Epimedium

Epimedium
Epimedium × versicolor
Scientific classification
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Order: Ranunculales
Family: Berberidaceae
Genus: Epimedium
L.[1]
Type species
Epimedium alpinum
L.
Synonyms[2]

Epimedium, also known as barrenwort, bishop's hat, fairy wings, horny goat weed, or yin yang huo (Chinese: 淫羊藿), is a genus of flowering plants in the family Berberidaceae. The majority of the species are endemic to China, with smaller numbers elsewhere in Asia, and a few in the Mediterranean region.[2]

Epimedium species are deciduous or evergreen hardy perennials. The majority have four-parted "spider-like" flowers in spring.

The species used as a dietary supplement is Epimedium grandiflorum. It contains icariin, which is a weak PDE5 inhibitor in vitro. Its clinical effects are unknown.

Description

Epimedium alpinum flower; note the spurs almost as long as the sepals
Labelled flowers of E. × perralchicum 'Fröhnleiten'

Species of Epimedium are herbaceous perennials, growing from an underground rhizome. Their growth habits are somewhat variable. Some have solitary stems, others have a "tufted" habit, with multiple stems growing close together. There may be several leaves to a stem or the leaves may be solitary, produced from the base of the plant. Individual leaves are generally compound, often with three leaflets, but also with more. Leaflets usually have spiny margins. The leaves may be annual, making the plant deciduous, or longer lasting, so that the plant is evergreen. The inflorescence is an open raceme or panicle, the number of flowers varying by species.[2]

Individual flowers have parts in fours. There are four smaller outer sepals, usually greenish and shed when the flower opens. Moving inwards, these are followed by four larger petal-like inner sepals, often brightly coloured. Inside the sepals are four true petals. These may be small and flat, but often have a complex shape including a nectar-producing "spur" that may be longer than the sepals. There are four stamens.[2]

One of the common names for the genus, bishop's hat, arises from the shape of the flowers, particularly where the spurs are longer than the sepals.

Taxonomy

The genus was given its name by Carl Linnaeus in 1753, along with the European species E. alpinum.[1][3] The name is derived from a Greek word for a different plant, epimedion. The meaning of the original name is unclear.[4]

accepted species (65)[5]
  1. Epimedium acuminatum
  2. Epimedium alpinum
  3. Epimedium baiealiguizhouense
  4. Epimedium baojingensis
  5. Epimedium borealiguizhouense
  6. Epimedium brachyrrhizum
  7. Epimedium brevicornum
  8. Epimedium campanulatum
  9. Epimedium chlorandrum
  10. Epimedium circinatocucullatum
  11. Epimedium coactum
  12. Epimedium davidii
  13. Epimedium dewuense
  14. Epimedium diphyllum
  15. Epimedium dolichostemon
  16. Epimedium ecalcaratum
  17. Epimedium elatum
  18. Epimedium elongatum
  19. Epimedium enshiense
  20. Epimedium epsteinii
  21. Epimedium fangii
  22. Epimedium fargesii
  23. Epimedium flavum
  24. Epimedium franchetii
  25. Epimedium glandulosopilosum
  26. Epimedium grandiflorum
  27. Epimedium hunanense
  28. Epimedium ilicifolium
  29. Epimedium jingzhouense
  30. Epimedium koreanum
  31. Epimedium latisepalum
  32. Epimedium leptorrhizum
  33. Epimedium lishihchenii
  34. Epimedium lobophyllum
  35. Epimedium macrosepalum
  36. Epimedium membranaceum
  37. Epimedium mikinorii
  38. Epimedium multiflorum
  39. Epimedium myrianthum
  40. Epimedium ogisui
  41. Epimedium parvifolium
  42. Epimedium pauciflorum
  43. Epimedium perralderianum
  44. Epimedium pinnatum
  45. Epimedium platypetalum
  46. Epimedium pinnatum
  47. Epimedium pseudowushanense
  48. Epimedium pubescens
  49. Epimedium pubigerum
  50. Epimedium pudingense
  51. Epimedium qingchengshanense
  52. Epimedium reticulatum
  53. Epimedium rhizomatosum
  54. Epimedium sagittatum
  55. Epimedium sempervirens
  56. Epimedium setosum
  57. Epimedium shennongjiaensis
  58. Epimedium shuichengense
  59. Epimedium stellulatum
  60. Epimedium sutchuenense
  61. Epimedium trifoliolatobinatum
  62. Epimedium truncatum
  63. Epimedium wushanense
  64. Epimedium zhushanense

