CORRELATION OF LIGNIN STRUCTURE TO ITS ANTIOXIDANT ACTIVITY

Abstract. The structure of lignin obtained after pretreatment of lignocellulosic biomass determines its use for producing value-added products. One attractive application of the lignin is for use as an antioxidant. In this study, the lignin obtained from ozone and soaking aqueous ammonia pretreatment of wheat straw was characterized in order to reveal its primary structural properties involved in antioxidant activity. The characterization results showed that specific esters bonds in wheat straw lignin such as -C I² -COO-arabinose and –CI³OO-C- were dissociated during the pretreatment, which resulted in a reduced molecular weight and selective release of derivatives from hydroxycinnamic acid such as ferulic acid and I-coumaric acid units. The combination of these factors led to the extracted lignin having a comparable antioxidant activity to that of the currently used industrial antioxidants. The percent inhibition effect was observed to be in the following order: guaiacol > butylated hydroxytoluene > ferulic acid > lignin (86.9±0.34).