Tannins from four commonAcacia species of Texas and Northeastern Mexico

The amount of tannins present inAcacia berlandierii, A. farnesiana, A. greggii andA. rigidula, 4 common species of the southwestern United States and northern Mexico, was determined. Bark samples of the 4 species were extracted with water, 80% methanol, and 70% acetone. Of these, 70% acetone proved to be the most efficient solvent. Tannins were determined by Folin-Denis analysis for total phenolic materials, followed by precipitation with casein or hide powder. The hidepowder method was modified to facilitate handling of smaller samples. Results of tannin determination by casein and hide-powder precipitation methods gave comparable results. The amount of tannins present in leaves, bark, wood, and immature fruits of samples of these species was then determined by the same analytical methods. In most instances, bark and immature fruits had the highest percentage of tannins (5–15%) and wood was much lower (less than 1%). Leaves had intermediate values.