Tannin Contents of Selected Plants Used in Jordan

This study aimed at measuring the tannin contents of different plant species that are traditionally used in the Jordanian diet. Thirty nine selected plants belonging to 21 families and 37 genera were analyzed in this study. Tannin contents had not been determined in many of these species. Fresh samples were oven-dried and their tannin contents were chemically determined using Folin-Denis reagent method. The absorbance was measured by spectrophotometry at 760-nm wavelength and tannin content was calculated using a tannin-standard curve. Results showed that tannin contents of the analyzed species were highly variable, ranging from 25 mg/kg in plums and verbena to 42961 mg/kg in rosemary (on dry matter basis). It is therefore expected that due to variability in tannin content, different nutrition-health effects may result, a matter which requires other studies to clarify these effects.