Rehmannia

Rehmannia is a genus of six species of flowering plants in the order Lamiales, endemic to China.

The genus was included in the family Scrophulariaceae or Gesneriaceae in some older classifications. The current placement of the genus is in neither Scrophulariaceae s.s. nor Plantaginaceae s.l. (to which many other former Scrophulariaceae have been transferred). Earlier molecular studies suggested that its closest relatives were the genera Lancea and Mazus (Oxelman et al., 2005), which have been included in Phrymaceae (Beardsley & Olmstead, 2002). Subsequently it was found (Xie et al., 2009) that Rehmannia and Triaenophora are jointly the sister group to Lindenbergia and the parasitic Orobanchaceae.

Uses
Sometimes known as Chinese Foxglove due to its superficial resemblance to the genus Digitalis, the species of Rehmannia are perennial herbs. The plants have large flowers and are grown as ornamental garden plants in Europe and North America, and are used medicinally in Asia.

Known as dìhuáng (地黄) or gān dìhuáng (干地黄) in Chinese, R. glutinosa is used as a medicinal herb for arthritic conditions within Chinese traditional formulations.

Chemical constituents
Rehmannia contains the vitamins A, B, C, and D, as well as other compounds, such as an iridoid glycoside, catalpol, that has been shown to exert protective effects on dopaminergic neurons in aged rats to help inhibit microglial activation, thereby reducing the production of pro-inflammatory factors.

Homonym
The name "Rehmannia" has also been given to a genus of Jurassic ammonites belonging to the Reineckeidae family.

Species
Species include:
 * Rehmannia chingii
 * Rehmannia elata
 * Rehmannia glutinosa - (Gan) Di huang in Chinese
 * Rehmannia henryi
 * Rehmannia piasezkii
 * Rehmannia solanifolia