Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502392
Title: An investigation into the structure-function relationships of polysaccharides from Ganoderma applanatum
Author: Budala, Supriya
Awarding Body: University of Westminster
Current Institution: University of Westminster
Date of Award: 2008
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Abstract:
In this study, the structure-function relationships of the polysaccharides extracted from Ganoderma applanatum were investigated. This involved the extraction of polysaccharides, testing their immunomodulatory properties, structurally characterising the immunomodulatory polysaccharides and correlating the structures determined with their immunomodulatory activity. Three bio chemically different polysaccharide preparations obtained from both the fruiting body and cultured mycelium of G.applanatum using a sequential extraction method employing three solvents (water, ammonium oxalate and sodium hydroxide), under conditions of varying temperatures and pH accompanied by constant stirring. This 'mild to harsh' method of extraction facilitated the extraction of polysaccharides from the outermost to the innermost layers of the fungal cell wall. As markers of immunomodulation, the levels of stimulation/inhibition of reactive oxygen species, nitric oxide and tumour necrosis factor-alpha production by macrophages and neutrophils, were measured in the presence of the polysaccharide extracts. The polysaccharides extracted through different solvents had different immunomodulatory activities, which varied with their concentrations. In general, all mycelial polysaccharides had stimulatory effects on macrophages and neutrophils while the fruiting body polysaccharides had inhibitory effects. Composition and linkage analysis of the mycelial polysaccharides confirmed that they were composed of at least three species of hetero-polysaccharides (P-1,3-glucans, cc-1,4-glucans and C(- 1.6-mannans) with different degrees of branching. molecular weight:. anionic charge. monosaccharide composition and linkages. A significant finding from this study was that. with a variation in the conditions of extraction and the solvent used. the complexity of the polysaccharides changed. While polysaccharides with relatively low molecular weight:. fewer branches and low negative Charge were extracted under mild and neutral conditions. polysaccharides with higher molecular weight:. more branches and more negative charge were extracted under the harsh. alkaline conditions. Taking into account the higher reproducibility of the mycelial polysaccharides and their significant immunomodulatory activity compared with those from the fruiting bodies. the mycelial polysaccharides were further purified on the basis of charge and molecular weight The immunomodulatory effects of the purified low molecular weight neutral and charged sub-fractions of the mycelial extracts suggested that the negative charge of polysaccharides - due to the presence of uronic acids and low molecular weight - played a vital role in their activity. This study confirmed that the three-solvent sequential extraction method facilitates polysaccharide extraction from both the cultured mycelium and the fruiting bodies of G.applanatum. The composition and linkages of these extracts, which govern their solubility, conformation. charge. molecular weight:. degree of branching and degree of polymerisation, play a vital role in their immunomodulatory activity. G.applanatum polysaccharides modulate immune responses by triggering immune cell (macrophages/neutrophils) activation and cytokine induction by binding to carbohydrate specific receptors on macrophages and neutrophils. Based on all the analysis and inferences made during this study it was conclUded that (a) all mycelial and fruiting body polysaccharides are 'immunomodulators' and (b) the nature of the relationships between the polysaccharide structures and their immunomodulatory activity is specific to each fungal species and therefore, cannot be generalised, Mycelial polysaccharides from medicinal fungi such as G.applanatumcan therefore be used as health supplements, immune boosters or ac!juvants in radio- and/or chemo-therapy to improve the quality of life.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.502392  DOI: Not available
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