Preparation And Properties Of Multifunctional Hydroxycnnamic Acid Arabinoxylan Esters

In this paper,arabinoxylan?CAX?was extracted from corn bran according to alkali-hydrogen peroxide method,and it was modified with hydroxycinnamic acid?HA??including ferulic acid?FA?,p-coumaric acid?p-CA?,sinapic acid?SA?and caffeic acid?CA??by esterification to generate hydroxycinnamic acidarabinoxylan ester?HA-CAX?,i.e.arabinoxylan p-coumaric acid ester?p-CA-CAX?,arabinoxylan ferulic acid ester?FA-CAX?,arabinoxylan sinapic acid ester?SA-CAX?,and arabinoxylan caffeic acid ester?CA-CAX?).The structure of HA-CAX was characterized by FT-IR,NMR and the degree of substitution?DS?was determined by HPLC,and the results indicated that HA had been grafted on CAX successfully.The physical-chemical properties,especially,aqueous solution behavior of HA-CAX were investigated by UV absorption spectroscopy,thermogravimetric,surface tension meter,fluorescence spectroscopy,light scattering,scanning electron microscope and rheological measurement.CAX has no UV absorption,whereas HA-CAX exhibits good UV absorption coefficient from 250 nm to 350 nm with fine photostability.The surface tension of CAX aqueous solution was about 71 mN/m,the surface tension of HA-CAX aqueous solution was significantantly lower than that of CAX,and it decreased with the increasing HA content.Fluorescent molecular probe was used to detecte the intermolecular hydrophobic association of CAX and HA-CAX aqueous solution,the critical associating concentration?CAC?of CAX was about 8.34 mg/mL,and the CAC of HA-CAX decreases with increasing substituting degree.The HA-CAX was used to prepare emulsion as an emulsifer and the emulsion properties were investigated.The droplet size of HA-CAX stabilized emulsion were smaller than that of CAX stabilized emulsion,and the stability of emulsion stabilized by HA-CAX was superior to that by stabilized CAX.Laser light scattering result indicates that CAX is like a random coil chain but HA-CAX chain agreagetes to non-draining sphere.This result has been confirmed by SEM result of HA-CAX.The viscosity of HA-CAX increases significantly compared with CAX at the same concentration and shear rate,and HA-CAX exhibites gel behavior.The order of solution viscosity was SA-CAX>CA-CAX>FA-CAX>p-CA-CAX,and SA-CAX shows the trongest gel behavior.The antioxidative potential of HA-CAX was evaluated using DPPH and hydroxyl radicals scavenging,Fe²⁺chelating effect,antioxidant activity in MeLo emulsion,inhibiting lipid peroxidation,and oxygen radical scavenging capacity?ORAC?.Compared with CAX,the HA-CAX exhibites superior antioxidant activitiesin vitro,the antioxidant of each HA-CAX increases with the HA content,the order is CA-CAX>SA-CAX>FA-CAX>p-CA-CAX.The HA-CAX and CAX are non-toxic at the concentration of 0.25-2.5 mg/mL,as is used to three kinds of cells?HepG2,EC and HSF?.Two cell models,including cellular antioxidant activity?CAA?assay and H₂O₂-induced oxidative damage,the results of two methods were identical,the order of the antioxidant was CA-CAX>SA-CAX>FA-CAX>p-CA-CAX,and the antioxidant ability of HA-CAX increases with the increasing of HA content.H₂O₂-induced HSF causes late apoptosis,and HA-CAX can protect it.