for concentrates, I find it best to get dried herb straight from a reputable source in thailand and prepare the extract yourself.  supplements are largely unregulated and what you are getting may be well above or below what is listed on the label.  When made yourself, you always know.

Alcohols are great for extracting plants into.  I use vodka for extracts that I will use orally, and isopropyl for transdermal applications.  to concentrate your extracts further just allow some of the alcohol to evaporate after you strain them