FIGURE 5.

Main structures identified in the NMR spectra of the lignins of rice husks and straw. A, β–O–4′ alkyl-aryl ethers; A′, β–O–4′ alkyl-aryl ethers acylated at the γ-OH; B, phenylcoumarans; C, resinols; C′, tetrahydrofurans acylated at the γ-OH; D, dibenzodioxocins; F, spirodienones; I, p-hydroxycinnamyl alcohol end-groups; I′, p-hydroxycinnamyl alcohol end-groups acylated at the γ-OH; J, cinnamaldehyde end-groups; pCA, p-coumarates; FA, ferulates; H, p-hydroxyphenyl units; G, guaiacyl units; S, syringyl units; S′, Cα-oxidized S-units; T, tricin. The structures are colored in order to match the signals in the HSQC spectra of Figures 3, 4.