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Table 1 Chemical shifts (δ13C1H) (ppm) of lignin components assigned in this study (DMSO-d 6 and pyridine-d 5 = 4:1)

From: Precipitate obtained following membrane separation of hydrothermally pretreated rice straw liquid revealed by 2D NMR to have high lignin content

   α(7) β(8) γ(9) 2 3 5 6
Aromatic region Syringyl     104.5/7.03, 104.5/6.94, 104.5/6.84    104.5/7.03, 104.5/6.94, 104.5/6.84
  Guaiacyl     111.7/7.21   116.0/7.17, 116.1/7.08, 115.1/7.02, 114.9/6.88, 115.0/6.79 116.0/7.17, 116.1/7.08, 115.1/7.02, 114.9/6.88, 115.0/6.79
        119.5/7.06, 119.5/6.97, 119.1/6.88 119.5/7.06, 119.5/6.97, 119.1/6.88
  p-Hydroxyphenyl     128.3/7.30, 129.8/7.33    128.3/7.30, 129.8/7.33
  Ferulate   111.6/7.42, 115.7/6.45      123.6/7.22
  p-Coumarate 145.4/7.73    130.5/7.66, 130.3/7.60, 130.3/7.54, 130.3/7.48 116.2/6.95, 114.5/6.64, 114.1/6.51, 114.0/6.41 116.2/6.95, 114.5/6.64, 114.1/6.51, 114.0/6.41 130.5/7.66, 130.3/7.60, 130.3/7.54, 130.3/7.48
Aliphatic side chain Cinnamyl alcohol    61.9/4.26     
  β-O-4 73.0/5.16, 72.2/5.10, 72.3/5.04       
  β-O-4-H/G (erythro) 71.2/4.97 84.9/4.44 60.8/3.44     
  β-O-4-H/G (threo)   84.1/4.52 60.7/3.82     
  β-O-4-S   86.7/4.25      
  β-5 87.4/5.64 52.2/3.73      
  5-5/4-O-β 83.2/5.11 87.7/3.62      
  1. Methoxyl groups were assigned at 56.1/3.92 and 56.0/3.77 ppm