Flammulina velutipes (commonly known as enoki or velvet shank mushroom) has been studied for its antioxidant properties, which are relevant to the mitigation of free radical damage. Several in vitro and animal studies have demonstrated that extracts from F. velutipes possess significant free radical scavenging abilities. These antioxidative effects are attributed to various bioactive compounds found in the mushroom, such as polysaccharides, phenolic compounds, and ergothioneine, a naturally occurring amino acid with known antioxidant functions.

For example, research published in peer-reviewed journals has reported that polysaccharide extracts from F. velutipes can increase antioxidant enzyme activities (such as superoxide dismutase and catalase) and reduce markers of oxidative stress in animal models. Additionally, some studies have shown that methanolic and aqueous extracts from the fruiting body exhibit dose-dependent DPPH and ABTS radical scavenging activity in laboratory assays.

However, most of the evidence is preclinical, and robust human clinical trials are lacking. Thus, while there is scientific interest and some validation in laboratory settings, the evidence is not strong enough to rate higher than 2 on the scale, as there is limited direct clinical evidence supporting its efficacy for treating or preventing free radical damage in humans.