I am trying Damiana, too. Did some measurements beforehand, so I can compare.
When I am done testing, I will report back.
Meanwhile: the powder should be boiled (!) and then drunk (after cooling off).
But this stuff is so bitter, it almost makes me throw up.
I tried to mix it with yogurt, it tastes less evil, but still awful.
So now I will make pills of them, hoping it will easier on my taste buds and stomach.
It does not make me hornier so far. Which either says something about me or about the damiana.