Comparative study of organic solvent-soluble and water-soluble lipophilic extractives from wheat [Triticum aestivum] straw, 2: Spectroscopic and thermal analysis
2002
Sun, R.C. (University of Wales, Bangor (UK)) | Tomkinson, J.
As a continuing study of six organic solvent-soluble lipophilic extractives and one water-soluble lipo-philic extract from wheat straw, seven extracts were further compared using Fourier transform-infrared (FT-IR) analysis, sup1 H and sup13 C nuclear magnetic resonance (NMR) spectroscopy, and thermal analysis. In the FT-IR spectra of two-thirds chloroform/one-third methanol, methyl tert-butyl ether (MTBE), hexane, petroleum ether, and dichlo-romethane extracts, a strong band at 1746cm**-1 is indicative of the ester carbonyl of triglycerides or steryl esters or waxes, whereas the occurrence of carboxylic carbonyl of free fatty acids or resin acids at 1712-1719 cm**-1 is verified in the spectra of two-thirds toluene/one-third ethanol and hot water extracts. Signals at 187.9, 178.4, and 173.3 ppm in the sup13 C NMR spectrum of MTBE extract correspond to carbonyl groups of resin acids, fatty acids, and fatty acid/steryl esters, respectively. All the extractives were to varying degrees thermally unstable at a temperature of about 200degC, and the melting temperature occurred at about 54degC.
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