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Introduction: There has been an upsurge of interest in mushrooms, such as Pleurotus species, as an important source of bioactive compounds. Mycelia-submerged culture represents a promising approach to search new safe and healthy myco-products with standardized quality in addition to mushroom fruiting bodies. Methods: The study examined the in vitro antimicrobial, antitumor and antioxidant activities of a hotwater extract from Pleurotus sp. mycelium. The antimicrobial activity was screened through the activation of the microbial autolytic system of four bacteria and four yeast strains. The anti-proliferative effects on NB4 human leukemia cells were measured by flow-cytometry analyses. The antioxidant activity was investigated by the scavenging of DPPH and ABTS radicals, the reducing power and the inhibition of lipid peroxidation. Results: The extract activated the microbial autolytic system of eight strains: 7 autolyzing strains with intensity values (Is) ranging from 2.7% in Candida sp. to 36.1% in Saccharomyces cerevisiae. Thus, the microbial autolytic system of the strains tested (including Gram-positive and gram-negative bacteria as well as yeasts) could be activated in vitro by mycelial extract. Pleurotus extract reduced the viability of NB4 leukemia cells, particularly at the concentration of 200 μg/mL to 82% compared to control cells, and induced apoptosis demonstrated by an increase in annexin V-FITC+ cells (25% at 200 μg/mL). At 10 mg/mL, the extract showed the most potent scavenging effects for DPPH and ABTS radicals (96% and 55%, respectively) and the inhibition of lipid peroxidation (52%). The mushroom extract at 5 mg/ mL manifested reducing power of 1.105. Although carbohydrates (76.8%, w/w) appear to be the most important bioactive compounds, secondary metabolites, like phenolics, would also contribute to the antioxidant, antimicrobial and anti-proliferative activities. Conclusion: The hot-water extract obtained from Pleurotus mycelium, in light of its in vitro antimicrobial, antitumor and antioxidant effects could be considered a good candidate for developing nutraceuticals and for designing innovative myco-therapeutics and phytocosmetics applications.

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The study examined the radioprotective activity of an aqueous extract from Pleurotus ostreatus mycelium administered to Balb/c mice. Male mice were whole-body irradiated on day 0 ((60)Co, at 0.43 Gy/min) and divided into two groups. The extract was administered intraperitoneally to one group (100 mg/kg) on days - 10 to - 6 and - 2 to +1 with respect to the irradiation. The irradiated-control group was injected with saline solution; non-irradiated mice were used as negative controls. The radioprotective effect was evident by increases in bone marrow cellularity (5.1 × 10(6)/femur vs. 1.1 × 10(6)/femur in saline-control mice, p < 0.05), leucocyte counts (10.5 × 10(9)/L vs. 4.5 × 10(9)/L, p < 0.05), and spleen cellularity (11.2 × 10(7)/spleen vs. 6.2 × 10(7)/spleen, p < 0.05). The extract stimulated macrophage phagocytic activity as judged by a faster rate of carbon clearance in terms of absorbance ratios (1.62 vs. 2.01, p < 0.05). Therefore, this extract may be a candidate therapeutic agent with radioprotective activity for haematopoiesis damage, particularly to cells involved in immune function.