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Monitoring Phenolic Composition of Maturing Maize Stover by High Performance Liquid Chromatography and Pyrolysis/Gas Chromatography/Mass Spectrometry*
Author(s) -
Galletti Guido C,
Bocchini Paola,
Smacchia Ana M,
Reeves III James B
Publication year - 1996
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/(sici)1097-0010(199605)71:1<1::aid-jsfa535>3.0.co;2-a
Subject(s) - chemistry , lignin , nitrobenzene , chromatography , high performance liquid chromatography , gas chromatography , pyrolysis , alkali metal , potassium hydroxide , extraction (chemistry) , mass spectrometry , hydroxide , organic chemistry , catalysis
Maize stovers collected every 14 days over an 84‐day growth period were subjected to high‐performance liquid chromatography with electrochemical detector (HPLC‐ED) and pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) in order to monitor changes in the phenolic composition. Prior to HPLC‐ED analyses, ground samples were sequentially extracted with (i) methanol, (ii) 0·1 M sodium hydroxide and (iii) 2 M sodium hydroxide in the presence of nitrobenzene to separate, respectively, free phenolic monomers, alkali‐labile phenolic monomers and alkali‐resistant lignin. In turn, solution (ii) was treated with alkaline nitrobenzene to obtain (iv) alkali‐labile lignin. Pyrolysis was carried out on ground native samples by using a platinum heated filament pyrolyser. Increases in the absolute phenolic concentrations in the residues of 0·1 M sodium hydroxide extraction and in the ratio of alkali‐resistant lignin vs total lignin were observed by HPLC‐ED during the first 28–42 days of maturation, reaching a steady level in the remaining maturation period. A linear increase of syringyl units vs guaiacyl units was for found the alkali‐resistant lignin fraction over the entire period of maturation. Similar trends were showed by PY/GC/MS with regard to relative lignin content and syringyl/guaiacyl ratio. Both techniques showed their usefulness to gauge changes in the phenolic composition during the lignification process.