Epimedium
Epimedium, also known as Rowdy Lamb Herb, Barrenwort, Bishop's Hat, Fairy Wings, Horny Goat Weed, or Yin Yang Huo (Chinese: 淫羊藿), is a genus of about 60 or more species of herbaceous flowering plants in the family Berberidaceae. The large majority are endemic to southern China, with further outposts in Europe,[1] and central, southern and eastern Asia.
Epimedium species are hardy perennials. The majority have four-petaled "spider-like" flowers in spring. Many are believed to be aphrodisiacs, particularly horny goat weed.[2]
Cultivation
Some varieties and hybrids have been in Western cultivation for the last 100 to 150 years. There are now a wide array of new Chinese species being cultivated in the west, many of which have only recently been discovered, and a number 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 new 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 or 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.
Hybrids include Epimedium versicolor (see illustration).
Propagation
While they can be successfully propagated in early spring, Epimedium are best divided in late August, with the aim of promoting rapid re-growth of roots and shoots before the onset of winter. Several breeders (in particular Darrell Probst, Tim Branney & Robin White) have also undertaken their own hybridization programmes with the genus Epimedium. Various new nursery selections are gradually appearing in the nursery 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, Epimedium 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 Epimedium will form beautiful ground cover 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.
Flower forms
From the gardeners point of view Epimedium flowers comprise two main parts, the inner sepals, which are petal-like and four in number (the four outer sepals are small, insignificant, and rapidly shed as the flowers open) and the petals, which are held within the sepals. In some species these petals have developed long spurs and in such plants they greatly exceed the size of the surrounding sepals, producing a flower shaped like an inverted crown, and also giving rise to one of the common names for Epimedium- bishops hat. In other species, however, (such as E. perraldianum) the petals are reduced to tiny spurs, and it is the greatly enlarged and highly coloured sepals that have expanded to catch the attention of the wandering insect.
Medicinal uses
Aphrodisiac
Many species of Epimedium have aphrodisiac qualities associated with content of icariin. According to legend, this property was discovered by a Chinese goat herder who noticed sexual activity in his flock after they ate the weed. 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.
The "active ingredient" in Epimedium is icariin,[3] which can be found in standardized extracts from 5% up to 60% potent. Strengths above that are usually reserved for lab use.
Icariin is 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.[4] Other research has demonstrated that injections of Epimedium extract directly into the penis of the rat results in an increase in penile blood pressure.[5]
Like sildenafil (the erectile dysfunction drug commonly sold as Viagra), icariin, the active compound in Epimedium, inhibits the activity of PDE-5. In vitro assays have demonstrated that icariin weakly inhibits PDE-5 with an IC50 of around 1 μM,[6][7] 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).[8] Measured differently, the EC50 of icariin is approximately 4.62 μM, while sildenafil's is .42 μM.[9] With the weak potency of Epimedium, and its unknown oral bioavailability, the amount of Epidemium extract necessary to have any effect is unclear from the literature.
A recently published Italian study modified icariin structurally and investigated a number of derivatives.[10] Inhibitory concentrations for PDE-5 close to sildenafil could be reached. Moreover, the most potent PDE-5 inhibitor of this series was also found to be a less potent inhibitor of phosphodiesterase-6 (PDE-6) and cyclic adenosine monophosphate-phosphodiesterase (cAMP-PDE), thus showing it to have more specificity for PDE-5 than sildenafil.
Epimedium has been shown to up-regulate genes associated with nitric oxide production and changes in adenosine/guanine monophosphate balance in ways that other PDE5 inhibitors do not. Epimedium may have potential to help sexual dysfunction and osteoporosis.[11]
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 and/or chemical formula for sildenafil. [12]
Osteoporosis
Animal studies indicate that Icariin also stimulates osteoblast activity in bone tissue, leading to the development and marketing of medicinal products based on Epimedium extracts for treatment of osteoporosis.[13][14][15][16][17][18]
Chemistry
Epimedium wushanense,contains a number of flavanoids. A total of 37 compounds were characterized from the underground and aerial parts of the plant. Among them, 28 compounds were prenylated flavonoids. The predominant flavonoid, epimedin C, ranged from 1.4 to 5.1% in aerial parts and 1.0 to 2.8% in underground parts.[19]
Literature
- Epimedium Care and Culture(Heronswood Nursery)
- William T. Stearn, The Genus Epimedium, revised edition 2002, ISBN 0-88192-543-8
- An Overview of Epimedium, in The Plantsman, March 2010, by Tony Avent of Plant Delights Nursery
References
- ^ "Epimedium Linn". Flora of Pakistan.
