Table 1.
Composition of the lignin aromatic units, S/G ratio, and relative abundance of main inter‐unit linkages of WCW, MWL, and REL.
|
Sample |
S[a] [%] |
S′[a] [%] |
G[a] [%] |
G′[a] [%] |
H[a] [%] |
FA[c] [%] |
pCA[c] [%] |
β‐O‐4[a] [%] |
β‐5[a] [%] |
β‐β[a] [%] |
S/G[a] |
|---|---|---|---|---|---|---|---|---|---|---|---|
|
WCW_Birch |
65 |
13 |
22 |
<1 |
1 |
<1 |
<1 |
57 |
1 |
3 |
3.5 |
|
REL_Birch |
68 |
9 |
22 |
1 |
1[b] |
<1 |
<1 |
58 |
3 |
8 |
3.4 |
|
MWL_Birch |
57 |
8 |
32 |
1 |
3 |
<1 |
<1 |
53 |
4 |
11 |
2.0 |
|
WCW_Pine |
0 |
0 |
91 |
2 |
7 |
<1 |
<1 |
34 |
11 |
2 |
– |
|
REL_Pine |
0 |
0 |
93 |
5 |
2[b] |
<1 |
<1 |
40 |
17 |
6 |
– |
|
MWL_Pine |
0 |
0 |
94 |
4 |
2 |
<1 |
<1 |
34 |
17 |
6 |
– |
|
WCW_Reed |
35 |
3 |
56 |
0 |
6 |
12 |
24 |
49 |
9 |
1 |
0.7 |
|
REL_Reed |
40 |
3 |
52 |
0 |
6[b] |
7.5 |
23 |
48 |
8 |
4 |
0.8 |
|
MWL_Reed |
41 |
3 |
53 |
0 |
3 |
3 |
20 |
45 |
9 |
4 |
0.8 |
|
WCW_Walnut |
38 |
6 |
32 |
<1 |
24 |
<1 |
<1 |
47 |
9 |
8 |
1.3 |
|
REL_Walnut |
50 |
4 |
34 |
1 |
11[b] |
<1 |
<1 |
50 |
7 |
10 |
1.6 |
|
MWL_Walnut |
39 |
5 |
40 |
2 |
15 |
<1 |
<1 |
48 |
13 |
10 |
1.1 |
[a] S=syringyl units; S’=syringyl with a α‐ketone structure; G=guaiacyl structure; G’=guaiacyl units with a α‐ketone structure; H=p‐hydroxylphenyl units; FA=ferulate; pCA=pcoumarate; β‐O‐4=aryl ether linkage; β‐β=resinols; β‐5=phenylcoumaran. The data was calculated by semi‐quantitative method and based on the total amount of C9 units, and the molar percentage was based on the integration of the signal at α position of the linkage divided by the total integration of S (1/2 S2,6), S’ (1/2 S’2,6), G (G2), G’(G’2), H (1/2 H2,6), S/G ratio obtained by (1/2 S2,6+1/2 S’2,6)/(G2+G’2) (see Figure 2 for structures). [b] As REL samples were contaminated with proteins and the signals of H2’6 units were overlapped with phenylalanine from residue protein, the integration of H units was based on the overlapped signals. The integration values for the H units might be slightly larger than their actual H units because of the overlap of Phe3,5, in particular for Birch_REL and Pine_REL. [c] FA (FA2) and pCA (1/2 pCA2,6) were calculated by C9 units (see [a]).