I always enjoy a good research challenge but was about to give up. It's helpful that my long-term memory is still intact.

Pygeum is a phyto-sterol and a precursor to the anabolic steroid known as Boldenone. The latter is made for use by veterinarians but not surprisingly professional sports players dope with it. Here is the neurology connection; Boldenon stimulates release of erythropoietin and that is now in research proving to be neuroprotective in a number of contexts including PD.

Here is a link explaining all potential benefits. I know this isn't exactly the same thing but it is definitely a building block to the steroid so this could be key to its protective properties..

Erythropoietin: a multimodal neuroprotective agent

Incidentally, our good friend Amgen has multliple patents on a compound with a basis that was used to treat anemia in Cancer patients.
of Erthropoietin.

Laura