Hybrids

Epimedium × versicolor

Some artificial hybrids are cultivated in gardens. These include:[6]

Cultivation

Some varieties and hybrids have been in western cultivation for the last 100 to 150 years. There is now a wide array of new Chinese species being cultivated in the west, many of which have only recently been discovered, and some of which have yet to be named. There are also many older Japanese hybrids and forms, extending the boundaries of the genus in cultivation. Few genera of plants have seen such a dramatic increase in newly discovered species, primarily thanks to the work of Mikinori Ogisu of Japan and Darrell Probst of Massachusetts. The majority of the Chinese species have not been fully tested for hardiness nor indeed for any other aspect of their culture. The initial assumption that the plants would only thrive where their native conditions could be closely replicated have proven to be overly cautious, as most varieties are proving extraordinarily amenable to general garden and container cultivation.

Propagation

While they can be successfully propagated in early spring, epimediums are best divided in late summer, with the aim of promoting rapid re-growth of roots and shoots before the onset of winter. Several breeders (in particular Darrell Diano Probst, Tim Branney & Robin White) have also undertaken their own hybridization programmes with the genus. Various new nursery selections are gradually appearing in the horticulture trade, the best of which are extending the colour and shape range of the flowers available to the gardener.

Garden uses

Hugely popular as garden plants for centuries in Japan, epimediums are only just beginning to garner attention in the West. While they vary somewhat in their respective hardiness, all are essentially dwellers of the forest floor, and, as such, all require fundamentally similar conditions of moist, free-draining, humus-rich soil and cool shade, with some shelter for the newly emerging leaves. Some of the more robust varieties are often recommended as plants for dry shade, and whilst their tough foliage and stout rhizomes can allow them to grow successfully in such conditions, (and in more open, exposed positions too, in some instances) they will certainly not give their best. Furthermore, dryness and exposure will pretty much guarantee the early death of many of the newer and more delicate species.

Given suitable conditions most epimediums will form beautiful groundcover plants, often with magnificent new leaves tinted in bronze, copper and reds combining with a huge variety of flower colours and forms in spring. Handsome and dense-growing foliage remains present for much of the year, with the leaves often turning purple, crimson and scarlet in autumn in some forms, and remaining evergreen in others. With all varieties, however, the foliage is best cut off at ground level shortly before new leaves emerge, so as to fully reveal their beauty of form and colour. Ideally, a mulch should then be applied to protect the new growth from frosts.

Experimental

Erectile dysfunction

It is sold as a health supplement, usually in raw herb, tablet, or capsule form and sometimes blended with other supplements. The over-exploitation of wild populations of Epimedium for use in traditional Chinese medicine is having potentially serious consequences for the long-term survival of several species, none of which is widely cultivated for medicinal purposes.

Herbal epimedium contains icariin, which has demonstrated in vitro PDE5 inhibitory properties.[7] Sildenafil (an erectile dysfunction drug sold as Viagra) works by inhibiting the activity of PDE-5. Icariin is also purported to work by increasing levels of nitric oxide, which relax smooth muscle. It has been demonstrated to relax rabbit penile tissue by nitric oxide and PDE-5 activity.[8] Other research has demonstrated that injections of Epimedium extract directly into the penis of the rat results in an increase in penile blood pressure.[9]

In vitro assays have demonstrated that icariin weakly inhibits PDE-5 with an IC50 of around 1 μM,[10][11] while sildenafil has an IC50 of about 6.6 nM (.0066 μM) and vardenafil (Levitra) has an IC50 of about 0.7 nM (.0007 μM).[12] Measured differently, the EC50 of icariin is approximately 4.62 μM, while sildenafil's is .42 μM.[13] With the weak potency of epimedium, and its unknown oral bioavailability, whether orally administered epidemium extract has any effect is unclear from the literature.

Epimedium was used in a patent infringement case to rescind parts of the U.S. Viagra patent based on historic use in Chinese medicine. The specific claim was that Viagra was the first medical example of a PDE5 inhibitor which treated erectile dysfunction and therefore claimed patent protection from all similar PDE5 inhibitors. Patent examiners used epimedium as an example of prior use and rescinded those portions of the patent, however, the Viagra patent still protects the manufacturing process or chemical formula for sildenafil.[14]

Osteoporosis

There is one human trial looking at epimedium extract plus soy isoflavones on bone mineral density.[15]

Chemistry

Epimedium wushanense contains a number of flavanoids. 37 compounds were characterized from the underground and aerial parts of the plant. Among them, 28 compounds were prenylflavonoids. The predominant flavonoid, epimedin C, ranged from 1.4 to 5.1% in aerial parts and 1.0 to 2.8% in underground parts.[16]

References

  1. 1 2 "IPNI Plant Name Query Results for Epimedium". The International Plant Names Index. Retrieved 2013-05-11.
  2. 1 2 3 4 Ying, Junsheng; Boufford, David E. & Brach, Anthony R. (1994 onwards). "Epimedium". In Wu, Zhengyi; Raven, Peter H. & Hong, Deyuan. Flora of China (online). eFloras.org. Retrieved 2013-05-11. Check date values in: |date= (help)
  3. ↑ Linnaeus, Carl von. 1753. Species Plantarum 1: 117 in Latin
  4. ↑ Johnson, A.T. & Smith, H.A. (1972). Plant Names Simplified : Their Pronunciation Derivation & Meaning. Buckenhill, Herefordshire: Landsmans Bookshop. ISBN 978-0-900513-04-6.
  5. ↑ The Plant List 2013.
  6. ↑ Beckett, K., ed. (1993). "Epimedium". Encyclopaedia of Alpines : Volume 1 (A–K). Pershore, UK: AGS Publications. ISBN 978-0-900048-61-6. pp. 437–441.
  7. ↑ PubChem Entry for Icariin.
  8. ↑ Chiu, JH; Chen, KK; Chien, TM; et al. (2006). "Epimedium brevicornum Maxim extract relaxes rabbit corpus cavernosum through multitargets on nitric oxide/cyclic guanosine monophosphate signaling pathway". Int J Impot Res. 18 (4): 335–42. PMID 16395327. doi:10.1038/sj.ijir.3901437.
  9. ↑ Chen, KK; Chiu, JH (2006). "Effect of Epimedium brevicornum Maxim extract on elicitation of penile erection in the rat.". Urology. 67 (3): 631–5. PMID 16527595. doi:10.1016/j.urology.2005.09.051.
  10. ↑ Ning, H; Xin, ZC; Lin, G; et al. (2006). "Effects of icariin on phosphodiesterase-5 activity in vitro and cyclic guanosine monophosphate level in cavernous smooth muscle cells.". Urology. 68 (6): 1350–4. PMID 17169663. doi:10.1016/j.urology.2006.09.031.
  11. ↑ Xin, ZC; Kim, EK; Lin, CS; et al. (2003). "Effects of icariin on cGMP-specific PDE5 and cAMP-specific PDE4 activities.". Asian J Androl. 5 (1): 15–8. PMID 12646997.
  12. ↑ Saenz; de Tejada, I; Angulo, J; Cuevas, P; et al. (2001). "The phosphodiesterase inhibitory selectivity and the in vitro and in vivo potency of the new PDE5 inhibitor vardenafil.". Int J Impot Res. 13 (5): 282–90. PMID 11890515. doi:10.1038/sj.ijir.3900726.
  13. ↑ Jiang, Z; Hu, B; Wang, J; et al. (2006). "Effect of icariin on cyclic GMP levels and on the mRNA expression of cGMP-binding cGMP-specific phosphodiesterase (PDE5) in penile cavernosum.". J Huazhong Univ Sci Technology Med Sci. 26 (4): 460–2. PMID 17120748. doi:10.1007/s11596-006-0421-y.
  14. ↑ Board of Patent Appeals Affirms Rejection of Pfizer’s Broad Patent over ED Treatment
  15. ↑ Zhang G, Qin L, Shi Y (July 2007). "Epimedium-derived phytoestrogen flavonoids exert beneficial effect on preventing bone loss in late postmenopausal women: a 24-month randomized, double-blind and placebo-controlled trial". J. Bone Miner. Res. 22 (7): 1072–9. PMID 17419678. doi:10.1359/jbmr.070405.
  16. ↑ Li HF, Guan XY, Ye M, Xiang C, Lin CH, Sun C, Guo DA.,"Qualitative and quantitative analyses of Epimedium wushanense by high-performance liquid chromatography coupled with diode array detection and electrospray ionization tandem mass spectrometry." J Sep Sci. 2011 May 10;

Bibliography

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