Fenugreek dopamine enhancement
As a rule of thumb, anything that can be used in the treatment of Parkinson's disease also has potential to enhance libido.
The most obvious example is L-dopa, the standard medication for those afflicted by Parkinson's. The scientific literature is full of references that attest to hypersexual behavior in elderly people who take L-dopa to contain Parkinson's symptoms.
There is a good number of additional pharmaceutical products that can be used in addition to L-dopa to treat Parkinson's disease, such as lisuride, pergolide, bromocriptine, cabergoline, etc. None of them have proven more effective than L-dopa but when tolerance develops towards L-dopa, they are used as an adjuvant therapy. The downside of these additional medicines is that they often cause serious nausea. As a matter of fact, many of them also work as emetics, meaning they induce vomiting.
On the other hand, fenugreek (Trigonella foenum?graecum) has been shown in a double-blind, placebo-controlled study to significantly enhance the effectiveness of L-dopa in Parkinson's disease.
Here a link to the study:
Apart from the scientific proof for the effectiveness of fenugreek in the amelioration of Parkinson's, there is a large body of thousands of reports of anecdotal evidence that fenugreek enhances sexual desire and sexual experience.
The most credible scientific proof for the libido-enhancing effect of fenugreek is cited in the following article published in the Washington Post: