Bio compounds of edible mushrooms: in vitro antioxidant and antimicrobial activities

The aim of this study was to optimize the extraction of total phenolics from edible mushrooms, evaluate the in vitro antioxidant and antimicrobial activities and identify the main phenolic compounds present in the extracts. A Box-Behnken design was used and the effects of temperature (X1, 25-55 degrees C), solvent-to-solid ratio (X2, 30-70 mL per gram) and solvent concentration (X3, 25-75%) were evaluated. In the optimum conditions of extraction, the antioxidant (DPPH, ABTS and FRAP assays) and antimicrobial activities of the extract were tested against the bacteria: Bacillus cereus, Staphylococcus aureus, Escherichia coli and Salmonella enteritidis. In addition, the phenolic compounds of the extracts were quantified. The A. brasiliensis mushrooms showed the higher phenolic contents (13.16 mgGAE/g) and antioxidant activity by DPPH and ABTS assays of 50.64 and 128.60 mu molTE/g, respectively, among the phenolic extracts of the mushrooms analyzed. The gallic acid was the main phenolic compound identified and the A. brasiliensis had the highest concentration (491.89 mu g/g). All extracts presented antibacterial activity for Gram-positive strains (MIC <= 200 mg/mL). The high content of antioxidant compounds, extracted by a non-toxic solvent, suggested that the A. brasiliensis extract can be applied in the food industry as a natural antioxidant.