ABSTRACT: The aim of this study was to classify some markers of common herbs used in Western
medicine according to the Biopharmaceutical Classification System (BCS). The BCS is a scientific
approach to classify drug substances based upon their intestinal permeability and their solubility, at
the highest single dose used, within the physiologically relevant pH ranges. Known marker
components of twelve herbs were chosen from the USP Dietary Supplement Compendium
Monographs. Different BCS parameters such as intestinal permeability (Peff) and solubility (Cs) were
predicted using the ADMET Predictor, which is a software program to estimate biopharmaceutical
relevant molecular descriptors. The dose number (D0) was calculated when information from the
literature was available to identify an upper dose for individual markers. In these cases the herbs were
classified according to the traditional BCS parameters using Peff and D0. When no upper dose could be
determined, then the amount of a marker that is just soluble in 250 mL of water was calculated. This
value, Mx, defines when a marker is changing from highly soluble to poorly soluble according to BCS
criteria. This biopharmaceutically relevant value can be a useful tool for marker selection. The present
study showed that a provisional BCS classification of herbs is possible but some special considerations need to be included into
the classification strategy. The BCS classification can be used to choose appropriate quality control tests for products containing
these markers. A provisional BCS classification of twelve common herbs and their 35 marker compounds is presented.
KEYWORDS: Biopharmaceutical Classification System, markers, herbs, herbal extracts, permeability, solubility, dose number