Despite tremendous efforts devoted to LCC studies, methods that preserve the existing LCC bonds quantitatively are still lacking. Recent developments in the quantitative LCC fractionation still contain one or more steps where alkaline solutions or strong bases are applied, which could cleave sensitive linkages. In the present work, a new protocol for the quantitative fractionation of lignin carbohydrate complexes (LCC) has been developed. The method is very mild when compared to previously described methods of quantitative fraction. The operations are performed at near-neutral pH conditions and low temperatures, the idea being to preserve as many of the native LCC linkages as is possible. The same protocol is applied to both hard and softwoods substantiating the universal application. The lignin-carbohydrate linkage analysis is another issue that requires attention since the direct analysis of LCC isolates by NMR techniques in the past indicate weak signal responses corresponding to their relative abundances, unless were cryogenic probes are applied. It is therefore of interest to obtain fractions enriched in LC- bonds to assure that some structures do escape analysis. To that end, the present protocol has achieved the separation of the lignin-free hemicelluloses from those attached to lignin, enriching LCC and allowing for the first time estimates of hemicelluloses fractions that are not attached to lignin in the studied woods. The enriched LCCs obtained thereof, have been studied by quantitative 2D HSQC NMR, thioacidolysis-<sup>31</sup>P NMR and GC MS techniques to unveil the differences in the lignin structure of LCCs. The presence of benzyl ethers, γ-esters and phenyl glycosides in the LCC samples are assigned according to the literature.

Global protocol for the mild quantitative fractionation of lignin carbohydrate complexes (LCC)

251st National Meeting (2016)

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