Correlations of physicochemical properties of organosolv lignins from Broussonetia papyrifera with their antioxidant activities

To understand the influence of lignin characteristics on their antioxidant activities, lignin was isolated Broussonetia papyrifera by organosolv pretreatment under different temperatures. The physicochemical features of the lignins were investigated by FT-IR, GPC, 31P NMR and 2D HSQC NMR analyses. An increase of organosolv pretreatment temperature resulted in a decrease of Mw and an increase of phenolic hydroxyl groups content in the isolated lignin. The lignins extracted under high organosolv pretreatment temperature showed high antioxidant activity according to the IC50 determined by DPPH and ABTS. The correlations between physicochemical properties of organosolv lignins and their antioxidant activities were studied. The contents of phenolic hydroxyl groups, especially from syringyl and guaiacyl,and double bonds in the Cα position had positive effects on the antioxidant activity of the lignins. On the other hand, Mw and aliphatic hydroxyl group of the lignins exhibited negative correlations with the antioxidant activity