Screening of European medicinal herbs on their tannin content-New potential tanning agents for the leather industry

This work addresses European medicinal herbs as possible resources for vegetable tannins and their usage in leather production but also for further applications such as in the food, pharmaceutical or chemical industry. A detailed review of literature was conducted to identify herbs with promising tannin contents. 47 European medicinal herbs were identified for further analysis. Two plants from Rosaceae (Potentilla erecta and Geum urbanum) and one from Ericaceae (Arctostaphylus uva-ursi) show the highest tannin contents between 15 w% and 30 w% in literature. To verify the data from literature the identified 47 herbs were extracted and analyzed on their tannin content per plant by the radial diffusion method. 16 plants interfered with the radial diffusion method. Maximum tannin content per plant of 11,6 w% and maximum tannin content per dried extract of 38,4°w% were analyzed for Rubi fruticosus. For six plants of the sixteen plants it was possible to confirm the tannin contents from literature (Alchemilla vulgaris, Acrtostaphylus uva-ursi, Fragaria, Potentilla anserine, Potentilla erecta and Rubi fruticosus). For the remaining seven plants, lower tannin contents were obtained than listed in literature (Geum urbanum, Melissa officinalis, Mentha piperita, Origanum vulgare, Rubi idaei, Salicis folium and Vaccinium vitis-idaea). In the end, those six plants were evaluated on their theoretical availability in Germany as resource for new tanning agents. Fragaria, Alchemilla vulgaris and Rubi fruticosus showed the highest potential for application in leather production and for further applications. Highest amount of vegetable tannin extracts - up to 1900 kg/ha was estimated for Alchemilla vulgaris.