Does total tannin content explain the use value of spontaneous medicinal plants from the Brazilian semi-arid region?

Due to the current predatory exploitation and consequent extinction of native medicinal plants around the world, strategies have been proposed aiming at the sustainable use of these resources. Accordingly, this study aims at verifying the differences in tannin compounds content in the bark of eleven species with high use value (UV) and also relating the amounts of tannins with their therapeutic indications. To quantify the total phenolic content in the samples the Folin-Ciocalteu reagent was used, and for total tannins chemical casein precipitation was applied. The amount of tannins ranged intra-specifically and the greater variation was found for Anadenanthera colubrina(angico) that displayed between 157.57 and 107.39 mg/g. The lowest variation occurred in Lafoensia replicata(mangabeira) with values ranging between 76.55 and 68.96 mg/g. There were significant differences between several of the eleven species and according to the simple regression analysis, the quantities of tannins found failed to justify their UV. Thus, it was not possible to establish whether the amount of total tannins influenced to a greater or lesser degree in the accumulation of knowledge. Moreover, this is the first study to investigate the relationship between the amount of total tannins and local botanical knowledge expressed by the UV