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Abstract Milled wood lignins (MWL) were isolated from the stem (MWL S ) and pith (MWL P ) of bamboo ( Phyllostachys pubescens ). The nonacetylated and acetylated bamboo MWLs were investigated by Fourier transform infrared, quantitative 13 C-nuclear magnetic resonance (NMR), 2D heteronuclear single quantum coherence (HSQC) NMR, and 31 P-NMR spectroscopy. The MWL consists of p -hydroxyphenyl (1–2%), guaiacyl (21–31%), and syringyl (67–78%) units associated with p -coumarates and ferulates. A modified quantitative 13 C-NMR and 2D-HSQC analysis has demonstrated that the predominant intermonomeric linkages are of the type β- O -4 (45–49 per 100 C 9 units, i.e., per C 900 ) along with small amounts of other structural units such as resinols (3.6–7.4 per C 900 ), tetrahydrofuran (2.0–2.3 per C 900 ), phenylcoumaran (2.8–4.5 per C 900 ), spirodienones (1.3–2.3 per C 900 ), and α,β-diaryl ethers (2.8–2.9 per C 900 ). MWL P contained more p -coumarates than MWL S . The various degrees of γ-acylation (17–27%) were positively associated with S/G ratios in the lignins; however, γ-acylation was inversely correlated to the ratio between β-β and β- O -4 side chains in these lignin fractions. Moreover, a flavonoid compound (tricin) was also detected in the MWL S but not in MWL P . The two MWLs are very similar in terms of molecular weights and the contents of OH phen and OH aliph .
Wen et al. (Fri,) studied this question.