Extractio, purification, characterization and bioactivities of polysaccharides isolated from selected Namibian mushrooms
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Date
2019
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Publisher
University of Namibia
Abstract
Mushrooms are considered as one of the notable functional foods for human consumption that have been cultivated and gathered for hundreds of years. The usage of mushrooms has expanded to a wide extent not only as food but also in the area of pharmaceuticals and nutraceuticals. In particular, mushrooms have been appreciated and consumed for both their nutritional value and medicinal properties. Bioactive molecules, particularly polysaccharides (PS) from mushrooms have been the subject of intense research, taking into account their high potential for application in different sectors. Mushroom polysaccharides (MPS) are not only important as prebiotics, but possess other biological properties such as antitumor, antimicrobial, antioxidant, immunomodulatory, antiviral and hypoglycemic effects. Despite this interest, no one to the best of my knowledge has studied the prebiotic properties of the Namibian wild edible mushrooms namely, Kalaharituber pfeilii and Termitomyces schimperi. Hence, this study is a preliminary attempt to elucidate the bioactivities of K. pfeilii and T. schimperi PS for potential application in functional food and nutraceuticals. Water and alkali PS extracts of K. pfeilii and T. schimperi were extracted and purified using Freimund’s method. The PS were chemically analysed by thin layer chromatography (TLC) and Fourier transform infra-red for monomeric sugar composition and functional groups determination. Additionally, the PS’s total carbohydrate and total phenolic content were evaluated using Phenol-Sulfuric acid method. Their antioxidant activity was evaluated using DPPH assay as well as by reducing power assay. Furthermore, the PS’s prebiotic activity was determined by the ability to lower the medium pH and increasing biomass of three probiotic strains: Lactobacillus plantarum ATCC 8014, Lactobacillus acidophilus ATCC 4356 and Enterobacter aerogenes. K. pfeilii hot water extracts had the highest contents of total carbohydrates / reducing sugars with 261.8 μg/200μL. In terms of monosaccharide composition, alkali and water extracts of T. schimperi were mostly composed of glucose, fructose and minor proportions of sucrose. Both T. schimperi and K. pfeilii’s alkali and water PS showed good scavenging activities against DPPH radical in a dose dependant manner in all concentrations studies. The scavenging ratio at high concentration of KPA and KPW were 48.1% and 41.5% respectively. Whereas, the scavenging ratio of TSA and TSW were 52.1% and 56.3% respectively. TSA, KPW and TSW showed their ability to act as carbohydrate source for the studied bacteria. This research may be an important first step for the design of PS with bioactivities that may be used in new health therapeutics and/or incorporation in functional foods or dietary supplements to infer health benefits and used as complementary or alternative medicine resource.
Description
A mini thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science (Microbiology)
Keywords
Extraction, Purification, Mushrooms