Comparative Neuroprotective, Anti-Inflammatory and Neurite Outgrowth Activities of Extracts of King Oyster Mushroom, Pleurotus eryngii (Agaricomycetes)

Pleurotus eryngii (king oyster mushroom) is a renowned culinary mushroom with various medicinal properties that may be beneficial for health maintenance and disease prevention. However, its effect on the nervous system remains elusive. In this study, hot water (PE-HWA) and ethanol (PE-ETH) extracts of P. eryngii were investigated and compared for their neuroprotective, anti-inflammatory, and neurite outgrowth activities in vitro. Based on the results, both extracts up to 400 μg/mL were nontoxic to PC12 cells and BV2 microglia (p > 0.05). Treatment with 250 μM hydrogen peroxide (H2O2) markedly (p < 0.0001) reduced the PC12 cell viability to 67.74 ± 6.47%. Coincubation with 200 μg/mL and 400 μg/mL of PE-ETH dose-dependently increased the cell viability to 85.34 ± 1.91% (p < 0.001) and 98.37 ± 6.42% (p < 0.0001) respectively, while PE-HWA showed no activity. Nitric oxide (NO) released by BV2 microglia was notably (p < 0.0001) increased by 1 μg/mL lipopolysaccharides (LPS) from 7.46 ± 0.73 μM to 80.00 ± 3.78 μM indicating an inflammatory reaction. However, coincubation with 200 and 400 μg/mL of PE-ETH significantly (p < 0.0001) reduced the NO level to 58.57 ± 6.19 μM and 52.86 ± 3.43 μM respectively, while PE-HWA was noneffective. PE-ETH and PE-HWA at 40 μg/mL significantly increased the neurite-bearing cells from 4.70 ± 3.36% to 13.12 ± 2.82% (p < 0.01) and 20.93 ± 5.37% (p < 0.0001) respectively. Pleurotus eryngii, particularly the ethanol extract (PE-ETH) and its potentially bioactive compounds, could be explored as a neurohealth promoting agent, due to its collective neuroprotective, anti-inflammatory, and neurite outgrowth activities.