Studies on Plant Metabolites

Morton, James J (1968) Studies on Plant Metabolites. PhD thesis, University of Glasgow.

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The work carried out was concerned with an investigation into a possible connection between the sugars present in a mucilagenous polysaccharide from bracken rhizomes and the sugars present in the glycolipid fraction from the same plant source. This work was initiated after a survey of the literature concerning the role of nucleoside diphosphate sugars in glycosidic bond formation and in particular polysaccharide synthesis, revealed a number of unexplained observations which suggested a possible involvement of a third group of sugar containing compounds. The nature of these observations inferred that the compounds involved could well be lipoidal in character, BRACKEN POLYSACCHARIDE. Part 1 of the thesis is devoted to a description of the extraction, purification and analysis of an acidic mucilagenous polysaccharide present in the rhizomes of the bracken plant (Pteridium aquilinum). The polysaccharide was extracted using a cold 5% solution of trichloroacetic acid and subsequently purified by repeated precipitation in alcohol followed by titration with a 10% solution of cetyl trimethyl ammonium bromide. The sugar content of the purified polysaccharide was analysed qualitatively by both paper and gas-liquid chromatography. The following sugars were detected: D-galactose, D-mannose, L-arabinose, D-xylose, L-fucose and a uronic acid. An investigation into the acidic function present revealed that it was probably entirely due to the uronic acid moiety. Sulphate content was shown to be very low and to decrease with purification, suggesting that its presence was due to contamination rather than as an integral part of the structure. Quantitative analysis of hoxose, pentose and methyl hoxose was performed using the colorimetric methods of Dische and Borenfreund. This showed that L-fucose was present in as much as 20% weight of the polysaccharide. GLYCOLIPID FRACTION. Part 2 of the thesis gives an account of the investigation carried out into the glycolipid fraction present in Bracken. Section A is devoted to a preliminary investigation into different methods of extraction and purification. These included the use of methanol and chloroform-methanol, 2:1 v/v, as extracting reagents. Various Bracken preparations were also used: fresh Bracken, Bracken preheated at 110 and freeze-dried bracken. These different trials were studied as to their effectiveness in reducing enzymic action during the extraction process. The purification processes studied included cellulose column chromatography for the removal of non-lipi contaminants, dialysis, and the diffusion of a chloroform-methanol mixture of the extract against a large excess of water, as used By Folch. A preliminary examination of the lipid-bound sugars present in the lipid mixture revealed D-glucose, L-galactose, D-mannose, L-arabinose, D-xylose and two unknowns, one of which was suspected of Being a sulphonated glucose. These results were confirmed By Both paper and gas-liquid chromatography. One of the major problems during this initial series of investigations was the difficulty in obtaining reproducible results, with regard to the kind and amount of sugars found. Confirmation of the sugars found in the glycolipid fraction was obtained from the work described in Section B of Part 2. This section is concerned with attempts to fractionate the lipid mixture, firstly By removing neutral lipids and other nonglycolipid material such as phospholipids, followed By the fractionation of the individual glycolipids themselves. This was performed after preliminary trials, using a combination of silicic acid, magnesium silicate and DEAE cellulose column chromatography. The fractions obtained were analysed for phosphorus and sugar content and they were also monitored using two dimensional thin-layer chromatography. After column fractionation the groups of purified glycolipids were finally separated into individual compounds by preparative thin-layer chromatography on silicic acid. The individual glycolipids were then analysed for sugar and fatty acid content by gas-liquid chromatography.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry, Agriculture
Date of Award: 1968
Depositing User: Enlighten Team
Unique ID: glathesis:1968-78473
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 28 Feb 2020 12:09
Last Modified: 28 Feb 2020 12:09

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