ABSTRACT
Bioavailability is the rate and extent to which a substance enters systemic circulation and becomes available at the required site of action. The impact of bioavailability in drug discovery and development is even more pronounced with products intended for oral use, whereby gastro-intestinal absorption constitutes the primary barrier between an active ingredient and systemic circulation. The drug must cross the epithelial barrier of the intestinal mucosa for it to be transported from the lumen of the gut into the systemic circulation and exert its biological actions. There are many anatomical and biological barriers that must be overcome for the oral drug delivery system to penetrate the epithelial membrane. Many natural compounds from medicinal plants have the capacity to augment bioavailability when co-administered with another drug. The drug discovery process has been highly aided by cthrough reverse pharmacology with new means of identifying active compounds and an accompanying reduction of drug development cost.
