A RMN como ferramenta principal na determinação estrutural de polissacarídeos obtidos do cogumelo Pleurotus ostreatus (“shimeji”)
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2018-12-07
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Universidade Federal de Goiás
Resumo
The worldwide use of mushrooms for food and nutritional purposes has made the cultivation of these basidiomycetes an economically viable alternative. Research has been reporting the use of these fungi as good sources of vitamins, minerals, proteins and carbohydrates, in addition to their use involving biotechnological and pharmacological applications. Among the species of mushrooms cultivated in Brazil, Pleurotus ostreatus, known as shimeji, stands out, which is one of the most cultivated in the world. In this work, the difference in the composition of polysaccharides of the species Pleurotus ostreatus when cultivated in different substrates was analyzed. To analyze the chemical profile and carry out the structural characterization of the isolated macromolecules, was used as the main tool nuclear magnetic resonance spectroscopy - NMR. Therefore, were isolated from the fruiting body of P. ostreatus cultivated in wheat/corn/soybean (control substrate), a partially methylated monogalactan (fractions SF3CW-Po and QRPF3CW-Po) and β-glucan (SF2K-Po fraction), by successive aqueous and alkaline extractions, followed by fractionation through the freeze/thaw process, precipitation of the water soluble fractions with Fehling's solution and dialysis in membranes with a 500 kDa exclusion limit. The chemical structure was determined through analyzes of mossacaridic composition, sodium periodate oxidation, methylation, HPSEC and NMR. The SF2K-Po fraction suggested the presence of a β-D-glucan previously described for basidiomycetes, which contains a main chain formed by 3-O-β-D-Glcp units and can be substituted in O-6 by non-reducing terminals of β-Glcp (1 branch every three major chain units), possibly distinguishing between water solubility and size (molar mass) and the SF3CW-Po and QRPF3CW-Po one fractions partially methylated monogalactan (MG), with a molar mass of 14.144 x 103 g.mol-1, which has a core consisting of 6-O-α-D-Galp and 6-O- (3-O-Me -α-D-Galp), both being partially substituted at O-2 by 3-O-β-D-Manp. In order to verify whether the culture medium influences the production of these macromolecules, an experimental design was carried out to examine the effect of temperature, time and power conditions that maximize the extraction of these polymers using the microwave technique (MAE). The characterization and chemical profile of the extracts of P. ostreatus cultivated in six different substrates showed that both had the polymers isolated in the control substrate, however they can differentiate in the proportion of branching and molecular mass (Mw). Considering the importance of polysaccharides isolated from basidiomycetes, techniques for cultivating these fungi and characterization methods should be evaluated, since they present a promising source of bioactive molecules.
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Cogumelos medicinais , Pleurotus ostreatus , Monogalactana metilada , β-glucanas , Caracterização química , Micro-ondas (MAE) , Ressonância magnética nuclear - RMN , Medicinal mushroom , Pleurotus ostreatus , Methylated monogalactan , β-glucans , Chemical structure , Microwave assisted extraction (MAE) , Nuclear magnetic resonance – NMR
Citação
SILVA , E. V. A RMN como ferramenta principal na determinação estrutural de polissacarídeos obtidos do cogumelo Pleurotus ostreatus (“shimeji”). 2018. 146 f. Tese (Doutorado em Química) - Universidade Federal de Goiás, Goiânia, 2018.