Olive Leaf Extract

I am trying to research something that a friend of mine has told me about. He and his mother use Olive Leaf Extract. He swears by this; said he started using it when he had kidney stones and says it will cure anything.
I cannot find anything on the olive leaf extract. Do you know anything about it or where I might find info on it? This is very interesting to me and I would like to find out more about it. If you can lead me in the right direction or know anything about this being a medicinal herb, I would appreciate it. I happened to come across your website while looking for this.

Andrew Chevallier says in his book, "The Encyclopedia of Medicinal Plants" (available from Richters), that there is clinical evidence that olive leaves lower blood pressure. He says that they improve the circulatory system, they have a mild diuretic action, and that the leaves "may be used to treat conditions such as cystitis." According to Chevallier, the leaves contain oleoropine, oleasterol, and leine, but it is not clear to us whether these are responsible for the medicinal effects reported.
So, yes, it is possible that an olive extract could have a beneficial effect on kidney stones, but it may be an exaggeration to say that "it will cure anything."