glycoside

   A plant compound containing one or more alcohols or sugars and a biologically active compound. The sugar part is called a glycone, the other stuff is called an aglycone. The important things to remember about some glycosides is that they may pass through much of the intestinal tract, with the hydrolysis of the molecule only occurring in the brush borders of the small intestine. The result is that the bioactive part, the aglycone, is absorbed directly into the bloodstream, and is often not floating around the intestinal tract contents at all. Quinones are irritating and even toxic when ingested, but when taken as glycosides, they are absorbed directly into the bloodstream, where they are not dangerous (in moderation), and get excreted in the urine, where they inhibit infections. Plants like Madrone, Uva Ursi, and Manzanita work in this fashion. Some plant-derived heart medicines are only safe in proper doses because they, too, are glycosides, and they can be carried safely bound to proteins in the bloodstream, whereas if the aglycone were in the free form in the gut it might be either toxic or be digested directly into an inactive form.