Sunday, May 4, 2008
4-09

Antioxidant Activity of Low-molecular-weight Lignin Fraction from Organosolv Pretreatment of Wood for Ethanol Production

Xuejun Pan1, Li Shuai1, and J. Y. Zhu2. (1) Biological Systems Engineering, University of Wisconsin, 460 Henry Mall, Madison, WI 53706, (2) USDA Forest Service, Forest Products Laboratory, One Gifford Pinchot Dr, Madison, WI 53726

Like other naturally occurring polyphenols, lignin possesses antioxidant activity. The radical scavenging capacity of lignin is dependent on the source and preparation method, specifically on the structural features of the lignin. Ethanol organosolv lignin samples were prepared from lodgepole pine under varied conditions (temperature, reaction time, ethanol concentration and catalyst dosage), which include water-insoluble organosolv lignin (high molecular weight fraction) and water-soluble lignin (low molecular weight fraction). Functional groups and molecular weight of the lignin samples were determined by means of NMR and GPC. Antioxidant activity of the lignin preparations was evaluated using DPPH (1,1-Diphenyl-2-picrylhydrazyl) method. Results indicated that the radical scavenging capacity of lignins was dependent on functional groups and molecular weight. The lignin with more phenolic hydroxyl groups, low molecular weight and narrow polydispersity showed high antioxidant activity. Pretreatment conditions affected the functional groups and molecular weight of the extracted organosolv ethanol lignins, and thereby influenced the antioxidant activity of the lignins. In general, the lignins prepared at elevated temperature, longer reaction time, increased catalyst, and diluted ethanol possessed high antioxidant activity.

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