Separation and characterization of lignin compounds from the walnut (Juglans regia) shell oil using preparative TLC, GC-MS and 1H NMR

The shell of the walnut is used as a filler by a variety of industries viz. cosmetic, paper and the adhesive. It is the lignin, present in the shell that enhances the utility of the walnut shell as binders, fillers, and resin extenders. The present study is aimed at the extraction and characterization of some important lignin compounds present in the walnut shell oil. The oil was extracted by a novel method in which the shells were roasted at 250-300degreesC. The lignin breakdown compounds of the oil were then isolated by solvent extraction using petroleum-ether (60-80 fractions), separated by preparative TLC and were fully characterized by employing GC-MS and H-1 NMR techniques. UV, FTIR and HPLC data was then used to confirm the structures. The major compounds arising from lignin breakdown are thus identified as guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-propylguaiacol, syringol, 4-methylsyringol, 4-ethylsyringol and 4-propylsyringol. (C) 2003 Elsevier B.V All rights reserved.