Figure 2
Main lignin structures identified in the eucalypt samples analyzed by heteronuclear single quantum correlation nuclear magnetic resonance (Figures1and3) . A = β-O-4ʹ lignin substructures (including a second S or G unit); Aox = Cα-oxidized β-O-4ʹ lignin substructures; B = phenylcoumarans; C = resinols; D = spirodienones; I = cinnamyl alcohol end-groups; G = guaiacyl units; S = syringyl units; and Sʹ = Cα-oxidized S units (R can be a hydroxyl in carboxylic acids or a lignin side-chain in ketones).