Structural characterization of the lignin in the cortex and pith of elephant grass (Pennisetum purpureum) stems

J Agric Food Chem. 2012 Apr 11;60(14):3619-34. doi: 10.1021/jf300099g. Epub 2012 Mar 28.


The structure of the lignin in the cortex and pith of elephant grass (Pennisetum purpureum) stems was studied both in situ and in isolated milled "wood" lignins by several analytical methods. The presence of p-coumarate and ferulate in the cortex and pith, as well as in their isolated lignins, was revealed by pyrolysis in the presence of tetramethylammonium hydroxide, and by 2D NMR, and indicated that ferulate acylates the carbohydrates while p-coumarate acylates the lignin polymer. 2D NMR showed a predominance of alkyl aryl ether (β-O-4') linkages (82% of total interunit linkages), with low amounts of "condensed" substructures, such as resinols (β-β'), phenylcoumarans (β-5'), and spirodienones (β-1'). Moreover, the NMR also indicated that these lignins are extensively acylated at the γ-carbon of the side chain. DFRC analyses confirmed that p-coumarate groups acylate the γ-OHs of these lignins, and predominantly on syringyl units.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acylation
  • Coumaric Acids / analysis
  • Coumaric Acids / chemistry
  • Gas Chromatography-Mass Spectrometry
  • Hot Temperature
  • Lignin / analysis
  • Lignin / chemistry*
  • Lignin / isolation & purification
  • Magnetic Resonance Spectroscopy
  • Molecular Structure
  • Molecular Weight
  • Pennisetum / chemistry*
  • Plant Stems / anatomy & histology
  • Plant Stems / chemistry*
  • Propionates


  • Coumaric Acids
  • Propionates
  • Lignin
  • ferulic acid
  • p-coumaric acid