The phytoequivalence of herbal extracts: A critical evaluation

The concept of phytoequivalence was developed in Germany in mid-1990 to indicate that a herbal extract is equivalent to another one, more specifically, to a clinically validated one. The pharmacological/physiological activity of an extract is related to its composition, but, due to the presence of many constituents, reliable technique are necessary to compare extracts. While the concept of equivalence among pure chemicals or isolated substances is feasible using the modern chromatographic and spectroscopic technology, specific guideline for herbal extracts or botanicals are still missing. This is mainly due to the multicomponent nature of the herbal extracts and to the natural variability of their constituents. Nevertheless, by using mathematical and/or chemometric approaches, the concept of phytoequivalence can be precisely addressed, as exemplified by a series of examples that are discussed in detail. Helpful practical recommendations based on literature data and personal experience are presented.