Table 4 Assignments of main lignin and polysaccharide 13 C- 1 H correlation signals in the HSQC spectra the lignin fractions
Labels | δC/δH(ppm) | Assignment |
|---|---|---|
C β | 53.1/3.47 | Cβ-Hβ in phenylcoumaran substructures (C) |
B β | 53.4/3.06 | Cβ-Hβ in resinol substructures (B) |
-OMe | 55.6/3.72 | C-H in methoxyls (MeO) |
A γ | 60.0/3.40-3.69 | Cγ-Hγ in β-O-4′ substructures (A) |
F γ | 61.3/4.09 | Cγ-Hγ in p-hydroxycinnamyl alcohol end groups (F) |
C γ | 63.2/3.70 | Cγ-Hγ in phenylcoumaran substructures (C) |
B γ | 71.7/3.81 and 4.18 | Cγ-Hγ in resinol substructures (B) |
A α | 71.8/4.85 | Cα-Hα in β-O-4′ substructures (A) |
A β(G) | 84.1/4.27 | Cβ-Hβ in β-O-4′ substructures linked to a G unit (A) |
B α | 85.1/4.66 | Cα-Hα in resinol substructures (B) |
C α | 86.8/5.45 | Cα-Hα in phenylcoumaran substructures (C) |
A β(S) | 86.1/4.11 | Cβ-Hβ in β-O-4′ substructures linked to a S unit (A) |
S 2,6 | 103.9/6.69 | C2,6-H2,6 in etherified syringyl units (S) |
S’ 2,6 | 106.2/7.19 | C2,6-H2,6 in oxidized (Cα = O) phenolic syringyl units (S’) |
G 2 | 111.1/6.96 | C2-H2 in guaiacyl units (G) |
G 5 /G 6 | 115.0/6.64 and 6.91; 119.0/, 6.82 | C5-H5 and C6-H6 in guaiacyl units (G) |