About Polygala tenuifolia Willd.
Polygala tenuifolia Willd., known as yuǎn zhì (Chinese: 远志, 遠志), is an herb species in the Polygalaceae family, and it is hardy to USDA Zone 6. Yuan zhi is primarily used as an expectorant. It is counted among the 50 fundamental herbs used in traditional Chinese medicine, where it is believed to have neuropsychiatric effects. It has been studied as a potential source of drugs for the treatment of depression and Alzheimer's disease. Herb quality of Polygala tenuifolia varies widely. As of 2020, there had been no toxicological studies or clinical trials on this herb. However, a meta-analysis published in March 2025, covering 27 studies, 2,334 samples and 19 natural extract treatments, reported that "[t]he most striking result was that the root extract of Polygala tenuifolia ... had the highest ranking for improving overall cognitive function".
