Figure 2

Selected hardwood lignin structures: (a) methoxy group, (b) β -O-4 ether, (c) β -5/ α - O -4 phenyl-coumaran, and (d) spirodienone.
Selected hardwood lignin structures: (a) methoxy group, (b) β -O-4 ether, (c) β -5/ α - O -4 phenyl-coumaran, and (d) spirodienone.