Willd. ex Schult.
Turnera microphylla Ham.
Turnera diffusa, known as damiana, is a shrub native to southwestern Texas in the United States, Central America, Mexico, South America, and the Caribbean. It belongs to the family Passifloraceae.
Damiana is a relatively small shrub that produces small, aromatic flowers. It blossoms in early to late summer and is followed by fruits that taste similar to figs. The shrub is said to have a strong spice-like odor somewhat like chamomile, due to the essential oils present in the plant. The leaves have traditionally been made into a tea and an incense which was used by native people of Central and South America for its relaxing effects. Spanish missionaries first recorded that the Mexican Indians drank Damiana tea mixed with sugar for use as an aphrodisiac.
Damiana has long been claimed to have a stimulating effect on libido, and its use as an aphrodisiac has continued into modern times. More recently, some corroborating scientific evidence in support of its long history of use has emerged. Several animal testing studies have shown evidence of increased sexual activity in rats of both sexes. Damiana has been shown to be particularly stimulating for sexually exhausted or impotent male rats as well as generally increased sexual activity in rats of both sexes. It has also been shown that damiana may function as an aromatase inhibitor, which has been suggested as a possible method of action for its reputed effects.
Damiana might be effective as an anxiolytic.
Damiana is an ingredient in a traditional Mexican liqueur, which is sometimes used in lieu of Triple Sec in margaritas. Mexican folklore claims that it was used in the "original" margarita. The damiana margarita is popular in the Los Cabos region of Mexico.
Damiana contains damianin; tetraphyllin B; gonzalitosin I; arbutin; tricosan-2-one; p-cymene; β-sitosterol; 1,8-cineole; apigenin; α-pinene; β-carotene; β-pinene; eucalyptol; tannins; thymol; and hexacosanol.
In the state of Louisiana, Damiana is considered a "prohibited plant" along with 39 other plants by Louisiana State Act 159, effective 8 August 2005. Any combination of any of the parts, leaves, stems, stalks, seeds, materials, compounds, salts, derivatives, mixtures, preparations, or any resin extracted from any part of the plant is illegal to possess or distribute for human consumption in the state of Louisiana. This was due in part to an increase in the number of synthetic cannabis overdoses from a variety of chemically-infused plant material formulations, most of which contained Damiana as a primary ingredient.
A product known as "Black Mamba", labelled as containing "100% Damiana", has been on sale in the UK; ill effects from its use have been reported. MP Graham Jones has called for the substance to be made illegal. "Black Mamba" is a combination of damiana and various synthetic cannabinoid receptor agonists, including JWH-018. Synthetic cannabis has caused adverse side effects in a number of users. Damiana is considered safe when consumed in its natural form.
During Prime Minister's questions on Wednesday the 7th of March 2012 MP Nadhim Zahawi asked for action to be taken in relation to "Black Mamba", the Prime Minister responded:
- "We are determined to stamp out these so-called legal highs. The Home Office is aware of this particular drug. We now have the drugs early warning system which brings these things to our attention, but as he says, a decision needs swiftly to be made and I will make sure that happens." 
Black Mamba is now illegal in the UK.
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- Legislature of Louisiana: Regular Session, 2010; Act No. 565; House Bill No. 173
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- Black Mamba Spice: A Cannabinoid Cocktail
- Fake Weed, Real Drug: K2 Causing Hallucinations in Teens | LiveScience
- DAMIANA: Uses, Side Effects, Interactions and Warnings - WebMD
- David Cameron MP, Prime Minister of the UK, House of Commons, 7th March 2012.
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