Stability testing on typical flavonoid containing herbal drugs.

The aim of the presented work was to examine possible changes in the flavonoid pattern of common flavonoid containing herbal drugs during long term and stress testing storage periods. HPLC fingerprint was used to demonstrate the differences in stability of individual flavonoid components. In addition, the total flavonoid content was determined according to the pharmacopoeial photometrical method. Drug material was stored according to the ICH-guidelines at 25 degrees C and 60% rh (relative humidity) for long term testing over a 24 months period or at 40 degrees C and 75% rh under stress conditions for 6 months. Increased temperatures of 80 degrees C and 100 degrees C were chosen to elucidate possible instabilities of selected flavonoids. As an overall result, during long term testing, no significant changes in the flavonoid pattern can be detected. However, some flavonoid containing herbal drugs (e.g. birch leaves), showed a decrease of most flavonoids when stored at high temperature by an increase in the respective aglycones. Similar results were obtained during storage at 40 degrees C/75% rh.