A Study on the Antioxidant Properties and Stability of Ergothioneine from Culinary-Medicinal Mushrooms

The naturally occurring amino acid ergothioneine (EGT) has excellent free radical scavenging ability, which was not different to ascorbic acid. The IC50 values for EGT scavenging hydrogen peroxide, hydroxyl radicals, and superoxide anions were 11.65 ± 0.31, 70.31 ± 1.59, and 160.44 ± 0.32 μg/mL, respectively. The EGT concentration in different species of mushrooms was significantly different (p < 0.05), but it was not significantly related to the ability of the mushrooms to scavenge reactive oxygen species (p > 0.05). After isolating EGT from mushrooms, we demonstrated that the antioxidant ability of EGT accounts for about 25% of the total antioxidant ability of the extract. We studied the stability of EGT and found that it has excellent light, thermal, and acid-base stability. However, the presence of Cu2+ decreased the concentration of EGT. Unlike EGT, the thermal stability of the EGT extracted from Pleurotus citrinopileatus (PEGT) was not as good as EGT, while long-term high-temperature heating caused a decrease in the concentration of PEGT. The results of our study provide a basis for further investigating EGT from mushrooms for research and development.