Did not know about the piperezine and urea - also piperazine is an effective parasite killer, it stuns them. I think that piperidine (from black pepper) is the natural form.
Wiki:
Piperazines were originally named because of their chemical similarity with piperidine, part of the structure of piperine in the black pepper plant (Piper nigrum). It is important to note, however, that piperazines are not derived from plants in the Piper genus.