Icariin- Epimedium grandiflorum Morr

Name: Icariin
Synonym: 5-hydroxy-2-(4-methoxyphenyl)-8-(3-methylbut-2-enyl)-7-[(2S,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy-3-[(2S,3R,4R,5R,6S)-3,4,5-trihydroxy-6-methyloxan-2-yl]oxychromen-4-one
CAS: 489-32-7
Molecular Formula: C33H40O15
Molecular Weight: 676.66
Botanical Source: Epimedium grandiflorum Morr
Major Functions: The "active ingredient" in Epimedium is icariin, 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 . Other research has demonstrated that injections of Epimedium extract, directly into the penis of the rat results in an increase in penile blood pressure.
Like Viagra, icariin, the active compound in Epimedium, inhibits the activity of PDE-5. In vitro assays have demonstrated that icariin inhibits PDE-5 with an IC50 of around 1 micromolar, while Viagra has an IC50 of about 6.6 nanomolar (.0066 micromolar) and Levitra has an IC50 of about 0.7 nanomolar (.0007 micromolar). Measured differently, the EC50 of icariin is approximately 4.62 micromolar, while Viagra is .42 micromolar. The amount of oral administration of Epidemium extract necessary to achieve these relative concentrations is unclear from the literature, and may not be relevant if the herb works through multiple mechanisms, as has been suggested. 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.