Preparation of Phenolic Acid-sodium Hyaluronate Copolymers and in vitro Antioxidant Activity Assessment
Objective Sodium hyaluronate(HA)was used as the research object to modify it with phenolic acid in order to obtain the molecular structure with better antioxidant activity or even new activity.Methods In this study,5 kinds of phenolic acid-sodium hyaluronate was prepared by free radical-mediated grafting method,and the grafts with the highest grafting degree were selected to optimize the synthesis conditions.Then,grafts structure and physicochemical properties were analyzed.The grafts were characterized by IR,UV,1H NMR,FESEM and TGA spectra.The in vitro antioxidant capacity of grafts was determined by the scavenging ability of DPPH·,ABTS+·and O2-·.Results Among 5 kinds of phenolic acid-sodium hyaluronate,the grafting rate of ferulic acid-sodium hyaluronate copolymer(FA-HA)was highest,which was chosen as experimental sample in the following tests.Firstly,the reaction conditions were investigated and the highest grafting rate was(16.59±0.31)mg/g at the optimal preparation conditions.Then,FA-HA structure and physicochemical properties were analyzed.Data from UV,IR,1H NMR analyses,TGA showed that FA were successfully grafted to HA.Compared with HA,the results of gel permeation chrematography(GPC)showed that the molecular mass distribution of FA-HA copolymer decreased from 34.4 to 31.5 ku,but the uniformity of molecular distribution was improved.FESEM results showed that the structure of copolymer exhibited a closely connected lamellar structure with a relatively smooth surface.TGA results showed that thermal stability of FA-HA had a little decline.The antioxidant performance in vitro results showed that,during 0.25-10 g/L,FA-HA can eliminate(83.76±4.86)％DPPH·,(76.95±5.06)％ABTS+·and(83.08±2.51)％O2-·respectively at 10 g/L.which were higher than that of native HA and FA.Conclusion FA and HA were successfully grafted together by free radical grafting,and the grafted FA-HA had better antioxidant activity in vitro,which provided a theoretical basis for further research and development of phenolic acid-HA grafts.
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