The Yohimbe tree is native to Africa and related to the coffee tree.
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The active ingredient is called the alkaloid yohimbine. Additionally, there are 31 alkaloids found in the tree.
How it works is, upon consumption, blood flow is restricted to the genitals, the veins are constricted thus, stopping the outflow of blood.
However, too much of a good thing can be bad, as using an excessive amount of Yohimbe has been associated with over-excitability, a rapid heartbeat and even death.