Protein-bound polysaccharides from Amanita ponderosa cultures: characterisation, toxicological assessment and antioxidant properties

In recent years, protein-polysaccharide complexes extracted from mushrooms have received great attention from the scientific community, due to their medicinal properties, namely antioxidant, antitumor, antimicrobial, immunomodulatory, antiatherogenic and hypoglycaemic properties [1, 2]. The southern of Portugal, due to its Mediterranean climate and flora diversity, is a region with a high prevalence of wild edible mushrooms Amanita ponderosa [3]. The aim of this work was to produce and characterize the protein-polysaccharide complexes, extracted from cultures (mycelia or supernatants) of different strains of A. ponderosa in order to evaluate their biological activities. Batch cultures were performed during 15 days, and polysaccharides concentrations were determined by the phenol–sulphuric method. A combined FTIR-ATR (Fourier-transform infrared using the attenuated total reflection) and Raman spectroscopy was used for the screening of bioactive protein-polysaccharides compounds present in the culture extracts. FTIR-ATR and Raman spectra of protein-bound polysaccharides samples showed bands profile compatible with this type of compounds. The characterization and fractionated of polysaccharide-protein complexes, performed by SEC UV-IR-HPLC (HPLC Size Exclusion Chromatography, coupled to UV(280nm) and RI detectors), showed four major complexes, with different molecular weight. Extracts showed no toxicity against Artemia salina cultures. The polysaccharide-protein complexes showed antioxidant activity by DPPH and β-carotene/linoleic acid methods. Protein-polysaccharide complexes showed ability to mimitize the catalase enzymatic activity. Therefore, based on the observed biological properties, extracts of A. ponderosa cultures, could be an important source of bioactive compounds, with potential medicinal value.