IMPORTANCE OF CONCOMITANT COMPOUNDS IN PL ANT-EXTRACTS

Plant extracts are multi-composed mixtures that can be subdivided into main active substances and concomitant compounds. Concomitant compoun ds are called co-effectors because they can change the physicochemical properties of the main active substances and therefore influence the biopharmaceutical parameters, e.g. solubility and bioavailability. The composition and the properties of plant extracts depend on a multitud e of different factors such as quality and degree of reduction of the plant, and the process of extraction and drying. Concomitant compounds affect the physical and chemical stability of plant extracts. The hyg roscopicity also depends on the composition of the concomitant compoun ds. It is an important property for the further processing of the plan t extract to solid dosage form, e.g. tablets. Solubility and dissoluti on rate can be influenced by the concomitant compounds. Both propertie s are important for the absorption of the active substances though in many cases the responsible substances and mechanisms are still unknown . Solubilisation by surface active agents, formation of soluble drug-c oncomitant compound-associates and solid dispersion, in which the drug is finely dispersed or X-ray amorphous, are often responsible for the increased solubility. Improved wettability in the presence of the con comitant compounds results in better dissolution. Supersaturated solut ions of the active substances are stabilized for months by inhibition of crystallization. Numerous examples are known for influencing the ab sorption by natural concomitant compounds. The absorption is enhanced by the increased amount of dissolved drug or by the alteration of memb rane permeability. Adsorption or complex formation with the concomitan t compounds decrease the absorption rate, in some cases also the exten t of absorption.