Polygala tenuifolia, also known as Yuan Zhi, is a root used in Traditional Chinese Medicine.
It has traditionally been used for its protective effects on the brain.
Preliminary animal evidence suggests that Polygala tenuifolia has an antidepressant effect in rats. Polygala tenuifolia_ may improve cognition, but more research is needed to confirm this effect.
Rodent research suggests that Polygala tenuifolia is similar in mechanism and effectiveness to ketamine, which interacts with N-methyl-D-aspartic acid and its receptors. Rodent studies assessing Polygala tenuifolia’s anti-amnesiac and adaptogen-like properties suggest that the herb can increase the level of compounds responsible for brain growth, like nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF).
Though Polygala tenuifolia supplementation may slightly increase cognitive ability in elderly people, it has limited effect on healthy adults. Supplementing Polygala tenuifolia can improve spatial organization and recognition, but it does not improve short- or long-term memory formation, as measured by free or cued recall. Much more research is needed to determine if Polygala tenuifolia qualifies as a nootropic.