Procedures for the preliminary purification of plant nucleotide extracts before analysis by HPLC were evaluated for their efficiency in removing phenolics, pigments and other compounds which otherwise interfere. The extracts were obtained either by extracting with a monophasic mixture of methanol, chloroform, water and formic acid (12:5:2:1, by vol.), followed by re-extraction with methanol, water and formic acid (20:78:2, by vol.), or by extracting with 0.6 M perchloric acid followed by neutralization with tri-N-octylamine in Freon. The cleanest sample with respect to these interfering compounds was obtained using PVP (polyvinylpyrrolidone) batch treatment of a methanol:chloroform:formic acid extract followed by passage through a Cu<SUP>2+</SUP>-loaded Chelex column. This procedure also gave good recovery of nucleotides. Plant extracts were analysed for free nucleotides by HPLC using a weak anion-exchange microparticulate column (μBondapak NH_2) with a linear potassium phosphate gradient. The nucleotide contents of several fresh and processed plant foodstuffs were examined. Changes in the concentration of free nucleotides ascribable to food processing are discussed and in particular, reference is made to the observed changes in the concentrations of the nucleotide flavour-enhancers, GMP and IMP. Those changes which were attributed to processing, varied from tissue to tissue. In most cases, the differences in the concentration of GMP and/or IMP between unprocessed and processed tissue was > 20%. The data obtained from this survey were used to assess the total purine nucleotide content of a variety of common plant foodstuffs. For those foodstuffs analysed, the total purine nucleotide content ranged from 5 - 413 nmol.g^-1 tissue and, in foodstuffs which had been cooked, the purine nucleotide content had decreased by comparison with the uncooked foodstuffs. Quantitative analytical data for the free nucleotides of various mature and immature plant foodstuffs are discussed with special reference to the relationship of nucleotide profiles to the metabolic state of each tissue concerned. The HPLC studies were extended to include a preliminary examination of the occurrence of the pyrimidine glucoside 'vicine' in fresh and processed seeds of <i>Vicia faba</i> and other legume seeds. The results obtained represent the first documented occurrence of vicine in the mature dried seed tissue of <i>Glycine max</i> and <i>Phaseolus vulgaris</i>.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636363 |
| Date | January 1988 |
| Creators | Davies, D. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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