Table 5 Lignin structural characteristics from integration of 13 C- 1 H correlation signals in the HSQC spectra the lignin fractions
| Â | Control | F4-a | F4-b |
|---|---|---|---|
Lignin interunit linkages (%) | |||
β-O-4′ aryl ether (A) | 80.7 | 80.1 | 79.0 |
Resinol substructures (B) | 16.1 | 17.0 | 17.4 |
Phenylcoumaran (C) | 3.2 | 2.9 | 3.6 |
Lignin aromatic units | |||
S/G ratio | 1.7 | 2.0 | 2.1 |
S/S’ ratio | 3.8 | 6.9 | 7.0 |