butanol extract (BE) and water extract (WE). Differentantioxidant assays (O2-, OH, DPPH scavenging activity, reducing power and metalchelating activity) were employed to evaluate the antioxidant activities of four extracts, butylated hydroxytoluene (BHT) was used as the reference antioxidant. The conclusions wereas follows:(1) The compounds with large polarity were the dominative constituents in Parnassiawightiana W. extracts, while the ones with small polarity were less. Flavonoids were mainlyconcentrated in EAE, BE and WE, which crossed a large polarity range.(2) The results of single antioxidant activity assay: WE showed the best scavengingactivity on O2-(IC50value was0.197±0.004), EAE showed the best scavenging activity onOH (IC50value was1.100±0.018), BE possessed the best scavenging activity on DPPH (IC50value was0.322±0.017), EAE showed the strongest reducing power and WE possessed thebest metal chelating ability (IC50value was0.162±0.006). The results of comprehensiveantioxidant activity assay: WE and BE showed the strongest comprehensive antioxidantactivity, in which the scavenging activity on O2-and the metal chelating ability of WE wereeven beyond the reference BHT; On the contrary, the comprehensive antioxidant activity ofCE and EAE were relatively poor.(3) All the extracts showed concentration dependent antioxidant activity and a highcorrelation between content of flavonoids and antioxidant activity. Flavonoids with differentpolarity (different structure) had different antioxidant activity. For hydroxyl radicalscavenging activity, non-polar flavonoids occurring in CE was highest. For superoxide radicalscavenging activity and metal chelating activity, polar flavonoids existing in WE was highest.For DPPH radical scavenging activity, medium-polar flavonoids in BE was highest.