Table 4.
Lignin and LCC linkage characteristics from the integration of quantitative 13C and 2D HSQC NMR spectra.
| Range (ppm) | Assignment | Amount | |
|---|---|---|---|
| ML | FZ | ||
| Lignin characteristic 1 | |||
| 199–196 | Cα = O except G′ | 0.07 | 0.05 |
| 196–193 | C = O in Cα = O/β-O-4′ (A′), F, J | 0.08 | 0.07 |
| 193–190 | Ar-CHO | 0.07 | 0.07 |
| 182–179 | C4 in F (β-1′) | 0.03 | 0.03 |
| 175–168.5 | aliphatic COOR | 0.07 | 0.09 |
| 168.5–166 | conjugated COOR | 0.02 | 0.03 |
| 159–151 | Cα in J, C3, 6 in F, C4 in conjugated CO/COOR etherified units | 0.29 | 0.25 |
| 144.5–142.5 | C3 in B (β-β′) | 0.20 | 0.25 |
| 57–54 | –OCH3, C1 in F | 1.05 | 1.08 |
| 54–52 | Cβ in B and C (β-β′, β-5′) | 0.18 | 0.16 |
| Clusters 1 | |||
| 163–142 | aromatic C-O | 1.85 | 1.79 |
| 142–125 | aromatic C-C | 1.52 | 1.56 |
| 125–102 | aromatic C-H | 2.62 | 2.67 |
| 90–58 | Alk-O- | 2.23 | 2.36 |
| 90–77 | Alk-O-Ar, α-O-Alk | 0.83 | 0.83 |
| 77–65 | γ-O-Alk, secondary OH | 0.68 | 0.75 |
| Interunit linkages and structural units 2 | |||
| 111.0/6.98 | guaiacyl units (G) | 99 | 99 |
| 128.0/7.20 | p-hydroxyphenyl units (H) | 1 | 1 |
| 71.2/4.74 | β-O-4′ alkyl ether linkages (A′) | 40 | 41 |
| 87.0/5.45 | phenylcoumaran substructures (B) | 12 | 14 |
| 84.9/4.63 | resinol substructures (C) | 3 | 4 |
| 83.3/4.83 | dibenzodioxocin substructures (D) | 1 | 2 |
| 81.4/5.03 | spirodienone substructures (F) | <1 | <1 |
| LCC linkages 3 | |||
| 104.0–98.0/5.30–4.50 | PhGlc | 0.035 | 0.027 |
| 82.5–80.0/5.30–4.30 | BE | 0.008 | 0.008 |
| 66.0–62.0/4.50–4.00 | Est | 0.026 | 0.039 |
1 Quantified according to the method described by Capanema et al. [13]; results expressed per Ar; 2 Molar percentages (H + G = 100); Interunit linkages molar contents as percentages of lignin content; 3 The sum of LCC γ-ester and γ-acylated β-O-4′ aryl ether substructures (A′); results expressed per Ar.