Just to confirm - both Silverweed and Ginko Bilboa are used in traditional medicines. Ginko Bilboa I think is available in pharmacies in Australia. Silverweed is comprised of 0.3% wet weight polyprenols, while mature ginko leaves are up to 2% dry weight polyprenols. I think someone mentioned that Ropren was 1% polyprenols and if that is the case (I am not sure it is), you might better off chewing on dried ginko leaves. The ref on the Ginko stuff is from pubmed and is as follows.