How could I quantify lingin S, G and H precursor monomers in plant tissue (arabidopsis, tomato)? Can someone suggest a method?
Please take a look of this paper: Chapter Compositional Variability of Lignin in Biomass
2.3.4. Analytical pyrolysis
Pyrolysis transforms a nonvolatile compound into a volatile degradation mixture by heat in the absence of oxygen and by the breaking of chemical bonds using thermal energy [54, 55]. The ground biomass sample (particle sizes from mm to μm) is heated at temperatures from 400 to 1000°C, in the absence of oxygen, for 300 s to less than 0.5 s, producing charcoal (solid), bio-oil (liquid) and fuel gas products [56, 57]. Analytical pyrolysis was perfected for the pyrolysis of small samples for analytical purposes: a mixture of volatile compounds derived from the three macromolecular constituents of biomass (cellulose, hemicelluloses and lignin) is obtained and separated through a capillary column, identified by mass spectrometry (MS) and quantified by a flame ionization detector (FID). The MS identification of pyrolysis products was mostly made by Faix et al. [58, 59, 60, 61] and by Ralph and Hatfield [62]. Nowadays, quantification is also made by Py-GC/MS [63]. Pyrolysis is particularly interesting to characterize the lignin monomeric composition into the phenolic S, G and H precursor monomers. The ratio of monomers is given in the form of H:G:S or, more frequently, as the S/G ratio.
This might be helpful: Article Quantification of Lignin and Its Structural Features in Plan...
Maybe you can use the NREL method, this technique is used to quantifie fibers like hemicellulose, lignin and cellulose.
Pyrolysis GC-MS, Potassium permanganate oxidation + GC, 13C NMR, old method is nitrobenzene oxidation + GC, may be for you would be enough just methoxyl group analysis
Article Whole plant cell wall characterization using 2D-NMR
Whole cell wall gel NMR is very nice. But a little bit demanding on equipment available and NMR time.
You can try dissolving a small sample (~25 mg) in 1 mL of reiterated solvent (DMSO, CDCl3, Acetone, water etc.). Then, you can do 1H-13C-2D-HSQC NMR analysis of this sample. There is literature available on correlating the signals from your results with the corresponding signals from S/G/H units of lignin. The area under the curve for these signals can give you the relative amount of S/G/H units. This method is more accurate.
Alternatively, you can perform a fast pyrolysis of this sample (in a reactor or in an instrument called 'Pyroprobe'). Then you can analyze and quantify the products using GC-MS. The ratio of products that have S/G/H type structures will give you an approximate idea of the S/G/H ratio in the original lignin. This method is less accurate.