TABLE 3.
Assignments of the lignin 1H/13C correlation signals in the 2D HSQC spectra from the whole cell walls of rice husks and straw and their isolated MWLs (in DMSO–d6).
| Label | δC/δH (ppm) | Assignment |
| C′β | 49.7/2.58 | Cβ/Hβ in γ-acylated β–β′ tetrahydrofurans (C′) |
| Bβ | 53.1/3.41 | Cβ/Hβ in β–5′ phenylcoumarans (B) |
| Cβ | 53.6/3.07 | Cβ/Hβ in β–β′ resinols (C) |
| −OCH3 | 55.6/3.73 | C/H in methoxyls |
| Aγ | 59.4/3.20, 3.56 | Cγ/Hγ in normal (γ-hydroxylated) β–O–4′ substructures (A) |
| Fβ | 59.3/2.76 | Cβ/Hβ in spirodienones (F) |
| Iγ | 61.5/4.09 | Cγ/Hγ in cinnamyl alcohol end–groups (I) |
| Bγ | 62.6/3.68 | Cγ/Hγ in β–5′ phenylcoumarans (B) |
| A′γ | 62.7/3.83, 4.30 | Cγ/Hγ in γ-acylated β–O–4′ substructures (A′) |
| I′γ (pCA) | 64.0/4.77 | Cγ/Hγ in γ-p-coumaroylated cinnamyl alcohol end–groups (I′) |
| Cγ | 71.0/3.82, 4.18 | Cγ/Hγ in β–β′ resinols (C) |
| Aα | 71.8/4.87 | Cα/Hα in β–O–4′ substructures (A) |
| A′β(G) | 81.2/4.64 | Cβ/Hβ in γ-acylated β–O–4′ alkyl-aryl ethers (A′) linked to a G unit |
| Fα | 81.2/5.02 | Cα/Hα in spirodienones (F) |
| C′α | 82.6/5.00 | Cα/Hα in γ-acylated β–β′ tetrahydrofurans (C′) |
| A′β(S) | 83.0/4.33 | Cβ/Hβ in γ-acylated β–O–4′ alkyl-aryl ethers (A′) linked to a S unit |
| Dα | 83.3/4.82 | Cα/Hα in 5–5′ dibenzodioxocins (D) |
| Aβ(G) | 83.9/4.28 | Cβ/Hβ in β–O–4′ alkyl-aryl ethers (A) linked to a G unit |
| Cα | 84.9/4.67 | Cα/Hα in β–β′ resinols (C) |
| Fα′ | 85.2/4.72 | Cα′/Hα′ in spirodienones (F) |
| Dβ | 85.4/3.86 | Cβ/Hβ in 5–5′ dibenzodioxocins (D) |
| Aβ(S) | 85.9/4.12 | Cβ/Hβ in β–O–4′ alkyl-aryl ethers (A) linked to a S unit |
| Aβ(T) | 86.1/4.31 | Cβ/Hβ in β–O–4′ substructures (A) linked to tricin |
| Bα | 86.9/5.47 | Cα/Hα in phenylcoumarans (B) |
| T8 | 94.0/6.56 | C8/H8 in tricin (T) |
| T6 | 98.7/6.22 | C6/H6 in tricin (T) |
| S2,6 | 103.8/6.69 | C2/H2 and C6/H6 in etherified syringyl units (S) |
| T2′,6′ | 103.9/7.28 | C2′/H2′ and C6′/H6′ in tricin (T) |
| T3 | 104.6/7.02 | C3/H3 in tricin (T) |
| G2 | 110.9/7.00 | C2/H2 in guaiacyl units (G) |
| FA2 | 111.0/7.32 | C2/H2 in ferulates (FA) |
| pCA8/FA8 | 113.5/6.30 | C8/H8 in p–coumarates (pCA) and ferulates (FA) |
| H3,5 | 114.5/6.68 | C3/H3 and C5/H5 in p-hydroxyphenyl units (H) |
| G5/G6 | 114.9/6.74, 6.94 | C5/H5 and C6/H6 in guaiacyl units (G) |
| FA5 | 115.4/6.88 | C5/H5 in ferulates (FA) |
| pCA3,5 | 115.5/6.77 | C3/H3 and C5/H5 in p-coumarates (pCA) |
| FA6 | 123.3/7.10 | C6/H6 in ferulates (FA) |
| J8 | 126.3/6.76 | C8/H8 in cinnamaldehyde end-groups (J) |
| H2,6 | 127.6/7.17 | C2/H2 and C6/H6 in p-hydroxyphenyl units (H) |
| Iβ | 128.2/6.21 | Cβ/Hβ in cinnamyl alcohol end–groups (I) |
| Iα | 128.4/6.44 | Cα/Hα in cinnamyl alcohol end–groups (I) |
| pCA2,6 | 129.9/7.45 | C2/H2 and C6/H6 in p-coumarates (pCA) |
| pCA7/FA7 | 144.4/7.41 | C7/H7 in p–coumarates (pCA) and ferulates (FA) |