Table 3.
Relative abundances of the structures found in the HSQC spectra of DL for the species of Cactaceae studied, corresponding to the main inter-unit linkages and the main aromatic units of lignin.
| Pereskioideae | Opuntioideae | Cactoideae | ||
|---|---|---|---|---|
| P. lychnidiflora | O. streptacantha | F. hamatacanthus | P. chrysacanthus | |
| LIGNIN INTER-UNIT LINKAGES (%) | ||||
| β-O-4′ (A) | 80 | 85 | 67 | 70 |
| α-Oxidized β-O-4′ (Aox) | 1 | 3 | 0 | 0 |
| Phenylcoumaran (B) | 6 | 1 | 0 | 7 |
| Resinol (C)a | 13 | 10 | 26 (8) | 22 |
| Dibenzodioxocin (D) | 0 | 0 | 1 | 1 |
| α-O-4′ (E) | 0 | 0 | 1 | 0 |
| Spirodienone (F) | 0 | 0 | 5 | 0 |
| LIGNIN SIDE-CHAIN γ-ACYLATION (%) | ||||
| γ-Acylated β-O-4′ (A') | 0 | 0 | 4 | 5 |
| LIGNIN END-GROUPS (%)b | ||||
| Cinnamyl alcohol end-groups (I) | 0 | 0 | 2 | 0 |
| Cinnamaldehyde end-groups (J) | 2 | 4 | 2 | 2 |
| LIGNIN AROMATIC UNITS (%)c | ||||
| G | 38 (27) | 31 (23) | 6 (3) | 54 (44) |
| S | 62 (73) | 69 (77) | 94 (97) | 46 (56) |
| S/G Ratio | 1.6 (2.7) | 2.2 (3.4) | 16.4 (35.0) | 0.9 (1.3) |
| Ferulate (FA) | 2 | 3 | 8 | 1 |
| Stilbenes (St) | 0 | 0 | 1 | 0 |
a
Percentages of γ-acetylated guaiacyl-syringaresinol complexes (C') are shown in parentheses.
b
Expressed as a fraction of the total lignin inter-unit linkage types.
c
Expressed as the number of units per 100 aromatic units; rounded percentages. The raw percentages, obtained earlier with nitrobencene oxidations, are shown in parentheses (obtained from the Supplementary Data in Reyes-Rivera et al., 2015).