Rehmannia, also known as Di Huang, is a traditional Chinese herb. In USA, it is also known as Chinese foxglove.
Rehmannia contains the vitamins A, B, C, D, and catalpol etc.
The raw Rehmannia root is called as Sheng Di Huang. Sheng Di Huang is often used to clear the "heat" from your body. In Chinese Medicine, the root can also be cooked in red wine. Then it is known as Shu Di Huang (prepared Rehmannia). In Chinese herbal medicine, prepared Rehmannia is mainly used for enhancing yin.