Extraction Of Naringin Assisted By Pulsed Electric Field And Its Biological Activity And Metal Complexation

Grapefruit is widely planted in China,mainly for fresh food.Grapefruit peel,as a byproduct of grapefruit processing,is a waste of resources due to low utilization rate.Naringin is a kind of dihydroflavonoid compound,which has many physiological activities such as antiinflammatory and anti-tumor,and widely exists in the peel of grapefruit.In this paper,naringin was extracted from pomelo white capsule by pulse electric field.The influence of single factors such as electric field intensity,pulse number and ethanol concentration on the extraction rate of naringin was studied.The process of naringin extraction by pulse electric field was optimized,and the influence of pulse electric field on the structure and antioxidant activity of naringin was explored.For the first time,the effect of pulse electric field on the physical properties of the complex,such as yield,structure and antioxidant activity,was studied.The main conclusions are as follows.The main factors that affect the extraction efficiency of naringin are electric field intensity,pulse number and ethanol concentration.The order is ethanol concentration > electric field intensity > pulse number.The interaction of electric field intensity and ethanol concentration has the most significant effect on the extraction efficiency of naringin.The optimal extraction conditions determined by response surface were: 29 pulses,4 k V/cm electric field,43% ethanol concentration,40 ?C extraction temperature,90:1 ratio of liquid and material,1.5 h extraction time and 16.79% extraction rate.The DPPH radical scavenging rate of naringin was(22.69 ± 0.08)%,the antioxidant activity of naringin treated by PEF at 30 pulses increased to(29.16 ± 0.08)%.The highest antioxidant activity of naringin was(38.58 ± 0.42)%,which was treated at 4 k V/cm.The results of SEM,IR and NMR showed that the pulse electric field changed the spatial structure of naringin,made naringin crystal smaller,and did not change the chemical structure of naringin.The ability of forming complex between naringin and different metal salts is different,which is naringin-Cu complexes > naringin-Fe complexes.The yield of naringin metal complexes was decreased when treated by pulse electric field,but the effect of different treatment voltage on the yield was different,which was 10 k V/cm > 8 k V/cm > 6 k V/cm.The results of UV and IR showed that the complex group of naringin with metal salt was carbonyl group on benzene ring.Thermogravimetry showed that naringin-Cu complexes had melting point,and the structure of naringin-Fe complexes was mainly amorphous.Pulse electric field treatment did not affect the binding sites and the crystal state of the complexes.The thermal stability of naringin decreased after the formation of complex,which is naringin-Cu complexes > naringin-Fe complexes > naringin.The thermal stability of naringin was improved by electric field treatment,and the treatment conditions were 6 k V/cm > 8 k V/cm > 10 k V/cm > untreated complexes.The inhibition rates of naringin and its metal complexes on DPPH radicals were: naringinFe complexes > naringin > naringin-Cu complexes.Pulse electric field treatment can enhance the ability of the complex to inhibit DPPH radicals,and the treatment conditions are 6 k V/cm > 8 k V/cm > 10 k V/cm > untreated complexes.The inhibition ability of naringin and its metal complexes to ?-amylase was successively as follows: naringin-Cu complexes > naringin > naringin-Fe complexes.The inhibition activity of naringin-Cu complexes to amylase decreased after electric field treatment,while the inhibition activity of naringin-Fe complexes to amylase increased,and the complexation reaction between naringin and metal was affected by electric field treatment.The inhibition of naringin and its metal complexes on lipase was as follows: naringin-Fe complexes > naringin-Cu complexes > naringin.The ability of naringin-Cu complexes and iron complexes to inhibit lipase activity was enhanced by pulse electric field treatment,and increased first and then decreased with the increase of treatment voltage.However,naringin-Fe complexes can activate trypsin.The effect of electric field treatment on trypsin activity will move to the inhibition direction.