- ^ "Horny Goat Weed may offer [[Viagra]] alternative". www.meeja.com.au. 2008-09-30. Retrieved 2008-09-30.
{{cite web}}: URL–wikilink conflict (help) - ^ PubChem Entry for Icariin.
- ^ Chiu JH, Chen KK, Chien TM et al. Epimedium brevicornum Maxim extract relaxes rabbit corpus cavernosum through multitargets on nitric oxide/cyclic guanosine monophosphate signaling pathway. Int J Impot Res. 2006;18:335-42. PMID 16395327
- ^ Chen KK, Chiu JH. Effect of Epimedium brevicornum Maxim extract on elicitation of penile erection in the rat. Urology. 2006;67:631-5. PMID 16527595
- ^ Ning H, Xin ZC, Lin G et al. Effects of icariin on phosphodiesterase-5 activity in vitro and cyclic guanosine monophosphate level in cavernous smooth muscle cells. Urology 2006;68:1350-4. PMID 17169663
- ^ Xin ZC, Kim EK, Lin CS et al. Effects of icariin on cGMP-specific PDE5 and cAMP-specific PDE4 activities. Asian J Androl. 2003;5:15-8. PMID 12646997
- ^ Saenz de Tejada I, Angulo J, Cuevas P et al. The phosphodiesterase inhibitory selectivity and the in vitro and in vivo potency of the new PDE5 inhibitor vardenafil. Int J Impot Res. 2001;13:282-90. PMID 11890515
- ^ Jiang Z, Hu B, Wang J et al. 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 Technolog Med Sci. 2006;26:460-2. PMID 17120748
- ^ Dell'Agli M, Galli GV, Dal Cero E et al. Potent Inhibition of Human Phosphodiesterase-5 by Icariin Derivatives. J Nat Prod. 2008;71 Sep 9. [Epub ahead of print]. PMID 18778098
- ^ Huiping Ma, Xirui He, Yan Yang, Maoxing Li, Dingjun Hao, Zhengping Jia.,"The genus Epimedium: An ethnopharmacological and phytochemical review" Review Article Journal of Ethnopharmacology Volume 134, Issue 3, 12 April 2011, Pages 519-541
- ^ Board of Patent Appeals Affirms Rejection of Pfizer’s Broad Patent over ED Treatment
- ^ Yin XX, Chen ZQ, Liu ZJ, Ma QJ, Dang GT (2007). "Icariine stimulates proliferation and differentiation of human osteoblasts by increasing production of bone morphogenetic protein 2". Chin. Med. J. 120 (3): 204–10. PMID 17355822.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Zhang G, Qin L, Shi Y (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. doi:10.1359/jbmr.070405. PMID 17419678.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Chen KM, Ge BF, Liu XY; et al. (2007). "Icariin inhibits the osteoclast formation induced by RANKL and macrophage-colony stimulating factor in mouse bone marrow culture". Pharmazie. 62 (5): 388–91. PMID 17557750.
{{cite journal}}: Explicit use of et al. in:|author=(help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Huang J, Yuan L, Wang X, Zhang TL, Wang K (2007). "Icaritin and its glycosides enhance osteoblastic, but suppress osteoclastic, differentiation and activity in vitro". Life Sci. 81 (10): 832–40. doi:10.1016/j.lfs.2007.07.015. PMID 17764702.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Zhang DW, Cheng Y, Wang NL, Zhang JC, Yang MS, Yao XS (2008). "Effects of total flavonoids and flavonol glycosides from Epimedium koreanum Nakai on the proliferation and differentiation of primary osteoblasts". Phytomedicine. 15 (1–2): 55–61. doi:10.1016/j.phymed.2007.04.002. PMID 17482445.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Qin L, Han T, Zhang Q; et al. (2008). "Antiosteoporotic chemical constituents from Er-Xian Decoction, a traditional Chinese herbal formula". J Ethnopharmacol. 118 (2): 271–9. doi:10.1016/j.jep.2008.04.009. PMID 18501540.
{{cite journal}}: Explicit use of et al. in:|author=(help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ 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;