Antioxidant Activity Optimization Of Masson Lignin And Its Application In Varnish

Lignin,the second most abundant and unique aromatic polymer in plants,is a natural polyphenolic antioxidant as well as a broad-spectrum sun blocker.Based on these properties,lignin applied in polymers,foods,cosmetics,and pharmaceuticals attracts considerable attention.However,the deep color,irregular agglomeration and poor compatibility inhibit its antioxidant efficiency.In this work,two methods to optimize the antioxidant properties of organosolv lignin(OL)extracted from masson were proposed.Furthermore,OL and optimized derivatives were applied in varnish and their UV-blocking and antioxidant performance were investigated.OL was extracted from masson wood by ethanol water solution at high temperature.The free radical scavenging ability of OL at different concentrations was analyzed by DPPH method.The DPPH radical scavenging rate of OL was much higher than that of industrial antioxidant 1010,but it was slightly lower than that of natural antioxidant quercetin(Qc).To optimize the antioxidant property of OL,Qc was applied to blend with OL to improve its antioxidant performance,and the free radical scavenging ability of OL/Qc mixture at different ratio were analyzed by DPPH method.It was found that OL/Qc had synergistic antioxidant effect at low concentration,and the best ratio of OL and Qc was 4:1.UV irradiation had the most obvious impact on the OL/Qc mixture antioxidant activity compared with influences such as acid and alkali environments.The synergistic antioxidation against UV irradiation of the mixture was also observed.After UV irradiation for 4 h,the scavenging amount of DPPH radicals by OL and Qc both reduced significantly,while their mixtures still present a high scavenging ability.The synergism mechanism was investigated by fluorescence,nuclear magnetic resonance and UV-vis spectra.The results show that Qc molecules could be inserted into OL macromolecules to weaken the aggregation of OL,thus OL/Qc complexes were formed.Macromolecular self-assembling method was used to improve the antioxidant activity of OL.OL was self-assembled into uniform colloidal spheres(OLCS)in acetone-water solution and their morphology and antioxidant property were characterized.DPPH test show that the antioxidant activity of OLCS was better than that of OL.Then,both OL and OLCS were blended with varnish for better UV-blocking and antioxidant performance.The results showed that OL and OLCS effectively improved the UV absorbing and antioxidant properties of varnish.Due to the higher surface area and better compatibility,the UV-blocking effect and antioxidant activity of 1 wt% OLCS modified varnish were better than that of OL midified varnish.The antioxidant properties of the OLCS modified varnish were increased by 81.4% compared with the OL midified varnish,and the antioxidant effect was 97% higher than that of the original varnish.Both OL and OLCS had little influence on the appearance and hardness of varnish under such dosage.