Date of Award

12-2012

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Biological and Pharmaceutical Sciences

First Advisor

Dr Michael Hall

Second Advisor

Dr Mary Concannon

Abstract

Horse chestnut residue was made available by a local pharmaceutical company. The residue was subjected to compositional analysis and studied to determine potential for residual biological activity, including prebiotic, antimicrobial, anti-hyaluronidase and anti-elastase effects.

The residue had 52 % total solids, including 2.97% ash, 6.93% protein, 1.89% crude fat. Oleic acid (74.7%) was the main fatty acid components in the crude lipid component. The major ash components were potassium, phosphorus, calcium and magnesium.

Prebiotic potential of aqueous extract (HCE) from horse chestnut residue was confirmed. A new formula for calculation of prebiotic index (PI) was developed. PI for probiotics (Lactobacillus and Bifidobacterium species) grown with HCE as main nutrient were determined and compared to PI of the commercial prebiotics FOS, GOS and inulin. The experiments confirmed horse chestnut extract as a potential prebiotic. The Lactobacillus and Bifidobacterium strains are able to metabolize the extract, the extent of which varied with individual strains. All probiotics grown with the horse chestnut extract exhibited positive prebiotic index (PI). B. breve obtained the highest PI (4.64±0.45). While 1% (w/v) crude horse chestnut residue was added to the media, only 0.16% was soluble. Commercial prebiotics (1% (w/v)) were 100% soluble. Results obtained for PI values for individual strains e.g. L. plantarum on GOS (1.03), FOS (0.82), inulin (-0.58) and HCE (0.52) would indicate that HCE has significant prebiotic potential at much lower concentrations that commercial prebiotics.

Probiotic strains grown with HCE produced lactic acid and/or acetic acid. For B. breve the pH was 5.90±0.02 after 24 hours which correlated to 6.09mM lactic and 20.05mM acetic acid. Similar results were obtained for other strains tested.

A novel microplate assay was developed to allow for high throughput screening for prebiotic potential and the prebiotic activity of lyophilised horse chestnut aqueous extract (lHCE) was tested under different processing treatments (exposure to low pH at ambient and high temperature and Maillard reaction).

The lHCE contained fructose, glucose, sucrose as well as oligosaccharides (determined by HPLC: Cation Exchange Chroatography). A new format of modified Dubois assay was developed for high throughput screening of carbohydrate content in FPLC fractions. Size exclusion chromatography of lHCE was used to establish an oligosaccharide of average molecular mass of 2735 Da.

Additional activities were also detected. The lHCE also had anti-hyaluronidase (IC50= 4.8mg/ml) and anti-elastase (IC50=50mg/ml) activity. Organic extracts from the residue demonstrated significant antimicrobial activity against E. coli ATCC 25922, E. aerogenes ATCC 13048 and S. aureus ATCC 9144. MIC of methanolic extract (MetHCE) was determined as 53mg/ml for E. coli.

Access Level

info:eu-repo/semantics/openAccess

Coverage

July 2024

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