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.
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.
Rehmannia contains the vitamins A, B, C, and D, as well as other compounds, such as an iridoidglycoside, 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.
The name "Rehmannia" has also been given to a genus of Jurassicammonites belonging to the Reineckeidae family.
Jim English (2010). "Traditional Chinese Herbs for Arthritis". Nutrition Review5 (2). Retrieved 2011-12-29.
Liu, J; He QJ, Zou W, Wang HX, Bao YM, Liu YX, An LJ (December 2006). "Catalpol increases hippocampal neuroplasticity and up-regulates PKC and BDNF in the aged rats". Brain Research1123 (1): 68–79. doi:10.1016/j.brainres.2006.09.058. PMID 17078935.Cite uses deprecated parameters (help)
"Rehmannia". The Plant List. Retrieved 7 October 2013.
Oxelman, B.; Kornhall, P.; Olmstead, R.G.; Bremer, B. 2005. Further disintegration of the Scrophulariaceae. Taxon 54 (2): 411-425.
Beardsley, P. M. & Olmstead, R. G. 2002. Redefining Phrymaceae: the placement of Mimulus, tribe Mimuleae, and Phryma.American Journal of Botany 89: 1093-1102 (available online)
Zhi Xia, Yin-Zheng Wang and James F. Smith 2009. Familial placement and relations of Rehmannia and Triaenophora (Scrophulariaceae s.l.) inferred from five gene regions, American Journal of Botany 96: 519-530(available online).