Lignins detection

FIGURE 9.31 Analysis of lignin. Columns PSS PFG 100 + 1000. Eluent HFIP + 0.1 /VI KtFat. Temp 2S°C. Detection Rl. Calibration PSS PMMA ReadyCal kit. 

When testing for a tannin reserve or tannin index, the presence of natural color aids detection. Testing for tannin is simple and relatively accurate using either a permanganate reduction test (development of permanent purple color) or lignin/tannic acid polymer test (tungstate blue color). 

In our investigations, we also detected the sorption of isoPO from potato, Arabidopsis and wheat, by calcium pectate. Moreover, we observed the binding with calcium pectate of potato PO from the fraction of proteins ionically bound with cell walls. It is likely that the ability of some PO isoforms to bind with pectin ensures the spatial proximity of these enzymes to the sites of the initiation of lignin synthesis and that these "pectin-specific" isoforms take part in this process. 

Through these works, Wan has conclusively demonstrated that the photodehydration of hydroxybenzyl alcohols is a general reaction, and a wide variety of quinone methides can be photogenerated and detected using this method. Quinone methide photogeneration via this method has been shown to have importance in the photochemistry of Vitamin B641,42 and in model lignins 43... 

The method allowed the authors to characterise a pine pitch (viscous tar derived from the distillation of wood of pine trees). The main constituents detected by headspace SPME result from the pyrolysis of the lignin, guaiacol (11) and its p-w-alkyl derivatives [methyl... 

As to the origins of the major N compounds identified, it is possible that at least a portion of some of these compounds are pyrolysis products of amino acids, peptides, proteins, [18] and porphyrins (a component of chlorophyll), [19] or originate from the microbial decomposition of plant lignins and other phenolics in the presence of ammonia. [20] Of considerable interest are the identifications aromatic and aliphatic nitriles. Nitriles can be formed from amines with the loss of 2 H2, from amides with the loss of H20, and also by reacting n-alkanoic acid with NH3. [21] The detection of long-chain alkyl- and dialkyl-nitriles points to the presence in the soil or SOM of long-chain amines... 

The malodorous emission in this case appears to be dominated by volatile fatty acids and cresol. It is interesting to note in passing that cresol is one of the few odour-intensive species found in almost all odorous emission so far encountered. This osmogene is usually present in sufficient quantities to be clearly detectable of the odour port. Cresol and phenol (only found occasionally) is reported to be formed by the decomposition ol lignin. 

Several groups have identified non-radioactive metabolic intermediates of lignification in cambial sap or sapwood extracts 54, 58 b, 68). The compounds detected agree well with the schemes for the biosynthesis of lignin precursors set forth in Figs. 1 and 2 and with the data described later for the third stretch of lignification. 

Evidence for the participation in lignification of radicals in the form Rfl was not obtained from lignols extracted from simulated lignification experiments with coniferyl alcohol in vitro. Actually more direct proof was obtained here structures, e.g. (XII), that must have arisen from this form of the coniferyl radical were isolated from natural lignins by mild hydrolysis (see Section I). So far only structures derived from combinations of Rd type radicals with Rj, t5rpe radicals have been isolated 47, 705, 776, 777), but evidence for combinations of Rd radicals with Ra radicals has been secured by the detection of 40-(3,4-dimethox3q)henyl)-... 

Validation of the role of femloyl-CoA in the synthesis of the vanillin precursor will be detection of the appropriate intermediates and/or enzyme activities in placental extracts that could account for the production of the predicted levels of capsaicinoids. The presence of low levels of monolignol intermediates could be explained by lignin biosynthesis. An alternate route from phenylalanine to vanillin has been considered by some investigators Orlova et al. [68] demonstrated the role of the benzenoid pathway in petunia flowers for the biosynthesis of phenylpropanoid/benzenoid volatiles. 

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