ABSTRACT: Plant biomass has been suggested as an alternative to produce
bioethanol. The recalcitrance of plant biomass to convert cellulose into simpler
carbohydrates used in the fermentation process is partially due to lignin, but the
standard methods used to analyze lignin composition frequently use toxic solvents
and are laborious and time-consuming. MS imaging was used to study lignin in
Eucalyptus, since this genus is the main source of cellulose in the world. Hand-cut
sections of stems of two Eucalyptus species were covered with silica and directly
analyzed by matrix-assisted laser sesorption ionization (MALDI)-imaging mass
spectrometry (MS). Information available in the literature about soluble lignin
subunits and structures were used to trace their distribution in the sections and using
a software image a relative quantification could be made. Matrixes routinely used in
MALDI-imaging analysis are not satisfactory to analyze plant material and were
efficiently substituted by thin layer chromatography (TLC) grade silica. A total of 22
compounds were detected and relatively quantified. It was also possible to establish a
proportion between syringyl and guaiacyl monolignols, characteristic for each species.
Because of the simple way that samples are prepared, the MALDI-imaging approach
presented here can replace, in routine analysis, complex and laborious MS methods in
the study of lignin composition.