Antioxidation And Bacteriostasis Activity Of Different Extraction Parts In The Alcohol Extract Of Sunflower Stalk Pulp

Sunflower is an economic crop widely cultivated in China.Currently,a large number of studies have focused on sunflower,but there is less research on the stalk pulp part.Alcohol extract of sunflower stalk pulp was produced using ultrasonic assisted extraction.Next,with three different polar solvent,we got petroleum ether extraction part(PE),ethyl acetate extraction part(EE)and n-butanol extraction part(BE),respectively.Results showed that all three extracts contain phenols and flavonoids,both of which in EE were the highest,with the components were 1.60±0.10(mg GA/g)and 20.50± 1.55(mg RT/g),respectively,followed by PE,and BE minimum.The in vitro antioxidant capacity results showed that all extracts were have DPPH and ABTS radical scavenging capacity and total reduction ability,antioxidant activity enhanced with the increase of concentration,in which the highest antioxidant capacity of EE,with DPPH radical scavenging activity IC50=2.56±0.10 mg/mL,ABTS radical scavenging activity 52.00±1.97 μmoL Trolox/g,and total reduction ability 120.57±0.74 μmoL Trolox/g,respectively.The correlation analysis results showed that there was a significant correlation between antioxidant capacity of the extracts and the content of total phenols and flavonoids(P<0.01).Inhibition zone,minimal inhibitory concentration(MIC)and half inhibitory concentration(IC50)toxwards Staphylococcus aureus,Escherichia coli,Bacillus subtilis and Serratia marcescens were measured using an agar dilution method.All of PE,EE and BE exhibited antibacterial activity against the tested bacteria with the EE possess largest antibacterial efficacy.Correlation analysis showed that the inhibiting proliferation ability of three extracts to four bacteria have significant correlation with total phenols content(P<0.01).We also found that there was a positive correlation between inhibition of Escherichia coli,Staphylococcus aureus and Serratia marcescens proliferation and flavonoids content(P<0.05).However,there was no significant correlation of the inhibition to Bacillus subtilis with flavonoids content.It is speculated that the total phenols and total flavonoids in the medulla of sunflower are the material basis of their inhibitory action.The inhibitory mechanism of EE towards Staphylococcus aureus and Escherichia coli were assayed using scanning electron microscope,conductivity and AKP value of bacteria suspension,extracellular soluble protein content of bacteria suspension,fluorescence microscopy and fluorescence spectrophotometer methods.Results showed that EE could lead to morphological changes of the bacteria.EE could destroyed the cell membrane and cell wall of the bacteria,and release the charged ions,proteins and AKP in the cell.EE also could inhibit the replication of bacterial genetic material(DNA)and ultimately inhibited bacterial reproduction.