The complexity of herbal drugs – a scientific challenge

Objective

In phytotherapy parts of plants (drugs) and their pharmaceutical preparations (herbal medicinal products, HMPs) are used for the prevention, cure and relief of diseases. Generally, phytotherapy is based, without any exceptions, on the actual scientific medical standard. HMPs are obliged to match the same international standards with regard to quality, effectiveness and safety as chemically defined drugs. Nevertheless they are different as they are complex mixtures of many substances

thereby raising special challenges, e.g. in the registration of new HMPs.

Materials and methods

The literature was searched for theories and examples reflecting the complexity of HMPs.

Results

1. HMPs usually have more than one active (and very often still unidentified) principle.
2. The therapeutic effect of HMPs is the net result from various biopharmaceutic and pharmacologic effects, which can be synergistic or antagonistic, therefore:
   • dose-response curves can be misleading
   • the results of in vitro assays cannot be interpreted as in vivo concentrations of relevant ingredients are unknown
   • removing complete groups of substances from an extract can result in a substantial change of the therapeutic effect.
3. The combination of drugs multiplies the complexity but seems to simplify the treatment of complex diseases.

Conclusion

The search for synergistic or antagonistic effects of herbal drug components should be intensified as this knowledge can be used for improving effectiveness and/or safety. Also, as according to drug law each component of a drug combination must add to effectiveness or improve safety, this knowledge could save long-term empirically proven drug combinations from elimination.